Method and apparatus for tracking and viewing changes on the web

Abstract

A system for accessing documents contained in a remote repository, which change in content from version-to-version. The system allows users to specify lists of documents of interest. Based on the lists, the system maintains an archive, which contains a copy of one version of each listed document, and material from which the other versions can be reconstructed. The system periodically compares the archive with current versions of the documents located in the repository, and updates the archive, thereby maintaining the ability to reconstruct current versions. The system also monitors access to the versions by each user. When a user calls for a current version, the system presents the current version, and indicates what parts of the current version have not been previously accessed by the user.

Claims

We claim:

1. A method for monitoring changes in a document stored on the World Wide Web, comprising the steps of:

copying an original document selected by a user from the World Wide Web to create a copied document on a server separate from the World Wide Web and under independent control;

monitoring for changes in the original document;

archiving, on the separate server, the changes in the original document, as detected during such monitoring;

storing various versions of the original document on the separate server;

presenting to the user, in response to a request to access the original document, a current version of the original document as archived, and an option to compare selected versions, as archived.

2. A method according to claim 1 further comprising the step of:

presenting to the user, an option to view a history of different versions of the original document.

3. A method according to claim 1 further comprising the step of:

recording the times when the user accesses each document.

4. A method according to claim 1, further comprising the steps of:

comparing the current version of the original document as archived with the copied document.

5. A method according to claim 1 further comprising the step of:

notifying the user, the changes in the original selected document since the user last accessed the document.

6. A method according to claim 5 wherein the user is notified upon a specific request by the user.

7. A method according to claim 5 wherein the user is notified simply by the user's access to the selected document.

8. A method according to claim 5 wherein the user is notified by electronic mail message.

9. A method according to claim 4 wherein the documents that are compared for any changes are determined by default.

10. A method according to claim 4 wherein the documents that are compared for any changes are specified by the user.

Description

REFERENCE TO A MICROFICHE APPENDIX

Included with and forming part of this specification is a microfiche appendix, including 1 sheet having a total of 52 frames.

The invention concerns presentation of a current version of a document retrieved from a data repository. The presentation indicates changes made in the document since the viewer accessed a previous version.

BACKGROUND OF THE INVENTION

Information which is stored in computerized systems can change frequently, and without notice. As an example, software under development frequently involves many persons, and is commonly stored at a central location. Each person can change the software on an ad hoc basis, without knowledge of others.

In such systems containing changeable data, a person who examines information on a given day does not, in general, know whether, and how, the information has changed since a previous examination. Consequently, the person must spend time comparing currently available information with previous versions of the information.

Software exists for facilitating this comparison. For example, systems known as "version control systems," or "revision control systems," store data which represents multiple versions of different documents, as indicated in FIG. 1A. In that Figure, the DATA is indicated, together with dashed loops which indicate the VERSIONs.

The loops indicate that the VERSIONs are contained in, and derivable from, the DATA. For example, each VERSION can be stored in its entirety. Alternately, a single VERSION can be stored in its entirety, and other VERSIONs can be stored in the form of differences between them and the single, entire VERSION.

The version control system reconstructs any selected VERSION for the user.

However, many such software systems suffer disadvantages. In general, some systems notify users of the occurrences of changes, but do not identify the changes themselves. Conversely, other systems identify the changes (generically, these systems are known as "diff" systems), but only in response to identification of a particular pair of documents.

SUMMARY OF THE INVENTION

One form of the invention observes a user's examination of a document contained in a repository. The invention then continually monitors that document for modifications. When the user examines the document at a later time, the invention presents the document in the current, later, form, and indicates the modifications occurring since the user last viewed the document.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a prior-art version control system.

FIG. 1B illustrates selected concepts involved in hypertext information retrieval.

FIG. 1 illustrates an illustrative embodiment of the invention.

FIG. 2 illustrates a hot list, and copying PAGEs from a REPOSITORY to an EXTERNAL SERVICE.

FIG. 3 illustrates an ARCHIVE within the EXTERNAL SERVICE, which contains copies of original versions of PAGEs, and changes made to the original versions.

FIG. 3A illustrates a display, generated by the invention, which lists various versions of a PAGE.

FIG. 3B illustrates a display, generated by the invention, which identifies PAGEs contained in a hot list which have changed.

FIG. 4 illustrates a current version of a PAGE, presented in a format which points out changes made since a previous version.

FIG. 5 illustrates hot lists for two users, as compared to a single user as in FIG. 2.

FIG. 6 is a flow chart illustrating logic implemented by one form of the invention.

FIG. 7 is a time-history of three PAGEs.

FIG. 8 is an architecture for part of one type of EXTERNAL SERVICE.

FIG. 9 illustrates one form of the invention.

FIG. 10 illustrates one form of the invention.

FIG. 11 illustrates output of HTMLDIFF, showing differences between a subset of two versions of

HTTP://SNAPPLE.CS.WASHINGTON.EDU.600/MOBILE/.

The original HTML source was edited manually to make the result fit onto one page; in practice, the highlighted changes would be interspersed among a much larger document. Small arrows point to changes, which are primarily additions in this case. The change in the "last update" date give an example of text being replaced. Here the page's author had highlighted the changes manually with small icons as well. The banner at the top of the page was inserted by HTMLDIFF.

FIG. 12 illustrates version histories which give the user a chance to compare any two versions, or to go directly to a selected version.

FIG. 13 illustrates output of W3NEWER, and shows a number of anchors (the descriptive text originates from the hot list). The anchors marked "changed" have modification dates after the time which the user's browser history indicates the URL was last seen. Some URLs were not checked at all, and others were checked and are known to have been seen by the user.

FIG. 14 demonstrates use of a SNAPSHOT facility, which allows a user to specify an operation on a URL. In this example, DOUGLIS@RESEARCH.ATT.COM is "remembering" URL HTTP://SNAPPLE.CS.WASHINGTON.EDU:600/MOBILE/.

DETAILED DESCRIPTION OF THE INVENTION

An illustrative embodiment of the invention is given in the discussion below.

Overview of Invention

A commonly used repository of information is known as the World Wide Web, or WWW. In the WWW, providers of information make their information available to users in the form of "pages." Each page is assigned a name, which distinguishes the page from other pages, and allows a user to locate the page.

The WWW provides information using an information retrieval-and-display approach called "hypertext." In hypertext, a page may contain references to other pages, or other documents. A user can call up a page which is referenced, by clicking on the reference (called a URL, or Universal Resource Locator) with a pointing device. FIG. 1B provides an example.

In FIG. 1B, a document D is displayed to a user. References R refer to other documents. For example, R1 refers to D1, R2 refers to D2, and so on. The referenced documents themselves may contain their own references to other documents, such as R4, which refers to D4.

A user can retrieve a referenced document D, by clicking on the reference R which refers to it. For example, clicking on R1 causes retrieval and display of D1.

Under the invention, a user of the WWW initially identifies pages of interest. Document D in FIG. 1B represents one page. These selected pages form a "hot list." Then, the invention does the following:

(a) Copies the hot-listed pages into an archive, which is a storage location separate from the WWW, and under independent control. After the copying, the original pages continue to reside in the WWW, and copies reside in the archive.

(b) Monitors, at later times, the original pages for changes, and archives the changes.

(c) Records the times when the user later accesses each hot-listed page.

(d) Whenever the user accesses a hot-listed page, presents the user with

i) the current version of the page (which may differ from the initial copy which was stored in the archive); and

ii) an option to compare selected versions of the page. The comparison is presented by performing a differencing operation on pairs of versions.

e) As an option, the invention also implements the steps described above with respect to documents referenced by the page. For example, in FIG. 1A, if a user is viewing document D, the invention can present the current version of reference document D2, together with a history of D2.

More Detailed Description

Hot-List Pages are Stored in EXTERNAL SERVICE

FIG. 1 illustrates a REPOSITORY of information, such as the WWW. For assistance in accessing the REPOSITORY, the invention provides the EXTERNAL SERVICE which includes:

(a) SOFTWARE, such as that provided in the COMPUTER PROGRAM LISTING herein,

(b) a SERVER, or other computer, which runs the software, and

(c) COMMUNICATION SYSTEMS which link with both the users and the REPOSITORY.

The SERVER and the COMMUNICATION SYSTEMS located within the EXTERNAL SERVICE are known in the art. As indicated in the Figure, the EXTERNAL SERVICE is distinct from the REPOSITORY, and under separate control.

The invention does not disrupt the users' normal interaction with the REPOSITORY; the users can interact with both the REPOSITORY, as usual, and also with the EXTERNAL SERVICE. Dashed arrows 3 indicate the interaction. Several examples will provide illustrative modes of operation of the invention.

EXAMPLE

Single User

Operation with respect to a single user will first be explained. FIG. 2 shows a hot list 4, submitted by USER 1, which identifies pages A and B as being of interest to USER 1. The invention allows the user to modify the hot list at later times. In response to the hot list, the invention copies pages A and B from the REPOSITORY, as indicated by the dashed arrows. These PAGEs will be termed "base pages." At this time, the originals of PAGEs A and B remain in the REPOSITORY, and copies reside in the EXTERNAL SERVICE.

Then, the invention periodically examines the originals of PAGES A and B, located in the REPOSITORY, for changes. In looking for changes, the invention first performs a preliminary check, based on information such as (1) dates of modification and (2) checksums.

Dates of modification may be added to a PAGE by the PAGE provider. These dates directly indicate whether the originally archived version has changed.

Checksums are generated by the invention. An example of a checksum is the numerical sum of all characters in a line, or on a page. If a checksum changes (indicating that the number of characters has changed), the change indicates a high probability that a change has occurred in the PAGE. (In practice, the checksums used are more complex than this simple example illustrates. Checksums are known in the art.)

If the preliminary check, either by dates of modification or checksums, indicates that changes have occurred, then the invention copies the present version of the PAGE into the EXTERNAL SERVICE, and compares it with the base page, in order to locate the changes. Computer programs for detecting such changes are known in the art, and some examples are given in the TECHNICAL APPENDIX. A preferred program, not known in the prior art, is entitled W3NEWER, and was developed by the inventors. W3NEWER is contained in the listing located at the end of this Specification.

When changes are found, the invention stores them in the EXTERNAL SERVICE. FIG. 3 illustrates storage of the changes, by the small boxes 6 located below PAGEs A and B. The DATEs within the boxes 6 indicate the dates on which the changes were saved.

FIG. 3A illustrates how the invention displays the history of versions. Column 7 indicates the number assigned to each version by the invention. Column 8 indicates the times when the respective versions were retrieved by the invention. Column 8A allows a user to select a, pair of versions for a differencing operation, as discussed below.

For ease of explanation, FIG. 3 illustrates storage of base pages, which are early versions of PAGEs, together with subsequent changes, indicated by the boxes 6. However, in practice, it can be more efficient to perform storage in a reversed sense, by storing the latest version as the base page (instead of the early version) and storing the changes 6 from which early versions can be reconstructed. One reason is that users are expected to call for latest versions more frequently than early versions. Storage of the entire latest versions eliminates the need to reconstruct them.

The changes, together with their base pages, form an archive, which allows reconstruction of a PAGE as of any date desired. For example:

PAGE A itself (ie, the base page), plus the changes labeled DATE 1, allow reconstruction of the version of PAGE A, as of DATE 1.

PAGE A itself, plus the changes labeled DATE 1 and DATE 2, allow reconstruction, as of DATE 2, and so on.

When USER 1 wishes to view PAGE A, the invention ordinarily retrieves and presents the current version. The invention also provides an option for reconstructing the PAGE, as of a date specified by the user, and presents it in the format shown FIG. 4. The program HTMLDIFF, contained in the listing, generates the image shown in FIG. 4. The content of the page can be divided into three classes.

The first class contains material which has not changed. This class of material is displayed in the font, size, color, and background, as customary in documents downloaded from the REPOSITORY.

The second class represents changes, and contains material not present in the base page, but which has been added. Brackets 9 indicate such material. (The brackets 9 are part of FIG. 4, and are not necessarily part of the page generated by the invention.) This material is presented in a particular font, particular size, particular color, and particular background. The choice of these parameters can be varied but, in general, they should be chosen to maximize contrast with the first class of material. In addition to the formatting described immediately above, the added material is further highlighted by arrows 7.

The third class contains material which was deleted from the base page. Deleted material can be handled in at least three ways. One, deleted material can be simply deleted, so that the page presented to the reader contains no reference to the deleted material.

Two, the deleted material can be deleted, but a reference indicating the deletion is added, such as the phrase "Deleted material occurs here." In this case, the user can be given the option of fetching the deleted, non-visible, material.

Three, deleted material can be presented, but indicated as deleted, as by "redline" format, in which a horizontal line, perhaps red in color, is drawn through the deleted material.

FIG. 3B illustrates a display, generated by the invention, which indicates which PAGEs on a user's hot list have undergone changes.

SECOND EXAMPLE

Multiple Users

In actual practice, multiple users are expected to use the invention. Each of them submits a hot list. In one approach of the invention, the procedure undertaken for a single user (described above) is repeated for multiple users: all PAGEs, on all hot lists, are copied into the EXTERNAL SERVICE. Then, for each hot list, the originals of the PAGES, located within the REPOSITORY, are monitored for changes, and the changes are retrieved into the EXTERNAL SERVICE, as described above.

However, this approach contains inefficiencies. For example, a given PAGE will probably be identified by more than one hot list. Repeatedly copying that PAGE, for each hot list, would entail storage of multiple copies of the same PAGE. Further, repeatedly comparing the multiple copies with their originals in the REPOSITORY represents a waste of computer time: a single comparison would suffice. The invention reduces these inefficiencies by the approach shown in FIG. 5.

This Figure represents a modification of FIG. 4, to which a hot list for USER 2 has been added. The added hot list specifies PAGES A and C.

To process the new hot list, the invention first checks whether the PAGEs identified on the added hot list are archived within the EXTERNAL SERVICE. Since PAGE A, plus its changes, are already contained within the archive, that PAGE is not copied. But PAGE C, which is not present in the ARCHIVE, is archived, as indicated by the dashed arrow.

At this time, all PAGEs identified on all hot lists are contained within the archive. To emphasize this fact, PAGE A is indicated twice: once for USER 1, and a second time by a dashed page 14, for USER 2, although, as stated above, PAGE A is stored only once.

After archiving all necessary PAGEs, the originals, located within the REPOSITORY, are periodically monitored for changes, as described above. The changes are copied to the archive of the EXTERNAL SERVICE.

Flow Chart

An exemplary flow chart is shown in FIG. 6, which refers to a single-user case. In block 20, the EXTERNAL SERVICE accepts hot lists from users. Then, in block 23, the EXTERNAL SERVICE checks whether the PAGEs identified on the hot lists are contained within the archive. If not, the PAGEs are copied from the REPOSITORY, as indicated by block 26.

Then the logic proceeds to block 29, where the originals of the PAGEs, located in the REPOSITORY, are examined for changes. The examination can include the preliminary checks (for checksums and dates of modification) discussed above. When changes are found, the entire PAGE containing them is downloaded to the EXTERNAL SERVICE, and the changes, indicated by blocks 6 in FIG. 3, are derived. Block 32 indicates relevant information stored in the EXTERNAL SERVICE.

As users access the PAGEs, block 35 monitors the times of the accesses, in order to identify which versions of each PAGE the user viewed last. These times are stored, as indicated by block 32 and dashed arrow 37. These times are used to determine which changes in FIG. 4 are to be identified as new material, when a PAGE is called by each user. An example will illustrate.

FIG. 7, top, illustrates the time-history of changes made to PAGE A. USER 1 accessed this PAGE at time 2, as indicated. Block 35 in FIG. 6 monitors and records this time (at TIME 2 in FIG. 7, and not earlier, of course).

If USER 1 again accesses the PAGE at time 5, then the invention presents VERSION 1 to the USER. However, if the user accesses the PAGE at time 11, VERSION 2 had been created since the last access by USER 1. The invention had previously identified the changes, and copied them as indicated in FIG. 3. Now, at the access at time 11, the invention presents VERSION 1, plus the changes which make VERSION 2, because block 35 in FIG. 6 indicates that the USER has not seen VERSION 2.

Returning to the flow chart of FIG. 6, block 39 indicates that, when a USER calls for a PAGE, the invention presents the current version, and indicates the changes made (as in FIG. 4) since the USER last accessed that page. In the example immediately above, the invention presents VERSION 2 of PAGE A, as in FIG. 7, and indicates the changes made since VERSION 1, because VERSION 1 was the last accessed by USER 1.

The flow chart of FIG. 6 should not be read as limiting the invention to a linear, sequential mode of operation. In practice, multiple users can present hot lists simultaneously, and other operations shown in the flow chart can also occur together.

THIRD EXAMPLE

Notification of Changes

The invention can notify USERs when changes in their hot-listed PAGEs occur, as indicated by the dashed block 40 in FIG. 6. This notification can take the form of a flag which is associated with the BASE PAGE in FIG. 8. When the USER logs into the EXTERNAL SERVICE, the invention notifies the USER of the changes to the respective PAGEs. FIG. 3B illustrates one approach to identifying PAGEs which have changed.

Other types of notification are possible. For example, the invention need not wait for a user to access a PAGE. The invention can notify the user when changes have been found, as by sending an electronic mail message to the user.

FOURTH EXAMPLE

Common Hot List

The invention can maintain a predetermined hot-list, for a community of users. This hot list contains a list of PAGEs which are considered to be of general interest to the community. This hot list, and the PAGEs identified on it, are made publicly available, to all users, but on a read-only basis. Users cannot modify the hot list, or the pages.

This predetermined hot list can serve as an instructional tool, to educate users in the operation of the invention, and to demonstrate desirable features.

One Architecture of Data Storage

An illustrative approach to storage of the information identified in block 32 of the flow chart of FIG. 6 is illustrated in FIG. 8, which is explained with reference to FIG. 7.

FIG. 7 illustrates hypothetical changes to the three PAGEs identified by the two hot lists of FIG. 5. PAGE A underwent changes at times 7 and 13. Page B underwent changes at time 10, and so on.

In FIG. 8, the arrows extending from the symbols "USER 1", etc., indicate the times of access by the users. For example, USER 1 accessed PAGE A, VERSION 1, at time 2. USER 1 then accessed PAGE A, VERSION 2, at time 9, and so on.

The invention maintains a TABLE of these times, as indicated on the right side of FIG. 8, together with a list of PAGEs, or documents, owned by each USER. Ownership is determined by the hot lists. The invention also maintains (a) the BASE PAGES, (b) the changes to each, and (c) the times of each change, as indicated on the left side of the Figure. From this data, the invention is able to reconstruct any PAGE, as of any date subsequent to the date of the BASE PAGE.

Additional Considerations

1. One definition of "page" is that it refers to a unit of data, stored in a system, which is identified by a specific name. (In the WWW, all pages have unique names.) Other terms can refer to such units of data, such as "files" and "documents." In general, the particular name used will depend on the system storing the data.

2. One definition of "repository" is a collection of data, which is accessible by computer. The repository may be available to the public, or access may be limited. In general, repositories are expected to be distributed, meaning that the storage locations are physically distributed over a wide geographic area, and linked together by a communication system.

3. It was stated above that the invention can reconstruct a page as of any selected date. The reconstruction is based on the changes 6 in FIG. 3. These changes are detected periodically, and the periodicity is determined by each user of the system, subject to limits imposed by the designer and system administrator.

For example, user A can specify a period of one day for checking for changes in the pages on user A's hot list; user B can specify a different period for B's pages, such as one week. The system administrator can specify that no period, for any user, can be shorter than one hour.

Consequently, changes in a page, located in the REPOSITORY, will only appear in a reconstruction done by the EXTERNAL SERVICE after the changes have been detected, and not earlier. An example will illustrate this distinction.

Assume that the invention looks for changes on odd-numbered dates. Thus, a change occurring on the fourth of a month will be detected on the fifth. However, if a user happens to call for reconstruction on the fourth, the change occurring on the fourth will not appear in the reconstruction. Only changes occurring as of the prior detection, namely, as of the third, will appear.

It is expected that the detection process will be performed sufficiently often that the influence of this factor will be negligible.

4. The invention can extend its differencing function (ie, the examination of pages for changes) to pages referenced by the page accessed by the user. For example, if the user accesses document D in FIG. 1B, the invention can detect changes in all documents referenced by document D, such as D1, D2, and D3.

In another embodiment, the differencing can extend to the documents which are, in turn, referenced by the referenced documents. For example, the referenced documents (D1, D2, and D3) refer to D5 and D6. These latter documents (D5 and D6) can be differenced also, as can be the documents which they reference, and so on.

5. The invention provides all information from which a current version of a PAGE may be derived. FIG. 4 gives an example. FIG. 4 contains all such information, together with other information which indicates changes since a previous version.

6. The discussion above presumed that comparison, or differencing, between different versions of a PAGE was done within the EXTERNAL SERVICE. This is not strictly necessary; the comparison can be done at any convenient location. Further, the preliminary checking for the existence of changes can be done at any convenient location.

7. In data storage systems, names are given to the units of information (e.g., documents, pages, records), although the names can be different in different databases. However, the names of the units, in general, remain the same throughout time, despite changes which are made to the information contained in the unit. Therefore, one definition of the term "version" refers to a unit of information, which is different from a previous unit of the same name.

8. The REPOSITORY in FIG. 1 is, in general, located remotely from the EXTERNAL SERVICE. Communication is undertaken by any convenient approach, such as a public-access communication network known as the INTERNET.

In general, the REPOSITORY is under independent control of the EXTERNAL SERVICE. One ramification of this independent control is that the type of processing done to the PAGEs copied into the EXTERNAL SERVICE is controlled by the EXTERNAL SERVICE, and not by the REPOSITORY. For example, (a) the particular processes used in locating and storing differences, (b) the frequency of processing, and (c) the mode of notifying a user, are controlled by the designer of the EXTERNAL SERVICE. The operator of the REPOSITORY has no involvement in this processing.

9. FIG. 9 illustrates another form of the invention. The invention maintains base pages 30 within the EXTERNAL SERVICE, as required by the hot lists 36. The base pages 30 were downloaded from respective repositories 42A, 42B, etc.

The invention periodically monitors the originals 30A of the pages, located in the repository 42, for changes, and stores the changes within the EXTERNAL SERVICE. The invention notifies users when changes are found in pages on their hot lists (notification is not shown).

A version control system 39 allows users to fetch and view any version of any page.

10. The different versions of documents may contain drawings, files from which sound maybe generated, files which produce video clips and animation, and other components which do not consist strictly of alphanumeric characters. The invention detects the existence of changes in such components, and marks the existence of the changes, in the display as shown in FIG. 4, without necessarily identifying in detail the nature of the changes.

11. A primary use of the invention is envisioned in the situation shown in FIG. 10. The EXTERNAL SERVICE obtains copies of PAGEs from a REPOSITORY, such as WWW. However, the EXTERNAL SERVICE is given no authority to replace or modify the pages contained in the REPOSITORY. To the EXTERNAL SERVICE, the PAGEs represent read-only data, as indicated by the "X" over arrow 50, which indicates a write operation.

The EXTERNAL SERVICE performs differencing between currently copied versions of pages, and DATA representing previous versions. The DATA stored in the EXTERNAL SERVICE can be both read, and written to, by the EXTERNAL SERVICE. The EXTERNAL SERVICE reconstructs any version on demand, and also indicates differences between any two versions selected by a user, as discussed above. These functions can be accomplished by a prior-art Revision Control System, RCS (also called a Version Control System), or by the code contained in the listing contained in this Specification.

12. In one form of the invention, the PAGEs retrieved are written in a "markup language," such as HyperText Mark-up Language (HTML). A mark-up language, in general, contains two types of codes, interspersed among the actual text of a document.

One type indicates how the PAGEs are to be displayed. For example, some codes indicate paragraph indentation, other codes indicate font styles, yet other codes indicate style of font, within a font, such as italicizing, underlining, double-striking, or bold printing. This type of code is referred to as format-defining.

A second type of code can identify an image, such as a bit-mapped file located elsewhere. When such a code is read by the system displaying the PAGE, a copy of the image is retrieved, and displayed within the PAGE, at the location specified by the code. This type, of code is referred to as content-defining.

The invention does not treat changes in the format-defining codes as changes in content. Thus, a PAGE which changes in layout, or typestyle, only, is not designated as a changed page.

The differencing program contained in the COMPUTER PROGRAM LISTING compares different versions on a subunit-by-subunit basis. For example, the program compares corresponding sentences in different versions, and the sentences are detected by sentence terminators. (Longer subunits can be used, such as paragraphs or pages.) The sentence terminators are a subset of the markup language. Specifically, the terminators are format-defining codes.

                     COMPUTER PROGRAM LISTING
      The program listing is divided into three sections.
      1. HTMLDIFF, comprising:
          --  html_diff.sml (5 pages),
          --  diff.sml (3 pages),
          --  mlweb.sml (4 pages), and
          --  html.lex (one page).
      2. W3NEWER (17 pages).
      3. NOHANDS, comprising:
          -- nohandsBE  (11 pages),
          -- no-hands.cgi (3 pages),
          -- rcsdiff.cgo (4 pages), and
          -- snapshot.cgi (3 pages).
      NOHANDS is an overall program set which utilizes W3NEWER and
      HTMLDIFF.

                             TABLE 1
        An example of the thresholds specified to w3newer.
        # Comments start with a sharp sign.
        # perl syntax requires that "." be escaped
        # Default is equivalent to ending the file with ".*"
        Default                                       2d
        file:.*                                       0
        http://www.backslash..yahoo.backslash..com/.* 7d
        http:www.backslash..research.backslash..att.backslash.com/.* 0
        http://.*.backslash..att.backslash..com/.*    1h
        http://home.backslash.. mcom.backslash..com/honse/whatsnew/- 12h
        whats_new.backslash..html
     http://www.backslash..ncsa.backslash..uiuc.backslash..edu/SDG/Software/-
     12h
        Mosaic/ Docs/whats-new.backslash.html
        http://snapple.backslash..cs.backslash..washington.backslash..edu:600/-
     1d
        mobile/
        # rarely modified
        http://www.backslash..cs.backslash..duke.backslash..edu/ pk/- 7d
        HomePage.backslash.. html
        # this is in my hotlist but will be different every day
        http://www.backslash..unitedmedia.backslash..com/- never
        comics/dilbert/

• Inventors
  Ball, Thomas J.; Douglis, Frederick;
• Assignee
  AT&T Corp. (New York, NY)
• Published
  Apr-2-2002
• Current US Classes:
  715/511
• Application #
  549359
• International Classes
  G06F 017/21
• Field of Search
  395/148 395/772 707/511 707/501 707/513 707/203 707/202 707/204
• Examiner
  Feild; Joseph H.
• US Patent References:
  4807182
  4912637
  5008853
  5278979
  5325478
  5438661
  5535332
  5671428
  5752245
  5764972
  5806078
  5835601
  5835911
  5860071
  5995097