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Extending Temporal Database Concepts to the World Wide Web

Explores integrating temporal database concepts into the web, addressing transaction and valid time, historical web documents, and management of temporal versions for more efficient information retrieval and browsing.

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Extending Temporal Database Concepts to the World Wide Web

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  1. Extending Temporal Database Concepts to the World Wide Web Fabio Grandi, Maria Rita Scalas C.S.I.TE.-C.N.R., D.E.I.S.University of Bologna, Italy

  2. The TDB challenge • Time is a pervasive information component • TDBs are a consolidated research field • A large infrastructure has been developed • formal concepts • data models • query languages • index structures • ...

  3. The WWW blast • The World Wide Web is: • the new on-line information universe • easy to use by its hypermedia nature • suitable to continuous evolution • with ever growing information contents • Temporal aspects neglected so far(with unexploited potentialities)

  4. Towards a Temporal Web • Extension of TDB concepts (and technology) to the Web • Transaction time • Valid time • Database integration

  5. Transaction time • Transparent evolution of Web documents • Access to “out-of-date” document versions • due to changes in the Web itself • due to changes in the document contents • due to “temporary” heterogeneous documentsperiodically available at the same URL

  6. Valid time • Web representation of changing information • Historical Web documentswith timestamped items • Selective temporal browsing of documents • efficient retrieval of historical information(museums, libraries, encyclopaedias) • services with time schedules(e.g. conference cfp, promotional campaign) • ...

  7. Database Integration • Integration between Web and Databases(one or both Temporal) • Automatic updates of Web pageswith a companion DB server • temporal DB aspects (timestamped data) • real-time DB aspects (deadlines, consistency) • active DB aspects (triggers, update rules)

  8. Temporal Web extensions • Temporal server solution • requires extensions to the HTTP protocol • snapshot resources delivered by version-aware servers to standard clients • Temporal client solution • requires extensions to the HTML language • temporal resources from standard serverslocally processed by version-aware clients

  9. Transaction time - solutions • Versioning granularity: Web resource • Navigation context (client): time point • Version negotiation (HTTP extension) • Temporal selection on the server side • version naming scheme compatible with standard file systems • indexing techniques to improve efficiency

  10. Management of TT-Versions • Uniform naming scheme [Ota et al.] • resource doc.html with 3 versions on host www.server.it in directory /pub/ : 03-Feb-95 /pub/doc.html/1 25-Jan-96 /pub/doc.html/2 17-Mar-97 /pub/doc.html/3 • meta links - explicit URL of ver. 3: http://www.server.it/pub/doc.html/3 • HTTP extension for version negotiation:GET http://www.server.it/pub/doc.html Content-Version : ”3”

  11. Valid time - solutions • Versioning granularity: single resource item • Navigation context (client): time interval • Temporal documents (HTML extension) • Temporal selection on the client side • local selective document browsing • no network re-fetch for changes of context

  12. Management of VT-Versions • HTML extension for data timestamping • new HTML element: validity context • new “valid-time” tag: vt • new attributes in vtstart-tag: from and to<!-- valid-time timestamping > <vt from=”DATE 01/01/1980” to=”DATE 12/31/1985” > text here is <b>valid from 1980 to 1985</b> </vt>

  13. Temporal User Interfaces • Visual tools for temporal context selection • direct data entry (dialog window) • granularity selection (pop-up menu) • time point selection (cursor) • interval length selection (“thick” cursor) • Capture of valid-time from document items • Transaction-time history of resources

  14. Other temporal aspects • Multiple transaction time, valid time, user-defined time dimensions? • Time dimensions intrinsic to multimedia data (music, movies...) • Time dimensions usedin cache-validation HTTP mechanisms • User’s navigation histories

  15. Future work • Prototype implementation • TT support with a temporal server • VT support with a temporal client • Database integration • Interaction between temporal aspects

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