1. Typing OpenDLib Repository Service: Strengths of an Information Object Type Language 1st European Workshop on the use of information object Repository Systems in Digital Libraries (DORSDL), in conjunction with ECDL2006 Leonardo Candela, Donatella Castelli Paolo Manghi, Pasquale Pagano Centro Nazionale delle Ricerche Pisa, Italy

2. DORSDL Workshop - 21 th of September, 2006 2 Outline DB Systems  Consolidated Systems based on Typed Data Models  General purpose approaches for building DB Applications  Types are good: application development and storage optimization Digital Libraries identify specific application domains  Current Repository Services provide rich storage support  (Type-less) Information Object Models  DL should be built on Systems that support Types for DL Our ideas…  Type Algebra for DLs  Develop Typed Repository Service Conclusions and Future issues Questions and discussion…

3. DORSDL Workshop - 21 th of September, 2006 3 DBMS DB Systems: realizing a DB Application System Interface DBMS Typed Data Model (Type Language) Application

4. DORSDL Workshop - 21 th of September, 2006 4 DBMS DB Systems: type definition System Interface DBMS Application Managers Typed Data Model (Type Language) Projects

5. DORSDL Workshop - 21 th of September, 2006 5 DBMS DB Systems: storage creation System Interface DBMS Application MP Typed Data Model (Type Language) Managers Projects

6. DORSDL Workshop - 21 th of September, 2006 6 DBMS DB Systems: Application Usage System Interface DBMS Application MP Typed Data Model (Type Language) Managers Projects Component on Managers and Projects

7. DORSDL Workshop - 21 th of September, 2006 7 DBMS DB Systems System Interface DBMS Application D1D2 MP Typed Data Model (Type Language) Managers Projects Component on Managers and Projects

8. DORSDL Workshop - 21 th of September, 2006 8 DB Systems: additions System Interface DBMS Application D1D2D3 Budgets Component on Managers and Projects Component on Budgets MPB Typed Data Model (Type Language) Managers Projects

9. DORSDL Workshop - 21 th of September, 2006 9 Relational DB System System Interface Relational DBMS Application D1D2D3 TabMTabPTabB Relational Model (SQL schema) Component on Managers and Projects Component on Budgets Table Budgets Table Managers Table Projects

10. DORSDL Workshop - 21 th of September, 2006 10 Typed Data Models: advantages Application development and maintenance  Functionality and content are kept independent from each other  Type correctness: components must be type- conformant  Modularity  Reuse: component-wise and data wise

11. DORSDL Workshop - 21 th of September, 2006 11 Typed Data Models: advantages Type-driven physical storage  Data integrity: data can be handled according to their associated structure only  Type information can be exploited to optimize space storage and access time

12. DORSDL Workshop - 21 th of September, 2006 12 DL Applications and (Type-less) Repository Services DL Applications are built exploiting Repository Services Repository Services concentrate on physical management of Information objects Based on a Type-less Information Object Model Offer a set of primitives to  Manage an Information Space of information objects: add, delete, update, search  Manage metadata records: efficient storing (XML), indexing, mapping, harvesting, publishing, etc.  Extra features: behaviors, communities, users… Historical reasons:  Originally DLs were flat catalogues of pairs file-metadata or metadata only

13. DORSDL Workshop - 21 th of September, 2006 13 Gaps of Type-less Repository Services DL Applications must “encode”  The notion of typed collection of information objects, seen as a collection of objects with the same structure - Prototypes address this problem (K. Saidis et Al, ECDL2006)  The notion of methods (functionality) of the objects of a given typed collection Applications are hard to write, maintain, reuse, and extend No type safety and data integrity  The objects into the store are not aware of their type All the advantages of DB Systems are lost…

14. DORSDL Workshop - 21 th of September, 2006 14 Gaps of Type-less Repository Services System Interface Repository Service Information Object Model Application Objects Component on Objects and Rep primitives Component: Typed Collections and methods data

15. DORSDL Workshop - 21 th of September, 2006 15 Things have changed… DL Applications are becoming common DL specific issues arise, regarding both information spaces and functionalities Need for systematic approaches, in order to maximize reuse and minimize effort  Systems for supporting DL-specific, customizable, and optimized functionalities to DL Applications designers and developers

16. DORSDL Workshop - 21 th of September, 2006 16 Things have changed… Information Space Towards richer Information Object Models  Collections of Complex objects: MF, files, relations, and behaviors  Structured Objects: objects as a compound of other objects, e.g. photo albums, etc.  Dynamic Objects: dynamic created content  Object features: provenance and preservation  Users-Objects relationship: copyrights, access rights, authentication, etc.  Others…

17. DORSDL Workshop - 21 th of September, 2006 17 Things have changed… Functionalities Towards system primitives  User profiling  User recommendations  Object Versioning  OAI-PMH Harvesting  Virtual Object Collection management  Others…

18. DORSDL Workshop - 21 th of September, 2006 18 Our goal Design and develop a Typed Repository Service, along the line of DB Systems Typed Information Object Model (OO) CollectionTable Relational Model Type algebraRelational Algebra

19. DORSDL Workshop - 21 th of September, 2006 19 Typed Repository Service A type defines a set of objects with the same structure and the operations (methods) that can be applied to them A Collection is a named set of objects defined according to the type assigned to the Collection A Repository Service Instance is a set of Collections A Repository Service “exposes” to Applications components all Collections defined in its active Instance Applications can manage, search, and manipulate objects of Collection according to the methods (functionalities) exposed by the relative type

20. DORSDL Workshop - 21 th of September, 2006 20 Typed Repository Service System Interface Typed Repository Service Typed Information Object Model (Type algebra) Application DO1DO2DO3 ArticlesNotesRefs Component on Notes and Refs Component on Articles ANR Type Collection

21. DORSDL Workshop - 21 th of September, 2006 21 DL Type Algebra A Type is characterized by:  A (possibly empty) set of type properties, i.e. attributes that depend on the Type features  A (possibly empty) set of Metadata Fields (MF) describing all objects of the Type, to be defined by the DL Designer A Collection of a given Type offers the primitives (methods) to  Search objects according to type properties  Search objects according to the MF  Add and Delete objects into and from the Collection

22. DORSDL Workshop - 21 th of September, 2006 22 DL Type Algebra Coll ::= Name = Type, Coll | Name = Virtual(Q, Name) |  Type ::= Raw(MF, FileFormats, behaviors) | Relation(MF, Type 1, Type 2, [1:1|1:n|n:n]) | Aggregation(MF, Type) | Union(Name 1,…,Name n ) | RawView(MF, FileFormats, behaviors) | Name | Others

23. DORSDL Workshop - 21 th of September, 2006 23 Raw type: “ground” objects Raw(MF, file formats, behaviors(in, out))  Object methods Update MF Upload manifestation/change link Update behaviors  Class methods Search by MF Search by full-text

24. DORSDL Workshop - 21 th of September, 2006 24 Relation Type: “association” objects Relation(MF, T1,T2, [1:1|1:n | n:n ])  Object methods Update MF Update the two related objects Get the two related objects  Class methods Add and Delete Relation Objects Search by MF Search objects related to a given object

25. DORSDL Workshop - 21 th of September, 2006 25 Aggregation Type A = Aggregation(MF, MF’ + ordering, B) BA(MF) Hidden Relation Type used by Aggregation (MF’ and an ordering number) Object methods  Add, remove object of B from aggregation  Get aggregated objects  Search through aggregated objects: by MF or by ordering Class methods  Add and Delete Aggregation Objects  Search by MF

26. DORSDL Workshop - 21 th of September, 2006 26 Example: Annotations to Articles Articles = Raw(, PDF) Notes = Raw( ) Anns = Relation(Articles, Notes, [n:n]) Applications can  Add&Delete articles, notes, and annotations objects  Given an article object A, reach its notes through Anns.getRelated(A)  Search all notes inserted in a given period through Notes.search(“Date between x an y”) The store can  Create specific indices for each MF format  Create a full-text index for PDFs  Find the best way to compress PDF and the MF formats available

27. DORSDL Workshop - 21 th of September, 2006 27 Towards DL Systems MF mappings: managed by the administrators  Consequences for storage optimization? Behavior management: managed by administrators  Limited to file manipulators or more than that, i.e. Web Services? OAI-PMH publishing, harvesting, and aggregation Store distribution and organization Object navigation  Include objects as values for Metadata Fields?  Query language?

28. DORSDL Workshop - 21 th of September, 2006 28 Towards DL Systems System Interface Typed Repository Service Typed Information Object Model (Type algebra) Application DO1DO2DO3 ArticlesNotesRefs Component on Notes and Refs Component on Articles ANR MF mappingsBehaviors OAI-PMH Publishing – harvesting aggregating

29. DORSDL Workshop - 21 th of September, 2006 29 OpenDLib Repository Service Rich Document Model: DoMDL Repository Service tailored to DoMDL Repository Services  Can be configured to handle objects that respect a specific subset of DoMDL, thanks to T-DoMDL  Export DoMDL information objects

30. DORSDL Workshop - 21 th of September, 2006 30 Light T-DoMDL Coll ::= Name = Vs, Coll | Name = Virtual(Q,Name), Coll |  Vs::= Version(A) | A A ::= Aggregation(T 1,…,T n ) T ::= Raw[file formats] | A

31. DORSDL Workshop - 21 th of September, 2006 31 Conclusions and future issues Experiment  Motivation: Digital Libraries call for Systems  Implementing T-DoMDL in OpenDLib Repository Service Next steps  Support full type algebra  Exploring query languages and storage optimization  Experiment Repository Development Future: towards fully-fledged DL Systems  Preservation  OAI-PMH Harvesting and publishing  User Rights Management (Collections)  More…