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Thomas Triebsees Universität der Bundeswehr München Department of Computer Science

A Theory for Model-based Transformation Applied to Computer-Supported Preservation in Digital Archives. Thomas Triebsees Universität der Bundeswehr München Department of Computer Science Thomas.Triebsees@unibw.de Tucson, 27th March 2007. Agenda. Research Context Motivating Example

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Thomas Triebsees Universität der Bundeswehr München Department of Computer Science

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  1. A Theory for Model-based Transformation Applied to Computer-Supported Preservation in Digital Archives Thomas Triebsees Universität der Bundeswehr München Department of Computer Science Thomas.Triebsees@unibw.de Tucson, 27th March 2007 Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science

  2. Agenda Research Context Motivating Example Declarative, Preservation-Centric Approach for Model Transformation Preservation Language Results / Conclusions / Remarks Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science

  3. Research Context • Long-term preservation of digital material • Two facets: • Preservation procedure • Technical environment • Preservation approaches: • Emulation • Migration • Hybrid • Technical environment • usually highly modularized and complex } preserve information Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science

  4. Motivating Example Customer User Archive Archiver Browser store extractMetadata EXPOSE CI BII UI storePerm respond REQUEST / RESPONSE INGEST Permanent Storage Web Storage PStorage 1 PStorage 2 PStorage m Server 1 Server 2 Server n ... ... Transformation Integratable into system specifications Appropriate language elements Abstraction from different implementations Contribution:Declarative, domain-specific, preservation-centric language that facilitates to specify preservation requirements Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science

  5. Declarative, Preservation-Centric Approach for Model Transformation Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science

  6. Archive StateA' Archive StateA System StateA System StateA' System StateA'' basic operation (set association) Approach – System Model and Transformation Semantics Model elements • Typed Entities • Associations • Functions Transformation algorithm = sequence of basic operations basic operation (create object) Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science

  7. Approach - Preservation Concept (= semantic property) implements implements specify pre- servation of … … Context n Context 1 defines Constraints Preservation language used to generate / implement respect Transform. algorithms source context target context Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science

  8. Example – Abstraction through Contexts and Concepts ContextAWeb ConceptWebsite ContextBWeb AWeb <name> src … Website … 0..1 <name>.html φ (FOPL) … eP BWeb 1 * 1 <name> Folder HTMLFile 0..1 1 1 <name>.html html … * * … File Tag … resources trg … PDFFile ψ (FOPL) … … Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science

  9. Example – Specifying the Preservation Task Calculation Concept Website source <name> start.html … AWeb … calculation2005 <name>.html … Website calc.pdf 0..1 overview <name> eP doclist.html <name>.html 1 1 Folder δ HTMLFile html EXPOSE … … … … … resources ? BWeb … … … Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science

  10. Example - Typed Entities name : String location : String content : Tag start.html HTMLFile h:HTML <html> <head/> <body> … <a href=“…“></a> … </body> </html> start.html <html> t11:Tag <head> <body> t111:Tag t112:Tag name : String attrs : Seq<String x String> content : Seq<(String | Tag> Tag <title> <a> t1121:Tag t1111:Tag Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science

  11. Preservation Language Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science

  12. Archive StateA' Archive StateA' System State A System StateA' trans(δ | h → h‘) name = "start.html" location = "/… /source" content = <...> name = ? location = ? content = ? δ(h):HTMLFile h:HTMLFile δ Preservation Language – Transformation Constraints h → HTMLFile h h‘ Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science

  13. presO(h → HTMLFile, h[HTMLFile-{}]) location, content name name = "start.html" location = "/…/source" content = <...> name = "start.html" location = ? content = <...> δ(h):HTMLFile h:HTMLFile location, content HTMLFile-{} name δ Preservation Language – Object Preservation Constraints h → HTMLFile trans(δ | h → h‘) post(δ) ≡ { name(h‘) = name(h) } Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science

  14. Preservation Language – Concept Preservation Constraints presK({w → Website}, Website(w,f,h), AWeb, BWeb) location, content presO(h → HTMLFile, h[HTMLFile-{ }]) Concept Website Context AWeb Context BWeb δ „Calculation“ w: „Calculation“ δ(w): ____________ eP eP „source“ „start.html“ δ(f): ________ δ(h): __________ f: „source“ h: „start.html“ f‘: „html“ f‘‘: „resources“ Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science

  15. Results / Conclusion / Remarks Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science

  16. Conclusion • Constraint definitions show generality (abstraction from specification language) • Prototypical implementation available • Website migration example: • ≈ 300 files • ≈ 20 concepts • ≈ 700 constraints • ≈ 2300 affected objects Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science

  17. Conclusion Strengths: • State-based approach • Powerful object model • Abstraction via concepts; specification language need not necessarily be FOPL • Intuitive constraint definition for application domain • Coherently formal underpinning • Limits: • Generation of parallel migration algorithms • Undecidability of FOPL • Generating algorithms for comprehensive model reconstructions • Efficiency Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science

  18. Subject to your questions… ? Thomas Triebsees Universität der Bundeswehr München Department of Computer Science Thomas.Triebsees@unibw.de Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science

  19. Constraint-based Migration Advantages of declarative approach • easily integratable into system specifications • focus on critical issues • abstraction from implementation, thus platform independent • formal treatment possible Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science

  20. target model instance source model instance concept def. constraints (2) Concept recognition (5) Post- processing (1) Pre- processing (3) Algorithm generation (4) Algorithm execution extended object model target object model object model migration alg. Approach Conceptual overview Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science

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