1. Digital Object Prototypes An Effective Realization of Digital Object Types K. Saidis 1, G. Pyrounakis 2, M. Nikolaidou 2, A. Delis 1 1 Department of Informatics And Telecommunications 2 Libraries Computer Center University of Athens 10 th European Conference on Research and Advanced Technology for Digital Libraries

2. September 18, 2006 - Alicante, Spain2 Outline The problem: Develop an integrated web-based DL that manages diverse & heterogeneous digital material in a unified manner Our proposed solution: Digital Object Prototypes – an effective realization of Digital Object (DO) types DOPs Overview Discussion

3. September 18, 2006 - Alicante, Spain3 Pergamos: Un. of Athens DL Over 1 million objects originating from 8 disparate collections Heterogeneous, digitised material requiring detailed cataloguing Motivation Simplify & speed up cataloguing Decrease development time Avoid custom coding for handling variations of digital material

4. September 18, 2006 - Alicante, Spain4 Digital Objects Human generated artifacts comprised of 4 components: metadata, digital content, relationships & behaviors Several ways to encode them: METS, FOXML, RDF, MPEG-21 Diverse kinds of material are represented using variations of DO components

5. September 18, 2006 - Alicante, Spain5 The problem DOs (e.g. books, papers, photos etc) should be treated in a manner that reflects the nature of the underlying “real-world” objects DL systems do not capture, express or use the nature of DOs effectively: DL users are forced to deal with each object’s idiosyncrasies manually

6. September 18, 2006 - Alicante, Spain6 Digital Object Prototypes Introduced in last year’s ECDL A Digital Object Prototype (DOP) is a DO Type specification, providing a detailed definition of a DO’s constituent parts: metadata, files, relationships and behaviors With the use of DOPs, high level services can handle DO component variations in a uniform manner

7. September 18, 2006 - Alicante, Spain7 DOPs Contd. DOPs provide the means to generate user-defined types of digital objects DO type conformance: DOs automatically conform to their respective DOP Inexpensive to add new types of digital material or modify existing ones (no custom coding required)

8. September 18, 2006 - Alicante, Spain8 DOPs Contd. DOPs draw on the notions of the OO model to implement DO types All objects have a type Objects honor encapsulation Inheritance (under development) DOs are conceived as instances of their respective prototype Stored DOs are treated as serializations of DO instances

9. September 18, 2006 - Alicante, Spain9 A DO Instance

10. September 18, 2006 - Alicante, Spain10 Instantiation / Serialization

11. September 18, 2006 - Alicante, Spain11 DOPs 3-tier DL Architecture Composition of DO behaviors DO Typing & Instantiation Storage

12. September 18, 2006 - Alicante, Spain12 A DOP specifies Metadata element sets File types / conversions / batch ingestions Permitted relationships Private & Public behaviors

13. September 18, 2006 - Alicante, Spain13 Behaviors Encapsulation: Private & Public behaviors Private behaviors are executed by the DO instance “behind the scenes” (the object itself triggers selected functionality) Public behaviors are exposed to clients (clients trigger selected functionality)

14. September 18, 2006 - Alicante, Spain14 Metadata Specification DOPs specify: the metadata element sets used by all objects of this type the individual elements (fields) that constitute each set possible mappings among elements of these sets

15. September 18, 2006 - Alicante, Spain15 Metadata Specification II Automatic loading / serialization of metadata sets Behavioral characteristics of metadata elements: isMandatory, isHidden, isRepeatable, defaultValue, validation facilitate services to adjust to the object’s requirements Mappings are automatically applied by the DO instance

16. September 18, 2006 - Alicante, Spain16 Files Specification DOPs specify: The permitted files and their allowed formats The information required to convert files from one format to another Batch file ingestion / automatic DO creation process for each file

17. September 18, 2006 - Alicante, Spain17 Example Historical Archive’s Senate Session Proceedings > Folders > Sessions > Pages What is a Page DO: A digital image stored in various formats (e.g. high quality TIFF, web quality JPEG, thumbnail) What is a Session DO: A complex DO, consisting of Page DOs and session proceedings metadata

18. September 18, 2006 - Alicante, Spain18 Example Contd. Automatic file conversions Page DOs automatically generate the two derivate formats from the high quality image Batch Content Ingestion / DO Creation Session DOs generate Page DOs from zip files containing high quality images

19. September 18, 2006 - Alicante, Spain19 Session DOP

20. September 18, 2006 - Alicante, Spain20 Page DOP

21. September 18, 2006 - Alicante, Spain21 Relationships DOPs specify: The structural relationships the objects are allowed to participate in (e.g. child- of, or is-parent-of) Whether the objects are allowed to reference other entities, either internal (residing in the same DL) or external ones

22. September 18, 2006 - Alicante, Spain22 DOPs and Collections DOPs “live” in the context of a collection (collection pertinent scope) Collections are represented in terms of “special-purpose” DOs Collections may contain other collections (hierarchical namespace) The Digital Library is the collection of all collections

23. September 18, 2006 - Alicante, Spain23 Pergamos Collections & DOPs CollectionSub collectionsDOPs dltheatre, papyri, medical, folklore, histarch - dl.theatre-album, photo dl.papyripapyrus dl.medical-image dl.folklore-notebook, chapter, page dl.histarchsenate- dl.histarch.senateprocs- dl.histarch.senate.procs-folder, session, page

24. September 18, 2006 - Alicante, Spain24 A hierarchy of DO instances

25. September 18, 2006 - Alicante, Spain25 dl.histarch.* DOPs DOPMetadataFilesRelations folder- Qualified DC - EAD-like - EAD to DC mappings none - contains session or page session - Qualified DC - EAD-like - EAD to DC mappings zip-contains page pagenone - HQ image - Web image - Thumbnail

26. September 18, 2006 - Alicante, Spain26 dl.folklore.* DOPs DOPMetadataFilesRelations notebook- Qualified DCnone - contains chapter or page chapter - Qualified DCzip-contains page pagenone - HQ image - Web image - Thumbnail

27. September 18, 2006 - Alicante, Spain27 dl.papyri.* DOPs DOPMetadataFilesRelations papyrusQualified DC - Original Image - Processed image - Web image - Thumbnail none

28. September 18, 2006 - Alicante, Spain28 dl.theatre.* DOPs DOPMetadataFilesRelations album - Custom (theatrical play metadata) - DC - Custom to DC mappings nonecontains photo photoQualified DC - Original Image - Web image - Thumbnail none

29. September 18, 2006 - Alicante, Spain29 Summary We argue that digital objects do have types (they fall into categories with uniform characteristics and behavior) First realization of DO Type conformance: DOs honor the specifications residing in their DOP automatically Effective management of diverse digital material: the DL system interprets DO types, not the user

30. September 18, 2006 - Alicante, Spain30 Future Work Implementation of DOPs inheritance (reuse: new types can be derived from existing ones) Offline DOP validation process Make DOPs operate independently of the underlying repository Open source release of the DOPs framework

31. September 18, 2006 - Alicante, Spain31 Thank you Questions? Email: saiko@di.uoa.grsaiko@di.uoa.gr DOPs in action: Pergamos demo tomorrow (Poster #17)