Method and apparatus for navigation of relational databases on distributed networks6038566Abstract Relational databases are browsed in a manner that mirrors the interactive browsing of world wide web pages. A schema-based navigational layer is used on top of conventional physical, logical and conceptual database schema layers, to dynamically map data stored in a relational database onto web pages. The navigational schema or schema base is an independent abstraction from the underlying conceptual database schema. The schema base is constructed from relationships and information models. The schema base can be reused or derived from the database design process or produced specifically for navigation through the database. An object-role schema base is used to demonstrate the traversal of relational information in a regenerative, propagative manner. Navigating a database via the presented schema extends the conventional database concept of the logical view to an interactive model of logical view-transitions. The technique is a simple and powerful model for automated access to relational databases making available vast amounts of data stored in relational databases for Internet and intranet web browsing. Claims What is claimed is: Description BACKGROUND
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Object 1 (painting, Mona Lisa) --- relation
(is on display at/contains) --- Object 2 (museum, Louvre)
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Therefore, assume that a page entitled the "Mona Lisa" is accessed by a server computer. The page is expected to provide information focused on the painting "The Mona Lisa." This information may include facts that Leonardo Da Vinci painted it and thus the words "Leonardo Da Vinci" may be hotlinked to a page focused on him. Correspondence, therefore, exists between the information on the page Mona Lisa and other information underlying it. Viewing pages as conceptual objects can have the information represented on the page as page links to other related objects. This begins to associate browsing web pages and browsing conceptual objects. The next step is to specify how an underlying data representation maps to conceptual information objects and to browsable web pages. Conceptual objects are implemented as programs and the schema base that act dynamically to provide content. Pure object databases eliminate impediments to translating real world object models into an implemented database. Although relational databases do not satisfy the object model, nevertheless, they are well-established, standardized and extensively used on the world wide web. Referring now to FIGS. 3-5, the contents of both web pages and objects can be viewed as being intrinsic, that is, owned by the web pages or objects, or extrinsic, that is, referenced by the web page or to another object. As shown, the intrinsic contents "John Smith" 32 and "age 20" 34 are displayed on the page 31. That is, an object can contain information by either value or reference. In addition, its extrinsic contents 38 are also displayed on the page 31 as a reference, hotlink or hyperlink 38 "Best Friends page." An object can contain information either by value or by reference. Thus, for example, viewing the web page 31 (FIG. 3) as a programming object 40 (FIG. 4) shows the object 40 containing all of the intrinsic information displayed on the page 30 (FIG. 3), that is, "John Smith" 42 and "age 20" 44 as well as extrinsic information corresponding to hyperlink 38 (FIG. 3) expressed as a relation 48. The object 40 is connected to a referenced object 49 "Frank" by relationship "friend" 48. The information on the web page can also be represented 51 as a data object 50 (FIG. 5) linked by a link 58 to a page "Frank" 59. As shown in FIG. 6, extrinsic information can be retrieved via relations to other owning objects. Thus, the information specified by a link between two objects can be retrieved as a relational query. Thus, the relational query 62 in the relationship table "entity" 60 can retrieve information specified by the link between the objects "John" and "Frank." The link can be viewed as a relational query such as: select "Best.sub.-- Friend from BF where person=`John`." The result or satisfaction of the relational query is represented by the linked data object 51 as was shown in FIG. 5. Referring now to FIG. 7, relational data in a relational database 70 is presented as a set of logical views 72. In particular, the entities 70a which represent information in tables in a relational database can be extracted into logical sets 72a of information represented by the logical view 72. The logical sets 72a of information are the result of a query of the relational database using the relational entities in the database and relationships between the entities. Each of the logical views 72 can represent extrinsic or intrinsic information for a conceptual object as illustrated for the conceptual object view 74. Any conceptual objects data can be formed from a collection of queries to the underlying database. Thus, as shown in FIG. 7, the object 1 intrinsic data can correspond to the entity 1, whereas the selection criteria for its extrinsic data in the logical view can be represented by the relationships R12, R21 and R13, R31. As in the logical view of the relational database, the object conceptual view shows (as in the object role model) the relationships between "object 1" and "object 2" and "object 1" and "object 3." These relationships are R12, R21 and R13, R31, respectively. The objects are modeled as units that have distinct properties in relationship to other objects. The object is defined by its intrinsically possessive properties as well as by its connections to other objects. A web page, on the other hand, is a composite of material formed from sources distributed over a network. The web page generally has one main page with embedded links and resources. Here the intrinsic information for the conceptual object corresponds to a browsable web page, whereas, relationships between objects correspond to the links on the web. The links on the web page, therefore, can trigger a new set of queries concerning the data represented by the relational database. Browsing on the web relies upon the ability to navigate, that is, move from one page to another page among a set of pages. Navigational moves are determined by the embedded links on a particular page. Therefore, moving from one page to another is a request for content as satisfied by the underlying relational database. The hyperlinks can be regenerative links, that is, they dynamically hook back into the database based upon a conceptual object module or a schema base 30 (FIG. 22) that overlies the database. Each information state is a snapshot of information in the database. The action of browsing is the combination of visiting pages and following links between the pages. This sequence of states and transitions can be mapped to sequences of logical view states and transitions to other view states. Displaying of individual states of information is the result of a collection of query/logical views. The relation model, likewise, defines transitions between information states. A relation is specified in relational database theory by relational algebra or in practice by a structured query language (SQL). The inherent structure of information formed as a relational model can be used to provide traversable links during the act of browsing web pages. Referring now to FIG. 8, a technique 80 for generating schemas based upon a design of a database 19 is illustrated. The technique involves reverse engineering of an analysis 82, design 83 and implementation 84 of a database 19 to produce a schema base 30. That is, FIG. 8 shows a possible approach between database design information and its use in developing a schema for use with a navigator 24 for implemented databases. This is one way to leverage design data in the production of a schema base 30. The schema base 30 can also be constructed without such a process and irrespective of any design data, as done in the example to follow. A simplified object-role representation permits the use of object-role design tools that reverse engineer object-role base constructs. The schema 30 is used with a navigator 24 to interface the database 19 to a web page display (browser). A well-known object role model is suitable for implementing a schema database 30. The object role model embodies similar concepts with object oriented models of programming and as used herein the term "object role" refers to a general use of the term object and role as a relationship between objects. Objects are viewed as belonging to a particular class. The navigational program that operates on schema base 30 will find all relationship/roles that a particular class can possess and once the program 24 finds such relationships, it will fill in each of these classes with particular instances of the class. In addition, if the classes in the binary relation are the same, then a recursive retrieval can be supported in the schema. For example, the self-referencing rule:
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schema(Part, Part, subpart of, `Select part.name
where name = part.subpart and name=%s`)
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can be used to traverse recursive data including grammar specifications.
TABLE 1
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Part Subpart
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Pedestal Base
Pedestal Dado
Pedestal Cap
Column Column Base
Column Shaft
Column Capital
Entablature Architrave
Entablature Frieze
Entablature Cornice
Capital Necking
Capital echinus
Capital Abacus
Base plinth
Abacus cymation
Abacus fillet
Necking cincture
Necking astragal
Necking fillets
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Thus, recursiveness is shown where a part such as "pedestal" is defined in terms of other parts such as "base", "dado" and "cap." The part "base" is in turn defined by "plinth." Browsing this information would resolve to instantiating the next subpart of an instance of class(Part). The results can be shown textually or graphically. In addition, multiple, distinct or connected schemas can co-exist. Thus, each rule in a schema base can be identified by a category and/or an owner's schema: schema{class 1, class 2, relation 12, extraction, owner} In addition, this approach can support multiple, separate or combined pathways. A set of schemas can be chosen as well as rules to choose the schemas can be provided to customize navigational pathways. The schema base 30 specifies how each page is hotlinked to access a next logical retrieval of information. Each page object is viewed as one state of retrieved information. Inherent connections between objects, i.e, "roles" between objects specify a logical relationship between the objects. The schema base 30 not only specifies what information should be retrieved to represent information about the object, but it also specifies what relations or roles to other objects can follow. These relations or roles are translated into hotlinks that appear on web pages. The relational database navigator model will now be described with respect to FIGS. 9-23. As an illustrative example, information regarding hospitals is presumed to reside in a local database and/or in a relational database on a remote database server. Techniques for developing a schema base 30 to represent the information in the relational database and to interface that information to a web browser will be described. This example will demonstrate how an object-role schema base maps relational data from a relational database onto web pages and how it draws its information from the relational database. The database is navigated, that is, browsed with each page's contents and links as they are generated. The schema base 30 is independent of the underlying database. The schema base 30 is provided as a level on top of the physical and logical levels of the database. Therefore, the underlying relational data models do not have to be unified. The schema base 30 (FIG. 22) is built and interposed between the relational database and a web browser. The schema base 30 maps the act of browsing web pages to querying a database. The schema base 30 is a collection of objects and relationships between the objects. The schema base 30 could specify some or all permitted states and transitions of the conceptual database. Relational database metadata information resides in system tables and is often referred to as "conceptual schema." Conceptual schema is distinguished from the described schema base 30. A "schema base" refers to meta information about all conceptual objects, relationships between objects and extraction of information to satisfy requests for this information from an underlying relational database. The schema base 30 includes a set of schema rules, the schema rules having the form:
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schema rule: {class 1, class 2, relation 12, extraction,
propagation}
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An example of a schema rule using a hospital information database would be:
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Doctor, patient, treated, `Select Patient from patientTreatment
where Doctor=%s`;
Doctor, Hospital, practices, `Select Hospital from Doctors where
Doctor=%s`, propagate (Patient);
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Referring now to FIG. 9, an illustration of a relational database includes various tables storing information in fields. In particular, the table 100 "hospital" has fields "name", "address", "phone." Additional tables are also provided such as, for example, patient 110, doctor 120 and so forth. These tables along with their respective relationships are used in development of a schema to define conceptual objects for the schema base 30 (FIG. 22). Thus, the table "hospital" 100 and table "Patient" 110 and a table "Patient Visit" 130 along with their respective relationships are used to define the role 102 "Patient-Visited-Hospital" for the conceptual object "patient" and the conceptual object "hospital", for example. A second role 112 for "patient" as a conceptual object is shown for example by the role "Patient-suffered from-Illness" which involves other tables and relationships. The relationships between the various tables are classified as a relation type. Thus, between the tables "patient visit" 130 and "patient" 120 there is a many to one relationship denoted as N:1; whereas, between the table "hospital" 100 and "patient visit" 130 there is a one to many relationship denoted as 1:N. The relationships between the hospital table 100 and the patient table 110 can be used to construct roles, as shown in FIG. 10. Thus, for example, one illustrated role set 104 "visited"/"is visited by" involves tables patient 110 and hospital 100. This is a duality in that for the statement "object 1-role-object 2" this provides the role 104a "patient visited hospital" when hospital is the referenced object or the role 104b "hospital visited by patient" when patient is the referenced object. Additional roles are shown in FIG. 10. Referring now to FIG. 11, as an illustrative example browsing through a relational database 19 called "hospitals" will be described. The relational database 19 is on a remote server. Initially, in this example, a starting web page "hospitals" is shown. Here three hospitals are listed, "University Hospital", "Kids Hospital" and "Saint Hope Hospital." Each of these are hyperlinks that dynamically form a page for the respective hospital. Here the initial page (FIG. 11) is a static page having no information other than hyperlinks to other pages. Selecting one of these hyperlinks invokes a request or query to find information about the class "hospital" for the particular object or instance selected. Thus, for example, selecting "Kids Hospital" is a request to find information about the class "hospital" and the particular object "Kids Hospital." Selecting "Kids Hospital", selects a hyperlink to the "Kids Hospital" page as illustrated in FIG. 12. Referring now to FIG. 12, the "Kids Hospital" page includes information, for example, the names of the patients "visited by" the Kids Hospital. There are five names of persons "visited by" the "Kids Hospital." The new page Kids Hospital is dynamically produced by finding relations "visited by" between the class hospital, in this instance, Kids Hospital, and other objects in the database. In this case, the Kids Hospital was "visited by" the list of people. The schema base for this page is shown in FIG. 13 with the object 100' and the object 110' linked by relationship 104b'. The objects 1001 and 110' correspond to the information in tables 100, 110 and 130 (FIG. 9) and are hyperlinked 104b' via the relationship "visited by" 104b (FIG. 10). Parenthetically, if a patient page is accessed the relationship "visited" would link the instance of the class "patient" to the instance of the class "hospital." This will be further illustrated in conjunction with FIG. 16. Referring now to FIG. 14, a second example is shown. The class "hospital" instance "Saint Hope Hospital", as illustrated in FIG. 11, is selected. Retrieval provides information which is found on a dynamically generated Saint Hope Hospital page, as illustrated in FIG. 14. The retrieval finds that the hospital "Saint Hope" is located on a location map. This example shows that two objects of the class "hospital" can retrieve different types of information based on the availability of the information. This use of a location map illustrates the use of multi-media complex data types such as images and maps. The underlying schema base for the page "Saint Hope Hospital" is shown in FIG. 15 where the hospital object 100' has a relationship 106' "is located at" to an object "place" 150' which has a relationship to a "map" via the relationship "is shown on." The object "hospital" 100' instance "Saint Hope", has a relationship to the object "patient" 110' via the relation "is visited by" 104b' producing the instance "John Kelly." Thus, this example using the "Saint Hope Hospital" produces for the class hospital instance Saint Hope two types of information, the patients who visited the hospital and the location of the hospital. Whereas, for the "Kids Hospital" the information regarding location was not available on the "Kids Hospital" page. Referring now to FIG. 16, a page "Andy Green" is illustrated. This page is accessed by activating a hyperlink "Andy Green." This hyperlink "Andy Green" is illustrated on the "Kids Hospital" page (FIG. 12). The Andy Green page shows three pieces of information concerning "Andy Green", the "visited" hospital, the conditions "suffered from", here bronchiolitis and the treating physician, "Dr. Joanne Katz." As can be seen in this example, by selecting Andy Green from the Kids Hospital, a return-type linking is provided in which the visited hospital (Kids Hospital) now becomes a link in the "Andy Green" page. This is a link back to the "Kids Hospital" page. The schema diagram which implements the Andy Green page is shown in FIG. 17. It includes the class patient 110' with the relationship "visited" 104a' linking to the class "hospital" 100'. This particular linking is the return linking of that shown in conjunction with FIG. 13. Additional linkings are also provided for other information on the page, thus, the class "patient" 110' is linked from a relation "suffered from" 107a' to an object "illness" 140' and the object "patient" 110' is linked by a relationship "treated by" 109b' to a "doctor" 120'. The object "date" 160' is linked via the "on" relationship 109c' and the "on" relationship 107c'. This schema shows that the relationship between objects "doctor" and "illness" and objects "patient" and "illness" are both tertiary relationships that include a date. This example can be explicitly extended to handle any number of relationships. From the hyperlink "Dr. Joanne Katz", a "Dr. Joanne Katz" page is dynamically produced retrieving information on Dr. Joanne Katz as shown in FIG. 18. The "Dr. Joanne Katz" page shows a list of "patients" "treated", the "diagnosis made", the "hospital" she practices at and a map of where the hospital is. The schema that produces this page is illustrated in conjunction with FIG. 19. This shows that the object "doctor" 120' is hyperlinked via the relationship "practices at" 124a' to the object hospital 100'. Similarly, the object doctor 120' is linked via the relationship "treats" 109a' to the object "patient" 110'. In addition, relations 121a' and 122a' link the object "doctor" 120' to the object "illness" 140' and "place" 150'. Using the "Dr. Joanne Katz" page and clicking on one of the diagnoses made by Dr. Katz such as the "bronchiolitis" diagnosis will produce a "bronchiolitis page" which displays information about the illness "bronchiolitis." In the illustrated example, the illness bronchiolitis shows cases of it being recorded and general information about the illness. A more elaborate implementation could easily retrieve listings in medical literature, statistics and so forth about this disease. The bronchiolitis information displayed includes patients who suffer from the disease such as "Andy Green" and two instances of John Kelly. Clicking on Andy Green or John Kelly will navigate back to the Andy Green or a John Kelly patient page. The schema which provides the page of FIG. 20 is illustrated in conjunction with FIG. 21 includes the object illness 140' which maps to object "illness symptoms" 180' and "patient" 120' via relationships "has symptoms" and "was suffered by" 142a' and 144a', respectively. Referring now to FIG. 22, the complete schema used in the example of FIGS. 9-21 is shown. The complete schema includes the objects "hospital" 100', "patient" 110', "doctor" 120', "illness" 140', "place" 150', and "illness symptoms" 180' as well as relationships between these objects to provide the requisite hyperlinks. A general format for a data structure representing relations between objects is shown in Table 2.
TABLE 2
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FORMAT:
Objectl;Object2;Role;extractorType;extractorcode;owner;nu
mberOfSubstitutions;Substitutions;PropagateOnAnswerColumn
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As shown above in TABLE 2, the fields "Object1" and "Object2" are respectively the referencing and referenced objects of a relation. The field "Role" is the relation between the referencing and referenced object. The field "extractorType" is an identifier of the type of query, e.g., text based or SQL. The "extractorCode" is the code used to execute the query type to retrieve information from the database. The "owner" is a field which is used to identify the owner of the entry. The owner field permits various schemas to co-exist using common relational or text databases. The field "numberofsubstitutions" is the execution parameter that is used. The field "PropagagesOnAnswerColumn" is the column in the database where the parameter is found. Specific examples for the data structure for each of the object-object relationships is shown in Table 3.
TABLE 3
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Hospital;Doctor;Staffedby;sql;select name from Doctor
where hospital="%s";me;1,O1;1;
Patient;Hospital;Visited Hospital;sql;select hospital+
"("+fromdate+"-"+todate+")", hospital from patient visit
where patient="%s";me;1;O1;2;
Patient;Illness;Suffered from;sql;select
Illness+"on"+TreatmentDate, Doctor from PatientTreatment
where Patient="%s";me;1;O1;2;
Doctor;patient;Treated;sql;select Patient from
PatientTreatment where doctor="%s";me;1;O1;1;
Doctor;Illness;DiagnosesMade;sql;selecctIllness.name+"("+
Illness.Description+")", Illness.name from Illness,
PatientTreatment where
PatientTreatment.illness=illness.name and
Doctor="%s";me;1;O1;2;
Doctor;Hospital;Practices Medicine At;sql;select Hospital
from doctor where Name="%s";me;1;O1;1;
Illness;Patient;suffered by Patient;sql;select Patient
from PatientTreatment where Illness="%s";me;1;O1;1;
Illness;IllnessInfo;General Information;sql;select Info
from IllnessInfo where Illness-"%s";me;1;O1;0;
Hospital;Location;is located at;sql;select "<img
src="+URL+"><p>Directions: "+Directions from Location
where Place="%s";me;1;O1;0;
Doctor;Location;is located at;sql;select "<img
src="+URL+"><p>Directions: "+Directions from Location
where Place="%s";me;1;O1;0;
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Having described preferred embodiments of the invention, other embodiments incorporating its concept may be used. It is felt, therefore, that this invention should not be limited to the disclosed embodiment, but rather should be limited only by the spirit and scope of the appended claims.
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