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Temporal Queries in XML Document Archives and Web Warehouses

Temporal Queries in XML Document Archives and Web Warehouses. Author: Fusheng Wang and Carlo Zaniolo. Publication: TIME-ICTL’03, IEEE. 報告人：陳建宏. outline. Main Issue Previous Work A Logical Model for Versions Complex Queries Conclusions. outline. Main Issue Previous Work

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Temporal Queries in XML Document Archives and Web Warehouses

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  1. Temporal Queries in XML Document Archives and Web Warehouses Author: Fusheng Wang and Carlo Zaniolo Publication: TIME-ICTL’03, IEEE 報告人：陳建宏

  2. outline • Main Issue • Previous Work • A Logical Model for Versions • Complex Queries • Conclusions

  3. outline • Main Issue • Previous Work • A Logical Model for Versions • Complex Queries • Conclusions

  4. Main issue • Concisely representing the successive versions of a document as an XML document that implements a temporally grouped data model • Using XML query languages, such as XQuery, to express complex queries on the content of a particular version, and on the temporal evolution of the document elements and their contents

  5. outline • Main Issue • Previous Work • A Logical Model for Versions • Complex Queries • Conclusions

  6. Temporal XML Representation • A valid tag for XML/XHTML documents is proposed to support valid time • A data model is proposed for temporal XML documents • XML query languages such as Xpath and XQuery <valid> <validity from=“1980-01-01” to=“1985-12-31”/> This is test </valid> <title time:valid="2000-01-01, 2000-01-09">XML</title> <title time:valid="2000-01-10, now">Introduction to XML</title> Xquery example: select all the title elements in the "books.xml" file doc("books.xml")/bookstore/book/title

  7. Change Detection How to know the difference between the latest version and the previous one? There are some of efficient change detection algorithms • Ladiff • XyDiff • X-Diff

  8. Managing the Deltas There are different schemes for storing these deltas on secondary storage and processing them for version reconstruction and query execution • Revision Control System (RCS) scheme • Reference-Based Version Model(RBVM) scheme • Source Code Control System(SCCS) scheme

  9. Temporal Databases • Many temporal data models are proposed already. They are classified into two main categories • Temporally ungrouped • Temporally grouped

  10. outline • Main Issue • Previous Work • A Logical Model for Versions • Complex Queries • Conclusions

  11. XML REPRESENTATION of versioned document • V-Document • Each element is assigned with two attributes vstart and vend, which represent the valid version interval of the element • In V-Document, we represent each attribute by a sub-element denoted by a special flag attribute isAttr.

  12. Sampled versioned xml documents version 2002-01-01 <document> <chapter no="1"> <title>Introduction</title> <section>Background</section> <section>Motiviation</section> </chapter> </document> version 2002-01-02 <document> <chapter no="1"> <title>Introduction and Overview</title> <section>Background</section> <section>History</section> </chapter> <chapter no="2"> <title>Related Work</title> <section>XML Storage</section> </chapter> </document> version 2002-01-03 <document> <chapter no="1"> <title>Introduction and Overview</title> <section>Background</section> <section>History</section> </chapter> <chapter no="2"> <title>Related Work</title> <section>XML Indexing</section> </chapter> </document>

  13. V-document Example Attribute of element ”chapter” <document vstart="2002-01-01" vend="now"> <chapter vstart="2002-01-01" vend="now"> <no isAttr="yes" vstart="2002-01-01" vend="now">1</no> <title vstart="2002-01-01" vend="2002-01-01">Introduction</title> <title vstart="2002-01-02" vend="now">Introduction and Overview</title> <section vstart="2002-01-01" vend="2002-01-01">Motivation</section> <section vstart="2002-01-01" vend="now">Background</section> <section vstart="2002-01-02" vend="now">History</section> </chapter> <chapter vstart="2002-01-02" vend="now"> <no isAttr="yes" vstart="2002-01-02" vend="now">2</no> <title vstart="2002-01-02" vend="now">Related Work</title> <section vstart="2002-01-02" vend="2002-01-02">XML Storage</section> <section vstart="2002-01-03" vend="now">XML Indexing</section> </chapter> </document> vstart and vend tag

  14. V-document advantage • No storage redundancy • The changes are naturally representated • Temporal queries are easily expressed on V-documents

  15. Change operations - update • UPDATE <document> <chapter no="1"> <title>Introduction</title> <section>Background</section> <section>Motiviation</section> </chapter> </document> <title vstart="2002-01-01" vend=“now"> Introduction </title> <title vstart="2002-01-01" vend="2002-01-01"> Introduction </title> <title vstart="2002-01-02" vend="now"> Introduction and Overview </title> <document> <chapter no="1"> <title>Introduction and Overview</title> <section>Background</section> <section>History</section> </chapter>

  16. Change operations - insert • INSERT <section vstart="2002-01-01" vend="now"> Background </section> <document> <chapter no="1"> <title>Introduction</title> <section>Background</section> </chapter> </document> <section vstart="2002-01-01“ vend="now"> Background </section> <section vstart="2002-01-02" vend="now"> History </section> <document> <chapter no="1"> <title>Introduction and Overview</title> <section>Background</section> <section>History</section> </chapter>

  17. Change operations - DELETE • DELETE <section vstart="2002-01-01" vend="now"> Motivation </section> <document> <chapter no="1"> <title>Introduction</title> <section>Background</section> <section>Motivation</section> </chapter> </document> <section vstart="2002-01-01" vend="2002-01-01"> Motivation </section> <document> <chapter no="1"> <title>Introduction and Overview</title> <section>Background</section> </chapter>

  18. outline • Main Issue • Previous Work • A Logical Model for Versions • Complex Queries • Conclusions

  19. Sampled versioned xml documents version 2002-01-01 <document> <chapter no="1"> <title>Introduction</title> <section>Background</section> <section>Motiviation</section> </chapter> </document> version 2002-01-02 <document> <chapter no="1"> <title>Introduction and Overview</title> <section>Background</section> <section>History</section> </chapter> <chapter no="2"> <title>Related Work</title> <section>XML Storage</section> </chapter> </document> version 2002-01-03 <document> <chapter no="1"> <title>Introduction and Overview</title> <section>Background</section> <section>History</section> </chapter> <chapter no="2"> <title>Related Work</title> <section>XML Indexing</section> </chapter> </document>

  20. Query 1 • Snapshot queries: retrieve the version of the document on 2002-01-03: for $e in document("V-Document.xml") /document return snapshot( $e,"2002-01-03“) <document vstart="2002-01-01" vend="now"> <chapter vstart="2002-01-01" vend="now"> <no isAttr="yes" vstart="2002-01-01" vend="now">1</no> <title vstart="2002-01-02" vend="now">Introduction and Overview</title> <section vstart="2002-01-01" vend="now">Background</section> <section vstart="2002-01-02" vend="now">History</section> </chapter> <chapter vstart="2002-01-02" vend="now"> <no isAttr="yes" vstart="2002-01-02" vend="now">2</no> <title vstart="2002-01-02" vend="now">Related Work</title> <section vstart="2002-01-03" vend="now">XML Indexing</section> </chapter> </document>

  21. Query 2 • Change queries: retrieve the unchanged elements between the version on 2002-01-01 and the version on 2002-01-03: for $e in document("V-Document.xml") /document return diff-identical($e,"2002-01-01","2002-01-03") <document vstart="2002-01-01" vend="now"> <chapter vstart="2002-01-01" vend="now"> <no isAttr="yes" vstart="2002-01-01" vend="now">1</no> <section vstart="2002-01-01" vend="now">Background</section> </document>

  22. Query 3 • Evolutionary queries: find the history of the title of chapter 1: for $title in document("V-Document.xml") /document/chapter[no="1"]/title return $title <title vstart="2002-01-01" vend="2002-01-01">Introduction</title> <title vstart="2002-01-02" vend="now">Introduction and Overview</title>

  23. Query 4 • Continuous queries: find titles that didn’t change for more than 2 consecutive years. for $title in document("V-Document.xml") /document/chapter/title let $duration := substract-dates( $title/@vend, $title/@vstart) where dayTimeDuration-greater-than( $duration, "P730D") return $title <title vstart="2002-01-02" vend="now"> Introduction and Overview </title>

  24. Query 5 • A Since B: find chapters in which section “History” remains unchanged since the version when the title was changed to “Introduction and Overview”. for $ch in document("V-Document.xml") /document/chapter let $title := $ch/title[ title="Introduction and Overview"] let $sec := $ch/section[section="History"] where not empty($title) and not empty($sec) and $sec/@vstart = $title/@vstart and $sec/@vend ="now" return $ch <chapter vstart="2002-01-02" vend="now"> <no isAttr="yes" vstart="2002-01-02" vend="now">1</no></chapter>

  25. Query 6 • A Until B: find chapters in which the title didn’t change until a new section “History” was added for $ch in document("V-Document.xml") /document/chapter let $title := $ch/title[1] let $sec := $ch/section[section="History"] where not empty($title) and not empty($sec) and $title/@vend = $sec/@vstart return $ch <chapter vstart="2002-01-01" vend=“2002-01-01"> <no isAttr="yes" vstart="2002-01-01" vend="now">1</no> </chapter>

  26. Join Query • Joins: find the chair of employee ’Bob’ on 1996-01-31: for $e in document("employees.xml") /employees/employee[name=’Bob’] for $d in document("depts.xml")/depts/dept let $et := snapshot($e,"1996-01-31") let $dt := snapshot($d,"1996-01-31") where not empty($et) and not empty($dt) and $et/dept = $dt/name return $dt/chair

  27. outline • Main Issue • Previous Work • A Logical Model for Versions • Complex Queries • Conclusions

  28. Conclusions • We can represent a multi-version document in V-Document • In this representation scheme, complex queries can be expressed easily

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