Execution of dynamically configured application service in access method-independent exchange

Abstract

The present invention provides a virtual network, sitting "above" the physical connectivity and thereby providing the administrative controls necessary to link various communication devices via an Access-Method-Independent Exchange. In this sense, the Access-Method-Independent Exchange can be viewed as providing the logical connectivity required. In accordance with the present invention, connectivity is provided by a series of communication primitives designed to work with each of the specific communication devices in use. As new communication devices are developed, primitives can be added to the Access-Method-Independent Exchange to support these new devices without changing the application source code. A Thread Communication Service is provided, along with a Binding Service to link Communication Points. A Thread Directory Service is available, as well as a Broker Service and a Thread Communication Switching Service. Intraprocess, as well as Interprocess, services are available. Dynamic Configuration Management and a Configurable Application Program Service provide software which can be commoditized, as well as upgraded while in operation.

Claims

Having thus described the invention, what it is desired to claim and thereby protect by Letters Patent is: What is claimed is:

1. In the Internet network, a method for a service provider to provide a software service to users, the method comprising a multiplicity of computers, each computer having a communication device, and each computer having an operating system with interfaces for communication connectivity and synchronization, comprising:

a) a user process of a user computer having access to the Internet through a physical communication provider, uses an Internet protocol to connect to a service provider process executing on a service provider computer, the service provider process includes replacing a first minor service with a second minor service, wherein the first minor service communicates state information to the user process, and the user process communicates the state information to the second minor service;

b) the user process sends a communication to a service provider process;

c) the user process receives a response from the service provider process;

d) the user process disconnects from the communication with the service provider process; and

e) the user is billed for the service.

2. The method of claim 1 wherein the user process causes an instance of the service to begin execution.

3. The method of claim 1 wherein the service provider process is a dynamically configured service which provides a primary service and one or more minor services.

4. The method of claim 3 wherein:

a minor service is provided by a third process of a third computer of the network; and the user process communicates with the minor service.

5. The method of claim 1 wherein the service provider process includes an operation specification which includes information representative of an operation to be performed immediately.

6. The method of claim 1 wherein the service provider process includes an operation specification which includes information representative of an operation to be performed at intervals of time.

7. The method of claim 1 wherein the service provider process includes an operation specification which includes information representative of an operation to be performed as the result of communication of a specified event to the user process.

8. The method of claim 1 wherein the service provider process includes an operation specification to locate a minor service.

9. The method of claim 1 wherein the service provider process includes an operation specification to load a minor service.

10. The method of claim 1 wherein the service provider process includes an operation specification to execute a minor service.

11. The method of claim 1 wherein:

the service provider process includes establishing a communication channel with a minor service; and the user process communicates with the minor service.

12. The method of claim 1 wherein the service provider process includes suspending the execution of a minor service.

13. The method of claim 1 wherein the service provider process includes resuming the execution of a minor service.

14. The method of claim 1 wherein the service provider process includes unloading a minor service.

15. The method of claim 1 wherein the service provider process provides notification that an event has occurred.

16. The method of claim 1 wherein the user process and the second process communicate using the Internet Protocol.

17. The method of claim 1 wherein the request is sent using an industry standard protocol.

18. The method of claim 1 wherein the network is a commercial network.

19. The method of claim 3 wherein a component of software provides the minor service.

20. The method of claim 19 wherein the component of software is stored in a shared library.

21. The method of claim 20 wherein the component of software is dynamically loaded.

22. The method of claim 19 wherein a thread of execution is created to execute the component of software.

23. The method of claim 3 wherein a process executing on a third computer provides a minor service.

24. In the Internet network comprising a multiplicity of computers, each computer having a communication device, and an operating system with interfaces for communication connectivity and synchronization, a method for a first process of an end user computer to configure a service, the method comprising:

the first process uses an operating system interface to receive a communication from a second process of a second computer of the network, the communication including a specification for the use of at least one service;

the first process disconnects from the communication with the second process; and

the first process accesses the specification and configures the use of said service.

25. The method of claim 24 wherein the specification is communicated to the first process according to a protocol.

26. The method of claim 25 wherein the second process executes on a second computer of the network.

27. The method of claim 26 wherein the specification is received using the Internet Protocol.

28. The method of claim 24 wherein the first process causes an instance of the service to begin execution in a separate address space.

29. The method of claim 24, wherein the first process is an application service providing a primary service and one or more minor services.

30. The method of claim 24 further comprising the use of a third process of a third computer of the network, the third process providing a minor service, wherein the first process communicates with the third process when the first process requires the use of the service provided by the third process.

31. The method of claim 24 wherein the specification includes information representative of an operation to be performed immediately.

32. The method of claim 24 wherein the specification includes information representative of an operation to be performed at a specified time, which may be an interval.

33. The method of claim 24 wherein the specification includes information representative of an operation to be performed as the result of an event.

34. The method of claim 24 wherein the specification includes information for locating a service.

35. The method of claim 24 wherein the specification includes instructions for loading a service.

36. The method of claim 24 wherein the specification includes instructions to execute a service.

37. The method of claim 24 wherein the specification includes at least one specification for communicating with a service.

38. The method of claim 24 further comprising converting at least a portion of the communication from a first data type to a second data type.

39. The method of claim 24 wherein the specification includes information for replacing a first service with a second service.

40. The method of claim 24 wherein the specification includes information for suspending the use of a service.

41. The method of claim 24 wherein the specification includes information for resuming the use of a service.

42. The method of claim 24 wherein the first process and the second process communicate using an industry standard protocol.

43. The method of claim 24 wherein the first process communicates using a hierarchy of protocols.

44. The method of claim 24 wherein the service is provided by a component of software stored in a shared library, and the first process uses one or more operating system interfaces to dynamically load the software into the address space of the process.

45. The method of claim 44 wherein a thread of execution is created to execute the component of software.

46. The method of claim 24 further comprising the use of a communication to initialize the state of the service.

47. The method of claim 24 further comprising registering the service as a communication point.

48. In the Internet network, a method for a service provider to provide a service to an end user of a user computer having access to the Internet through a physical communication provider, the method comprising a multiplicity of computers, each computer having a communication device, and each computer having an operating system with interfaces for communication connectivity and synchronization, comprising:

a first process of a user computer connects to a service provider process executing on a service provider computer;

the first process sends a request to the service provider service process, the request including criteria for selecting a service, and in response to receiving and accessing the communication, the service provider service provides the requested service;

the first process receives a response from the service provider process;

the first process disconnects from the communication with the service provider process; and

billing for the service.

49. The method of claim 48 wherein the service provider service selects at least one service satisfying the criteria, and causes an instance of the service to begin execution.

50. The method of claim 48 wherein the service provider service dynamically configures the service as providing a primary service and one or more minor services.

51. The method of claim 48 further comprising the service provider process communicating with a second service, in order to provide the service to the first process.

52. The method of claim 48 further comprising the use of a specification containing information representative of an operation to be performed immediately.

53. The method of claim 48 further comprising the use of a specification containing information representative of an operation to be performed at a specified time, which may be an interval.

54. The method of claim 48 further comprising the use of a specification containing information representative of an operation to be performed upon notification of an event.

55. The method of claim 48 further comprising the use of a specification to locate a service.

56. The method of claim 48 further comprising the use of a specification to load a service.

57. The method of claim 48 further comprising the use of a specification to execute a service.

58. The method of claim 48 further comprising:

the service provider service communicating communications from the user process to the service; and

the service provider service communicating communications from the service to the user process.

59. The method of claim 48 further comprising suspending the use of a service.

60. The method of claim 48 further comprising resuming the use of a previously suspended service.

61. The method of claim 48 further comprising replacing a first service with a second service.

62. The method of claim 48 further comprising the use of state information to initialize a service.

63. The method of claim 48 further comprising unloading a previously loaded service.

64. The method of claim 48 further comprising the use of at least one event to cause an operation to be performed.

65. The method of claim 48 wherein at least one input type understood by the requested service is not public information.

66. The method of claim 48 further comprising the service provider providing at least one component of software used by the first process.

67. The method of claim 48 wherein the criteria includes information to identify the user.

68. The method of claim 48 further comprising the use of a multiplicity of directory services.

69. The method of claim 48 wherein a component of software provides a service.

70. The method of claim 48 wherein the service provider process uses one or more operating system interfaces to dynamically load a component of software into address space of the first process.

71. The method of claim 70 wherein a thread of execution is created to execute the component of software.

72. The method of claim 48 wherein the service provider process communicates with a second service provider process on a third computer to provide the service.

73. The method of claim 48 further comprising the use of a service to provide an expanded description of a named representation.

74. The method of claim 48 further comprising the use of a service to associate a named representation with an entity providing a service.

75. The method of claim 48 further comprising the use of a hierarchy of protocols.

76. In the Internet a method for a service provider application service process executing on a service provider computer having an operating system with interfaces for communication connectivity and synchronization, and a communication device, to be responsive to a communication from a user application service process executing on an end user computer, the end user computer having an operating system with interfaces for communication connectivity and synchronization, a communication device, and physical communication to the Internet provided by a communication provider, the method comprising:

the service provider application service process receives a request communication communicated from the user application service process, the communication including information representative of criteria for selecting a service from a set of one or more registered services;

the service provider application service process accesses the request communication and interacts with the communication to select at least one accessible service satisfying the criteria;

the service provider application service process sends a response communication including information representative of the at least one accessible service, the response including the connectivity required to use the accessible service; and

the service provider application service process disconnects from the communication with the user application service.

77. In the Internet a method for a service provider application process executing on a service provider computer to be responsive to a communication from a user application process executing on an end user computer, the end user computer having an operating system with interfaces for communication connectivity and synchronization, a communication device, and physical connection to the network provided by a communication provider, the method comprising:

a) the service provider service application process receives a request communication communicated from the user application process, the communication including one or more unique identifiers assigned to the user during a subscription process;

b) the service provider application process accesses the request communication, validates the user, locates at least one accessible service, provides the requested service; and

c) the service provider application process disconnects from the communication with the user application process.

78. The method of claim 77 wherein the communication provider is at least one of:

a Regional Bell Operating Company,

a Long Distance Carrier,

a Cellular Network provider,

a signal-based communication provider,

a wireless communication provider, or

a cable industry communication provider.

79. In the Internet a method for a service provider application process executing on a service provider computer to be responsive to a request from a user application process executing on an end user computer, the end user computer having an operating system with interfaces for communication connectivity and synchronization, a communication device, and physical communication provided by a communication provider, the method comprising:

the service provider application process receives a request communication communicated from the user application process, the communication including information representative of criteria for selecting a service from a set of one or more registered services;

the service provider application process accesses the request communication and selects at least one accessible service satisfying the criteria; and

and in response thereto, the service provider application process provides the requested service.

80. The method of claim 79 wherein at least one input type understood by the service provider application process is not public information.

81. In the Internet, a method for a first service provider application service process executing on a first service provider computer to be responsive to a communication communicated from a second application service of a second computer of the network, the method comprising:

the first service provider application service receives a communication, and accesses the communication, the communication containing information representative of a request for a service;

and in response thereto, the first service provider application process uses one or more operating system interfaces to dynamically configure a service to satisfy the request.

82. The method of claim 81 wherein at least one input type understood by the service provider application process is not public information.

83. In the Internet, a method comprising:

a service provider application service executing on a service provider computer uses at least one operating system interface to receive a communication communicated from a user application process of an end user computer, said communication representative of a request for a service when an event occurs;

and in response thereto, the service provider process accesses the communication, records the request and provides a response communication intended for the user process; and

in response to the recorded event occurring, the service provider process provides the requested service.

84. The method of claim 83 wherein at least one input type understood by the service provider application process is not public information.

85. A system for a service provider to extend the service of an application program sold to an end user, for use with an end user computer, the end user computer having an operating system with interfaces for communication connectivity and synchronization, a communication device, and physical communication connectivity provided by a communication provider, the system comprising:

an application program configured to use one or more operating system interfaces for communication connectivity and synchronization to communicate with, and be responsive to received communications from, a service provided by the service provider if the service is available; and

a service configured for use on a service provider computer to be responsive to communications received from an application process, interact with the communication, and to send a response to the application process wherein the application process corresponds to said application program.

86. A system for a service provider to extend the services of software sold to an end user, for use with an end user computer, the end user computer having an operating system with interfaces for communication connectivity and synchronization, a communication device, and communication connectivity provided by a communication provider, the system comprising:

software configured by the service provider to use one or more operating system interfaces for communication connectivity and synchronization to communicate with, and be responsive to received communications from, the service provided by the service provider if the service is available, the received communication including instructions for using an accessible service; and

a service configured for use on the service provider computer to be responsive to communications received from an application process, interact with the communication, and to send a response to the application process to use an accessible service wherein the application process corresponds to said software.

87. The system of claim 86 wherein the accessible service provides a minor service to said application software, and wherein the accessible service is at least one of:

a function,

a thread,

a process,

a communication point providing a service,

a component of software,

a dynamically loadable object,

an operating system service, or

a service provided by at least one statement executed by a shell.

88. A system for a service provider to extend the services of software sold to an end user, for use with an end user computer, the end user computer having an operating system with interfaces for communication connectivity and synchronization, a communication device, and communication connectivity provided by a communication provider, the system comprising:

an application program configured to use a protocol to send a communication to, and receive a communication from, a service provider service if the service is available; and

a service configured for use on a service provider computer to be responsive to communications received from an application process, to interact with the communication, and to send a response to the application process including one or more statements for using at least one service, wherein the application process corresponds to said application program.

89. The system of claim 88 wherein the accessible service provides a minor service to said application process, and wherein the accessible service is at least one of

a function,

a thread,

a process,

a communication point providing a service,

a component of software,

a dynamically loadable object,

an operating system service, or

a service provided by at least one statement executed by a shell.

Description

BACKGROUND OF THE INVENTION RECEIVED

1. Field of the Invention

This invention relates to computer networks and communication management, and to the establishment of communication between various users and/or software applications.

2. Background Discussion

The term "The Information Superhighway" is commonly thought of as an extension of the Internet, a network linking hundreds of thousands of computer systems together and communicating via a standard protocol.

A computer network is simply a collection of autonomous computers connected together to permit sharing of hardware and software resources, and to increase overall reliability. The qualifying term "local area" is usually applied to computer networks in which the computers are located in a single building or in nearby buildings, such as on a college campus or at a single corporate site. When the computers are further apart the term "wide area network" may be used.

As computer networks have developed, various approaches have been used in the choice of communication medium, network topology, message format, protocols for channel access, and so forth. Some of these approaches have emerged as de facto standards, but there is still no single standard for network communication. The Internet is a continually evolving collection of networks, including Arpanet, NSFnet, regional networks such as NYsernet, local networks at a number of university and research institutions, a number of military networks, and increasing, various commercial networks. The protocols generally referred to as TCP/IP were originally developed for use through Arpanet and have subsequently become widely used in the industry. The protocols provide a set of services that permit users to communicate with each other across the entire Internet.

A model for network architectures has been proposed and widely accepted. It is known as the International Standards Organization (ISO) Open Systems Interconnection (OSI) reference model. (See FIG. 10.) The OSI reference model is not itself a network architecture. Rather it specifies a hierarchy of protocol layers and defines the function of each layer in the network. Each layer in one computer of the network carries on a conversation with the corresponding layer in another computer with which communication is taking place, in accordance with a protocol defining the rules of this communication. In reality, information is transferred down from layer to layer in one computer, then through the channel medium and back up the successive layers of the other computer. However, for purposes of design of the various layers and understanding their functions, it is easier to consider each of the layers as communicating with its counterpart at the same level, in a "horizontal" direction. (See, e.g. The TCP/IP Companion, by Martin R. Arick, Boston: QED Publishing Group 1993, and U.S. Pat. No. 5,159,592. These, and all patents and publications referenced herein, are hereby incorporated by reference.)

As shown in FIG. 10, the lowest layer defined by the OSI model is called the "physical layer," and is concerned with transmitting raw data bits over the communication channel. Design of the physical layer involves issues of electrical, mechanical or optical engineering, depending on the medium used for the communication channel. The second layer, next above the physical layer, is called the "data link" layer. The main task of the data link layer is to transform the physical layer, which interfaces directly with the channel medium, into a communication link that appears error-free to the next layer above, known as the network layer. The data link layer performs such functions as structuring data into packets or frames, and attaching control information to the packets or frames, such as checksums for error detection, and packet numbers.

The Internet Protocol (IP) is implemented in the third layer of the OSI reference model, the "network layer," and provides a basic service to TCP: delivering datagrams to their destinations. TCP simply hands IP a datagram with an intended destination; IP is unaware of any relationship between successive datagrams, and merely handles routing of each datagram to its destination. If the destination is a station connected to a different LAN, the IP makes use of routers to forward the message.

The basic function of the Transmission Control Protocol (TCP) is to make sure that commands and messages from an application protocol, such as computer mail, are sent to their desired destinations. TCP keeps track of what is sent, and retransmits anything that does not get to its destination correctly. If any message is too long to be sent as one "datagram," TCP will split it into multiple datagrams and makes sure that they all arrive correctly and are reassembled for the application program at the receiving end. Since these functions are needed for many applications, they are collected into a separate protocol (TCP) rather than being part of each application. TCP is implemented in the "transport layer," namely the fourth layer of the OSI reference model.

Except as otherwise is evident from the context, the various functions of the present invention reside above the transport layer of the OSI model. The present invention may be used in conjunction with TCP/IP at the transport and network layers, as well as with any other protocol that may be selected.

As shown in FIG. 10, the OSI model provides for three layers above the transport layer, namely a "session layer," a "presentation layer," and an "application layer," but in the Internet these theoretical "layers" are undifferentiated and generally are all handled by application software. The present invention provides for session control and for communicating with applications programs. Thus the present invention may be described in accordance with the OSI theoretical model as operating at the session layer and application layers.

"Connectivity" and "convergence" have been used to describe two aspects of the communications and computing revolution taking place. In 1994, technology provides to communicate by telephone, pager, fax, email, cellular phone, and broadcast audio and video. However, to use these communication services, you have to employ a telephone number, beeper number, pager number, fax number, cellular number, and each of many email IDs, radio stations and television channels. The user is confronted with an overabundance of methods providing such physical connectivity, one which will only grow in the future.

The types of physical connections are provided by various systems including the Regional Bell Operating Companies, the Long Distance Carriers, the Cellular Networks, and others providing signal-based or wireless communications. The Cable Television Industry provides connectivity for video signals and increasingly other services.

SUMMARY OF THE INVENTION

The present invention provides a virtual network, sitting "above" the physical connectivity and thereby providing the administrative controls necessary to link various communication devices via an Access-Method-Independent Exchange. In this sense, the Access-Method-Independent Exchange can be viewed as providing the logical connectivity required. In accordance with the present invention, connectivity is provided by a series of communication primitives designed to work with each of the specific communication devices in use. As new communication devices are developed, primitives can be added to the Access-Method-Independent Exchange to support these new devices without changing the application source code. When viewed in accordance with the OSI model, the communication primitives operate at the level of the transport layer, and, to the extent appropriate, at the network layer, and in some instances down to the data link layer, and occasionally as needed, the physical layer.

Using the Access-Method-Independent Exchange of the present invention, anybody can provide a service. Similarly, anybody can be a client of a service. A service can even be a client of another service. This is because every user and every service is identified by a unique communication identifier. In accordance with the present invention, various communication points are connected together to form a communication link.

The aforesaid identifiers are assigned to the user, or service provider, during their subscription process. For service providers, additional information must be provided and added to the Thread Directory Service. This information includes the required physical connectivity to reach the service.

When users want to access the Access-Method-Independent Exchange, they simply supply Exchange with their unique identifiers. The Binding Service validates each user and permits access to the Exchange. The user may then connect to any registered service by simply calling the service's communication identifier. Of course, if they are unfamiliar with the service providers communication identifier, they can request assistance through the Thread Directory Service. The Thread Directory Service provides a listing of available services grouped by relationship. The user can search for keywords, titles, or other information such as service fees. Ultimately, the user can request to gain access to the service.

The Access-Method-Independent Exchange is not limited to servicing a particular geographic area and hence can easily work with foreign countries. The Access-Method-Independent Exchange includes the ability to provide voice or data message processing.

Access-Method-Independent Exchange Components: A Technical Overview The Thread Communication Service

At the core of the technology is the Thread Communication Service (TCS), a software utility used to administer the dynamic communications between computer processes executing on a local computer, or, on a remote system. Two versions of the TCS have been implemented: one for intraprocess communications and a second for interprocess communications. The intraprocess version of the TCS is used for a single application process with multiple threads of control. The interprocess version of the TCS provides the administration of communications between processes executing in disjoint address spaces on a local, or remote computer system.

In the TCS everything is viewed as either being a communication primitive, or, a communication point. The communication primitives are the low-level mechanisms used to provide the physical communication between various processes. The processes participating in the communication are referred to as communication points. Two or more communication points are connected by a communication link using the communication primitives.

The Communication Primitives

The communication primitives are built using the underlying computer operating system intraprocess and interprocess communication facilities and thus are operating-system-specific. On one operating system there may be, for example, five communication primitives supported, while another operating system may support twenty. A communication primitive generally must provide for several operations to be applied such as:

Create: The ability to create an instance of the primitive

Destroy: The ability to destroy an instance of the primitive

Send: The ability to send data to the primitive

Receive: The ability to receive data from the primitive

Cycle: Send a default and receive default messages to/from the primitive

Connect: Primitive specific connection function

Disconnect: Primitive specific disconnection function

Suspend: Primitive specific suspension function

Resume: Primitive specific resumption function

Communication primitives are registered with the Thread Communication Service for the specific operating system the TCS is executing on. The name, the location, and certain characteristics describing the communication primitive are retained by the TCS for subsequent use. In this context, the communication primitives become a reusable asset, needing to be developed and tested only one time.

Each communication primitive has a shared object, referred to as the communication primitive object, describing the location of the various operations to be applied when using this primitive type. All primitives have the same communication primitive object structure. The TCS will load the communication primitive object at runtime only when requested for use by a communication point.

In a sense, the communication primitive can be thought of as analogous to the physical connection of a telephone on a phone network. A twisted pair telephone would use one primitive while a cellular telephone would use a different primitive.

The Communication Points

A process can register zero or more communication points with the TCS. Each point is said to describe a service. Note, however, that a service can be a client of a different service, or a client of itself. The registration process notifies the TCS as to the name and location of the service, the default primitive to use for communicating to the service, and the default primitive to use when receiving messages from the service.

The registration process also identifies certain characteristics of the communication point. These characteristics include system-dependent information, implementation-dependent information, and usage-dependent information. The characteristics include:

Scope: Determines if service executes as a sibling thread, or in separate address space.

Stack: Required stack size

Idle: If service is to be idle on non-connects

Maxmsg: Maximum number of pending messages prior to suspension

Minmsg: Minimum number of pending messages at which service is resumed

Restart: Service is restartable

Termination: Method for terminating the service

Discarded: Method for discarding unwanted messages

The registered communication points are then retained by the TCS for subsequent use. When a communication point has been registered, a process can request to be connected to the service.

Using the telephone model example, a communication point is the equivalent of a destination telephone. That is, you can call an individual only by knowing the attributes describing that individual, such as a telephone number. The registered characteristics would be similar to your name and address being entered into the phone book. The TCS calls the TDS, if requested, to record the registered communication point in the TDS.

Connecting Communication Points

When a process is executing, it may request the TCS to connect it to a communication point. For the intraprocess communication version of the TCS, the service executes as a separate thread of control. In the interprocess communication version of the TCS, the service executes as a separate process.

There are several modifications permitted. First, when a communication point is registered, the registering process can identify the communication point as a public point. As such, only one instance of the service needs to be executing at any time. All processes requesting to use this point will share the same primitive. Alternatively, a service can be registered as a private service, in which case each process requesting communication to the service will be connected to their own instance of the service. Finally, when a service is initially registered, a maximum number of connection points can be preset. When this limit is reached, then all new processes requesting access to the service will be denied, until such time as the number of current instantiations of the service falls below the threshold.

A single process can be connected to multiple services simultaneously. This can be accomplished through a single connection, or, though multiple connections established by the process with the various services. In the former case, each time the process sends data, the data is actually sent to all services using the communication link. In the latter instance, only a single destination is connected to the communication link.

Again, using the telephone model as an example, this is equivalent to your calling a business associate on your telephone system. While connected, you can put the call on hold and dial another associate, or you can conference the associate in on the same call.

Mixing the Intraprocess and Interprocess Models

On systems supporting multiple threads of control within a single process address space, the TCS uses a special communication point called the intra.sub.--p communication point to execute commands on behalf of the TCS within that address space. That is to say, when the application process makes its initial request to the TCS, the intra.sub.--p communication point will bootstrap itself as a communication point within the application process address space. The TCS then issues specific commands to the intra.sub.--p communication point who executes these commands on behalf of the TCS. The use of the intra.sub.--p communication point is essential to permit intraprocess communication points while supporting interprocess communication points at the same time.

When an application makes a request to connect with a registered communication point, and that point must execute as a separate thread of control within the address space of the requesting process, then the TCS must have a method to satisfy the request. Since the TCS itself is executing in a different address space, it needs a worker thread executing within the requesting process's address space to spawn the requested communication point thread on its behalf.

The TCS also provides a method for a intraprocess communication point to be. treated as an interprocess communication point. When an application process makes a request to use an intraprocess communication point as an interprocess communication point, the TCS will execute a generic front end loader to initialize the address space of the new process, and then invokes the specific thread requested in that address space.

Communicating With a Service

Once connected, a process can send messages to a service. The primitive to send this message must accept the message, the size of the message, and the destination. Similarly, a process can request to receive a message from a service. In receiving the message, the process must identify the service it is to receive the message from, the maximum length of a message it can consume, and the actual size of the message returned.

Note that from the point of view of the application process, there is no need to be aware of the underlying physical primitive in use. Instead, the application sees that a Thread Communication Link is provided and need not deal with how it is provided.

Disconnecting From a Service

A process can request the TCS to disconnect it from a particular service. When this happens, the service can be terminate by the TCS if this was the only process connected to it. Otherwise, the service remains executing.

Using TCS for Remote Communication

In the TCS model, a special communication point can be created to monitor a communication device available to the computer system. This communication point acts as the conduit to send messages to, and receive messages from the communication device. The primitive used for this communication point wraps the identifier of the sending process, along with the identifier of the receiving process, around the message prior to sending the data out on the communication device. Similarly, when this communication point receives a message from the communication device, it unwraps the message to determine the process that the message is to be sent to. In this sense, the communication point is the conduit for communications with external systems.

The Broker Service

When a communication point is registered, the communication point may have a specific communication primitive required to either send or receive message. This poses a challenge for another communication point to connect if the requesting communication point requires a different communication primitive. When this happens, the TCS will search for a broker communication point which can convert the messages from the first primitive type to the second primitive type. The broker service, if necessary, will be inserted between the requesting communication point and the requested service communication point.

The TCS Model

In the TCS model, processes are nothing more than communication points. Application programs residing on a disk are also viewed as communication points (albeit the application program must be started for execution by the TCS). This powerful model enables application software development which may effectively commoditize software.

The Thread Directory Service

The Thread Directory Service is an extension of the Thread Communication Service offering persistence to the registered communication primitives and registered communication points. When a communication point is registered with the TDS, it is assigned a unique communication identifier. Numerous additional characteristics of the service can be registered within the TDS such as:

1. Textual description of the type of service

2. Sending communication primitive and receiving communication primitive

3. Communication mechanism used in establishing this service

4. Location of the service

5. Input types understood by the service

6. Output types generated by the service

7. Keyword search list used to locate this service entry

8. Token describing if the execution of the service can be started

9. Token describing the data representation in communication with the service, i.e. binary, ASCII, etc.

10. Token describing if the execution of the service must have previously been started

11. Token describing if Thread Communication Identifier is listed or unlisted

12. Token describing if a public connection to the service can be used

13. Token describing if a private connection to the service can be used

14. Token describing if a public connection is mandatory

15. Token describing if a private connection is mandatory

16. Token describing if the service is a component of a larger service

17. Shell actions to execute in initializing this service

18. The maximum number of concurrent communications

19. Licensing information

20. Other general user information

21. Link to additional Services required in using this service

22. Series of status information components including but not limited to security privileges and owner information.

23. Series of additional information components used for future enhancements

24. Thread Communication Identifier

25. Secondary Thread Service Directory

26. Usage Fee

27. Directory Service Fees

Of the foregoing, items 2 and 4 are essential; the others are optional, though desirable.

A process can request information from the Thread Directory Service specifying the desired search criteria. This is similar to dialing 411 and requesting a telephone number for an individual based on their name and street address. Each TDS has its own unique identifier. The registered communication points are assigned unique communication identifiers based on the TDS's identifier. Thus, communication points are fixed in the universe in this sense.

When the Thread Communication Service works in conjunction with the Thread Directory Service, all communication points to be connected are located via their communication identifiers.

When a connection is requested to a particular communication point, the requesting process specifies the unique communication identifier of the desired service. The TCS causes the identifier to be looked up in the TDS to determine how to connect to the service and then provides the actual connections.

The Thread Communication Switching Service

To minimize the message flow, a Thread Communication Switching Service is provided as a special instance of a communication point. It accepts multiple communication links redirecting the communications from one communication point to the appropriate destination communication point. As shown in FIGS. 1 to 4, a TCSS can communicate with communication points, or, to another TCSS.

Dynamic Configuration Management

Dynamic Configuration Management is a rule-based system for specifying components of software to use in constructing a Dynamically Configured Application Program. The components of software are loaded according to the specified rules and are subsequently executed.

The Application Process constructs the Dynamically Configured Application Program in the Dynamic Configuration Management (DCM) by specifying zero or more RULES identifying the components of the Dynamically Configured Application Program, the interactions between these components, the policy for evaluating these components, the order of evaluation of these components, and a method for satisfying the RULE. The Application Process can specify zero or more data files referred to as Virtual Program Rules Files containing RULES for the Dynamically Configured Application Program. In this sense, the Application Process provides the blueprint for constructing the Dynamically Configured Application Program.

The specification of a RULE includes the following information, although additional information may be incorporated by the implementation:

1. A unique alphanumeric name to identify the RULE

2. A DCM operator denoting the policy for evaluating the RULE

3. Zero or more Prerequisite RULES

4. Zero or more Attributes describing characteristics of the RULE

5. A method (possibly given as NULL) for satisfying the RULE

There are two classifications of RULES supported by the DCM given as Reserved Rules and Universal Rules. The Reserved Rules have special meaning to the DCM. The Universal Rules are specified by the Application Process. In either case, however, the Rules contain the minimum information described above.

A series of Reserved Rules, referred to as the Flow Rules, provide the framework for executing the Dynamically Configured Application Program. Whenever a Dynamically Configured Application Program is to be executed, the DCM begins by evaluating the Flow Rules. All other actions are derived as a result thereof. The Flow RULES include:

1. DCMINIT RULE

2. APINIT RULE

3. MAIN RULE

4. APDONE RULE

5. DCMDONE RULE

Note, however, that additional Flow Rules may be incorporated by the implementation.

A Dynamically Configured Application Program is therefore constructed by specifying Universal Rules as Prerequisites Rules of the Flow Rules. In evaluating a Flow Rule, the DCM will ensure that all Prerequisite Rules of the Flow Rule are evaluated first.

In evaluating a RULE, the DCM views the RULE name as the current rule. The evaluation process is such that the DCM will first evaluate all Prerequisite Rules of the current rule. Thus, a Prerequisite Rule becomes the current rule and the evaluation continues with its Prerequisite Rules.

When the current rule has no Prerequisite Rules listed, and the current rule has never been evaluated, then the DCM will execute the method for this rule. After executing the method for the current rule, the DCM attaches a time stamp value denoting when the current rule was evaluated.

When the current rule has one or more Prerequisite Rules, then the DCM compares the time stamp value of the current rule with that of its Prerequisite Rules. If the time stamp value of the current rule is older than the time stamp value of its Prerequisite Rules, then the current rule's method is executed to satisfy the rule and the time stamp value of the current rule is updated to denote when the current rule was evaluated. Otherwise, the current rule's time stamp value remains unchanged and the method is not executed.

After evaluating the last Flow Rule of the Dynamically Configured Application Program, the DCM considers the application as having completed and returns control back to the initial Application Process.

Initially when a RULE is specified, the DCM makes no assumptions as to what the RULE name represents. During the evaluation of the RULE, the DCM associates the RULE name with an entity understood by the DCM. This is called the binding process. The list of entities understood by the DCM and their corresponding interpretation by the DCM are provided during the initialization of the DCM. In this sense, the list of entities can be modified and updated over time based on market demand for new entities and their interpretations.

The binding of the RULE name to an entity understood by the DCM is determined by the RULE's attributes. In this sense, the Application Process can specify how the RULE is to be interpreted by the DCM.

Through the use of this method, Minor Services for an Application Service can be designed, implemented, tested, and distributed independently of the corresponding Application Program. The end-user can therefore purchase and install only those Minor Services of interest. When the Application Program is to be executed, the resulting Application Process will dynamically configure itself to provide the available Minor Services.

The advantage to the computer industry is that the Minor Services, for example, can be designed after the Application Program and sold individually to the end user. The implications are that:

1) the base Application Program need not be altered to support these additional Minor Services

2) since the end-user is purchasing only those Minor Services of interest, the end user does not have to provide additional media storage capacity to support unwanted Minor Services

3) additional Minor Services can be designed, implemented, tested, and installed after the base Application Program thus providing:

a) the designer of the Application Program the ability to design, implement, and test additional Minor Services based on new market demands without changing the existing base Application Program

b) the ability to design, implement, and test additional Minor Services specific to an individual customer without effecting other customers. In this sense, all customers would have the exact same base Application Program, but potentially different installed Minor Services

4) the development of additional Minor Services can be thoroughly tested as smaller units when compared to the approach used today in which a new, monolithic representation of the Application Program must be tested. The advantage herein is that the computational resources required to develop the software are decreased, the cost of testing is decreased, and the Minor Services can be delivered to the market in a shorter time interval.

The Configurable Application Program Service

The Configurable Application Program Service provides a method to dynamically reconfigure an application process. Through the CAPS, a communication point can be dynamically replaced by another communication point. This is important for real-time systems in which you would not want to terminate the application process to replace a defective module.

The Application Process uses the Configuration Administrator Minor Service to administer zero or more components of software from shared libraries. Each component is said to offer a Minor Service. The specifications for the administration of the Minor Services can be provided directly by the Application Service, or, indirectly through a data store monitored by the Configuration Administrator. These specifications can instruct the Configuration Administrator Minor Service to perform the desired operation immediately, at a predefined time (which may be an interval), or, as a result of some event which is later communicated to the Configuration Administrator Minor Service.

The Configuration Administrator Minor Service provides the following operations:

1. Locates specified Minor Services

2. Loads specified Minor Services

3. Executes specified Minor Services

4. Establishes communication channel with the specified Minor Service.

5. Suspends execution of specified Minor Services

6. Resumes execution of specified Minor Services

7. Replaces specified Minor Service with a new Minor Service rerouting communication channels as appropriate

8. Unloads specified Minor Service

9. Provides for manual state retention between replaceable Minor Services

10. Notification

Note that the Configuration Administrator Minor Service operations can be specified to occur at set time intervals; at predefined time periods; as a result of external events; or, as a result of internal events. Events, in this context are registered with the Configuration Administrator Minor Service to denote their occurrence.

The advantage is that an Application Program can be constructed and executed and subsequently reconfigured to take advantage of newly installed minor software services while the Application Process is executing. The implications of such a system are that:

1. Mission-critical Application Programs which require 24 hour, 365 days a year execution can be reconfigured without terminating execution of the existing Application Process.

2. An Application Process can be reconfigured without terminating that Application Process which would otherwise cause the Application Process to lose all data currently held in Random Access Memory

3. An Application Process which requires a significant initialization sequence does not need to be terminated to install new minor software services. Instead, the Application Process can be reconfigured on demand.

4. New software services can be designed, implemented, and tested using an existing Application Process such that the new services can be de-installed if found in fault without disrupting the existing Application Process.

5. Application Processes which monitor real-time events can be dynamically reconfigured to adjust to those real-time events without terminating the existing Application Process.

6. Diagnostic Minor Services can be configured into an existing Application Process for administrative, diagnostic, or statistical analysis and subsequently removed without affecting the existing Application Process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. Diagram showing Simple Thread Communication Link between TCP-1 and TCP-2.

FIG. 2. Diagram showing Two Thread Communication Links.

FIG. 3. Diagram showing Thread Communication Switch and Three Thread Communication Links.

FIG. 4. Diagram showing Thread Trunk Line.

FIG. 5. Diagram showing Example Dynamically Configured Application Program Rules.

FIG. 6. Diagram showing Example Application Process.

FIG. 7. Diagram showing Reconfiguring an Application Process.

FIG. 8. Diagram showing Active NEE Takes Input from NEEM, Output Read by Minor Service Reader Threads.

FIG. 9. Diagram showing Directed Communication Types between Communication Points

FIG. 10. Diagram showing Theoretical Open Systems Interconnection (OSI) Model.

FIG. 11. Pseudo Procedural Code for Example of Threaded State Machine.

FIGS. 12.A and 12.B State Machine Representation of Example of Threaded State Machine.

The following figures show exemplary source code in the C programming language, as implemented for Unix 4.2 MP TLP/5:

FIG. 13. Examples of Source Code for Binding Services.

FIG. 13.A Commands Used to Compile Binder Example.

FIG. 13.B Running Binding Service Example.

FIG. 13.C Sample Output from Binding Service

FIG. 13.D Simple Services.

FIG. 13.E Registering Binding Method and Binding Arbitrary Named Represenatives.

FIG. 13.F Header File Declaring Binding Method.

The following figures represent examples of data:

FIG. 13.G Examples of Pattern, Transformation, Locate, Status and Query for a Shared Object in a Shared Library.

FIG. 13.H Example of Shared Library Binding Method.

FIG. 13.I Example of Shared Library Binding Method including Pattern, Transformation, Locate, Status & Query.

FIG. 13.J Example of Data Structures Header File.

FIG. 13.K Example of Registering a Binding Service Method to Make Such Method Available to Binding Services (BSV).

FIG. 14. Samples of Particular Services.

FIG. 14.A Sample Communication Points Module.

FIG. 14.B Sample Output for Broker Data.

FIG. 14.C Sample Output for Weather Data.

The following figures show exemplary source code:

FIG. 15. Examples of Communications Modules.

FIG. 15.A Communication Data Header File.

FIG. 15.B Communication Data Module.

FIG. 16. Compoints.

FIG. 16.A Compoints Header File.

FIG. 16.B Compoints Module.

FIG. 17. Communications Registration.

FIG. 17.A Communications Registration Header File.

FIG. 17.B Communications Registration Module.

FIG. 17.C Communications Point Header File.

FIG. 17.D Communications Point Module.

FIG. 18. Thread Condition Variables.

FIG. 18.A Thread Condition Variable Header File.

FIG. 18.B Thread Condition Variable Module.

FIG. 19. Generic Compoints.

FIG. 19.A Generic Compoint Header File.

FIG. 19.B Generic Compoint Module.

FIG. 20. Thread Link Lists.

FIG. 20.A Thread Link List Header File.

FIG. 20.B Thread Link List Module.

FIG. 21. Mutex Thread Log.

FIG. 21.A Mutex Thread Log Header File.

FIG. 21.B Mutex Thread Log Module.

FIG. 22. Thread Mutex.

FIG. 22.A Thread Mutex Header File.

FIG. 22.B Thread Mutex Module.

FIG. 23. Communication Primitives.

FIG. 23.A Communication Primitive Header File.

FIG. 23.B Communication Primitive Module.

FIG. 23.C Communication Primitive Data Header File.

FIG. 23.D Communication Primitive Data Module.

FIG. 24. Thread Queue Conditions

FIG. 24.A Thread Queue Condition Header File.

FIG. 24.B Thread Queue Condition Module.

FIG. 25. Registry.

FIG. 25.A Registry Header File.

FIG. 25.B Registry Module.

FIG. 26. Minor Services Communication.

FIG. 26.A Minor Services Communication Module.

FIG. 27. Thread Reader-Writer.

FIG. 27.A Thread Reader-Writer Lock Header File.

FIG. 27.B Thread Reader-Writer Lock Module.

DETAILED DESCRIPTION OF THE INVENTION

The various aspects of the present invention can be implemented on a digital computer running an operating system that supports runtime-loadable software modules, such as Unix SVR4.2 MP TLP/5 (Unix System Laboratories, a subsidiary of Novell Corporation). Such a computer may, for example, be a Gateway 2000 computer having an Intel 486 microprocessor, or any other hardware compatible with that operating system. Many other operating systems may alternatively be used, including SunSoft Solaris 2.X, Microsoft Windows 95, Microsoft Windows NT, IBM's AIX, and Hewlett-Packard HP-UX, on any hardware compatible therewith. See, e.g. Solaris 2.2, SunOS 5.2 Reference Manual, Section 3, Library Routines (A-M) and (N-Z)(SunSoft Part No. 801-3954-10, Revision A, May 1993).

Configurable Application Program Service

The term Application Program is used to describe a software application residing on a medium accessible to the computer system.

An Application Process is said to provide some well-known service, e.g. wordprocessing, spreadsheet, graphics, etc. The Application Program may be devised to provide a series of one or more Minor Services and a Primary Service, which collectively constitute the Application Service.

The term Application Process, as used in this document, refers to the overall computer representation of the Application Program's execution. In this definition, the term Application Process is defined to incorporate all processes of various "weight" including, but not limited to, heavy weight, medium weight, and light weight processes relating to the Application Service. A heavy-weight process executes in its own address space, whereas medium-weight and light-weight processes may execute within the same address space. The Application Process may constitute one or more of these processes. Each of these processes is said to have a Thread of execution.

A Thread, in this context, represents an execution stream of the Application Process. The notion of a Thread can be provided by the underlying operating system, referred to as kernel-supported threads, or can be provided at the application level, referred to as user-level threads, or can be a mixture of the two. For the purposes of this description, these will collectively be referred to as Threads. Note that in a distributed environment, one or more of these Threads may be executing on a remote computer system.

The Application Process may be confined locally to the computer system on which the Application Process was initially started, or may have its execution threads distributed among various computer systems accessible to the computer system on which the Application Process was initially started.

When a user of the computer system requests to execute an Application Program, the Application Program is loaded into the computer's memory having a single Thread of execution. This initial Thread may then create additional Threads on the local computer system, or possibly on a remote computer system.

The creation of a new Thread requires the Application Process to specify the starting point of the new Thread. In procedural computer languages, for example, this would require the requesting Thread to specify the address of the procedure to begin as a new Thread. On some implementations, the new Thread must be identified by its Application Program name. The implication herein is that the Application Program is created (i.e. compiled) with this information present.

The Application Program is therefore a static representation of a well-known functionality and is not easily able to dynamically load additional Threads unknown at the time the Application Program was developed. There are, however, certain Applications Programs which provide a listing of installed computer Application Programs either through a textual display or through a graphical representation referred to as an icon. Additionally, certain Application Processes search specific directories for available Application Programs to execute as Application Co-Processes, but again, the criteria for their representation is static and unalterable by the end user.

In the textual representation, the name of the Application Program is provided with zero or more additional information components such as the owner, the size, and/or execution privileges. This listing is shown to the user, who may then enter the name of the application to execute.

Alternatively, when using a graphical user interface with an Icon, the name of the Application Program, its specific location on the computer system, and other information is required to execute the Thread. A further limitation of the Icon is that one Application Process can be started by selecting the Icon, but that Application Process cannot select a new Icon to execute as an Application Co-Process. That is to say, the Icon is a graphical representation for the end user to select.

A limitation of both the textual and graphical representation of the available Application Programs is that the information displayed to the user is dependent on the underlying operating system implementation. Certain operating systems will display the name, the size in bytes, the owner, the date created, and execution mode while others will display a subset of this information and possibly other system-dependent information. Regardless, however, the user cannot easily associate additional information with the installed application in a useful manner. Finally, many users have manually created what has become known as README files to describe this information.

There are many instances in which an Application Process will select different Minor Services depending on installed features, additional software available to the computer system, or due to other factors external to the Application Process itself. Currently, the only provisions to support such run-time changes to the Application Process are to design the Application Program with the appropriate logic.

This disadvantage to this approach, however, is that it limits the ability of the Application Process to dynamically configure itself based on available Minor Services, or due to other factors external to the Application Process itself. Additionally, the Application Process cannot appropriately handle cases in which an available Minor Service may conflict with another Minor Service. Once the incompatibility is detected, the Application Process will simply print an error message and terminate its processing.

Finally, an Application Process which locates available Minor Services has no simple provision for executing these Minor Services, communicating with these Minor Services, nor ensuring a proper ordering of the execution of these Minor Services.

The prior art therefore does not provide the necessary mechanisms for an Application Process to dynamically alter its execution based on Minor Services available either locally or remotely to the computer system. Additionally, the prior art does not provide the necessary mechanisms for the same Application Program to behave differently on two separate computer system offering two very different sets of Minor Services without this logic being introduced into the Application Program from the onset.

The prior art also does not provide the mechanisms for resolving feature conflicts in which there are two or more installed Minor Services available to the Application Process, but whose use are mutually exclusive. The Application Program will typically be designed to execute the first feature ("Feature A"), and then the second ("Feature B"). If Feature B conflicts with the use of Feature A, there are no simple remedies to support a resolution. Consider, for example, that the Application Process performs various initialization sequences required for Feature A. The Application Process may then also execute various initialization sequences for Feature B. During the initialization sequences for Feature A, certain values may be set in the Application Process which are inappropriate in the case of Feature B being present.

Within the prior art there are various approaches for configuration of Application Programs. Typically referred to as Software Construction Utilities, these approaches provide a rule-based system describing how an Application Program should be constructed from its corresponding application programming language source code. Examples of Software Construction Utilities include:

1. augmented make--"Augmented Version of Make," UNIX System V, Release 2.0 Support Tools Guide, pp: 3.1-19, April 1984.

2. build--Erickson, B., Pellegron, J. F., "Build--A Software Construction Tool," AT&T Bell Laboratories Technical Journal, vol. 63, No. 6, Part 2, pp: 1049-1059, July 1984.

3. make--Feldman, S., "Make--A Program for Maintaining Computer Programs," Software--Practice and Experience, vol. 9, No. 4, pp: 256-265, April 1979.

4. mk--Hume, A., "Mk: A Successor To Make," USENIX Phoenix 1987 Summer Conference Proceedings, pp: 445-457, 1987.

5. nmake--Fowler, G. S., "The Fourth Generation Make," USENIX Portland 1985 Summer Conference Proceedings, pp: 159-174, 1985.

6. Microsoft NMAKE--"Microsoft C: Advances Programming Techniques," Microsoft Corporation, pp: 103-132, 1990.

Here, the source code provides the necessary algorithm, logic, and instructions in a human-readable form. This source code must then be compiled into an Application Program which the computer can then load and execute. The process of determining the necessary actions to create the Application Program are typically controlled by a software construction Application Program (a "make" utility) which reads specifications from a data file known as a "makefile". This process is well known and well understood in the computer programming profession. The makefile contains specification of the form:

target.sub.--name:prerequisite.sub.--list

ACTION

to denote that a target is dependent on prerequisites. If one or more of the prerequisites is newer than the target, then the ACTION is performed to construct the target. Each prerequisite can be listed as a target of another rule. As an example, consider:

rule 1 A:B C

concatenate B and C to construct A

rule 2 B:b

copy "b" to "B"

rule 3 C:c

copy "c" to "C"

In this example, the rule to construct the target "A" shows it has a dependency on prerequisites "B" and "C". Note, however, that "B" is dependent on "b" according to the second rule, and that "C" is dependent on "c" based on rule 3. If "c" has changed since the last time "C" was constructed, then the ACTION for rule 3 would be performed to reconstruct C. Similarly, if "b" has changed since the last time "B" was constructed, then the ACTION for rule 2 would be performed to reconstruct B. Note that the ACTION for rule 2 and the ACTION for rule 3 could in fact occur simultaneously since there are no other dependencies on these rules. After rule 2 and rule 3 has completed, then rule 1 can continue. Here, if "B" or "C" has changed since the last time "A" has been constructed, then the ACTION for rule 1 will be performed to reconstruct A.

The issue of software configuration has. historically been addressed by one of the following mechanisms:

1. All of the Application Program's Minor Services are developed and compiled into the Application Program which is then sold to the customer. I shall refer to this "Non-featuring Software."

2. All of the Application Program's Minor Services are developed and compiled into the Application Program which is then sold to the customer. Certain Minor Services, however, will be inaccessible to the customer unless the customer pays additional fees. At that time, a key file is provided to the customer with the appropriate purchased Minor Services turned on. I shall refer to this as "Run-Time Featuring."

3. All of the Application Program's Minor Services are developed, but during the software construction process certain features will be selected to include in the Application Program. I shall refer to this as "Compile-Time Featuring."

4. All of the Application Program's Minor Services are developed, but sold as separate Application Programs. In this instance, all of the components representing the Application are well known. During the execution of the Application Program, the features are tested to see if they are present. If a feature is not present, then it is simply ignored. I shall refer to this as "Load-Time Featuring."

Application Programs are typically designed and distributed following the Non-featuring Software model. Consider, for example, that when purchasing a Word Processing Application you receive all of the latest features available. This has the disadvantage that you are paying for features which you may not need.

With "Run-Time Featuring", the Application Program consists of the monolithic representation of the application. Thus you receive a potentially large Application Program with certain portions of the Application Program inaccessible to you.

Nonetheless, you receive the largest possible representation. The disadvantage to this approach is that you cannot ship the product until all features have been developed. Additionally, the customer must have enough memory and storage capacity for the entire Application Program even though only a one Minor Service may have been purchased.

With Compile-Time Featuring, the source code representing the application has numerous sections delineated with conditional inclusions based on specified criteria. As an example, in the C language it is customary to use:

                    #if defined(FEATURE.sub.-- A)
                          . . .
                         #elif defined(FEATURE.sub.-- B)
                          . . .
                         #endif

                             TABLE 1
             Binding Method Registration Information.
                      Order of Evaluation
                      Location of Binding Method
                      Name of Binding Method

                             TABLE 2
                     Default Binding Methods.
        File Binding Method
                      a method to bind the arbitrary named
                      representation to a file accessible by the
                      computer system
        Shell Binding Method
                      a method to bind the arbitrary named
                      representation to a user level shell
        Data Binding Method
                      a method to bind the arbitrary named
                      representation to a datum available to the
                      Application Process
        Function Binding Method
                      a method to bind the arbitrary named
                      representation to a function (procedure)
                      accessible to the Application Process
        Thread Binding Method
                      a method to bind the arbitrary named
                      representation to a thread of the Application
                      Process
        Process Binding Method
                      a method to bind the arbitrary named
                      representation to an existing Application
                      Process

                             TABLE 3
                    Binding Method Operations
                         Pattern Matching Method
                         Name Transformation Method
                         Locate Method
                         Status Method
                         Query Method

                             TABLE 4
                  Rule Specification Components
        A unique alphanumeric name to identify the RULE
        A DCM operator denoting the policy for evaluating the RULE
        Zero or more Prerequisite Universal RULES
        Zero or more Attributes describing characteristics of the RULE
        A method (possibly given as NULL) for satisfying the RULE

                             TABLE 5
                         The Flow Rules.
                             DCMINIT RULE
                             APINIT RULE
                             MAIN RULE
                             DONE RULE
                             APDONE RULE
                             DCMDONE RULE