1. William Y. Arms Corporation for National Research Initiatives March 22, 1999 Object models, overlay journals, and virtual collections

2. William Y. Arms Department of Computer Science, Cornell University March 22, 1999 Object models, overlay journals, and virtual collections

3. William Y. Arms Corporation for National Research Initiatives March 22, 1999 Object models, overlay journals, and virtual collections

4. Physical and Logical Views of Information Physical view: Data structures, files, directories, servers Publishers, libraries, web sites Logical view: Works, expressions, manifestations, items Object models (document models) Overlay journals Virtual collections

5. What is Content? Works, expressions, manifestations, items

6. Work The underlying abstraction. Examples Homer's The Iliad. Beethoven's Fifth Symphony. The Unix operating system.

7. Expression A work is realized through an expression. Examples The Iliad was first expressed orally, then it was written down as a fixed sequence of words. Beethoven's Fifth Symphony can be expressed as a printed score or by any one of many performances. The Unix operating system has separate expressions as source code and machine code.

8. Works and Expressions Works and Expression Many works are realized through a single expression. Examples The poem, The Road Not Taken by Robert Frost. The picture: In such examples, there is no practical distinction between expression and work.

9. Manifestations Manifestation A expression is given form in one or more manifestations. Examples The text of The Iliad has been manifest in numerous manuscripts and printed books. A musical performance can be distributed on CD, or broadcast on television. Software is manifest as files, which may be stored or transmitted in any digital medium.

10. Items Item When many copies are made of a manifestation, each is a separate item. Examples A specific copy of a book. A copy of a computer file.

11. Object Models

12. Beyond Simple Documents Many digital objects are more than static files of data. Dynamic objects: What is presented to the user depends upon the execution of computer programs or other external activities. Complex objects: Objects are made up from many inter-related elements. Alternate disseminations: Digital objects may offer the user a choice of access methods. Databases: A database comprises many alternative records, with different records selected each time the database is accessed.

13. Object Models and Structural Types Web object Digitized materials Digitized image Set of digitized page images Marked-up text with page images Digitized audio recording Sets Set of digital objects Searchable set of digital objects

14. Web Object: File with URL & Data Type Identifier Data Metadata http://www.dlib.org/boats/swan56 jpg

15. Object Model: Digitized Image Data Several manifestations: thumbnail image reference image archival image Metadata Each manifestations may have its own metadata

16. Object Model: Digitized Image Identifier Data Metadata archive jpg hdl:loc.ndlp/amrlp.1234567 thumbnail gif reference jpg object metadata

17. Object Model: Set of Digitized Page Images Data Each page: separate image Metadata Structure of work: page sequence page numbers special pages

18. Object Model: Set of Digitized Page Images Identifier Data Metadata page 3 gif hdl:loc.ndlp/amrlp.13579 page 1 gif page 2 gif page map

19. Page Map List of pages Numbers printed on pages Blocking of information on pages (columns, figures) Sequences of information across pages A page map relates the page images to the structure of the information, e.g.: A page map is metadata for a specific manifestation

20. Overlay Journals and Virtual Collections Logical organization of physically separate works

21. The NSF SMETE Library Soon, all scientific and engineering information will be available on-line: Journals, reports, papers, standards, patents Data sets, instruments, sensors Computer programs, simulations, designs Maps, images, films... etc., etc., etc.

22. The Instructor's Wish List To discover materials and services: Good science Comprehensible to students -- effective for teaching Stable -- will not change or disappear Access to collections and services that are provided by many independent organizations: No uniform catalog or index to everything Mixture of for-profit and open access information

23. The Instructor's Wish List To discover materials and services: Good science Comprehensible to students -- effective for teaching Stable -- will not change or disappear Access to collections and services that are provided by many independent organizations: No uniform catalog or index to everything Mixture of for-profit and open access information

24. Conventional Journal Contents Articles

25. Overlay Journal Contents Articles in Repository A Articles in Repository B

26. Overlay Journals Contents of Journal I Articles in Repository A Articles in Repository B Contents of Journal II

27. Overlay Journals with Preprint Servers Contents of Journal I Research Web site Preprint server Contents of Journal II CoRR Cornell CS Reports

28. NCSTRL User CSTR ACM CoRR D-Lib SMETE Library: Physical Sites

29. SMETE Library: Virtual Collections SMETE Links show the members of the virtual collection

30. Metadata for Virtual Collections Reference linking Identifiers (URLs, URNs,...) Citations and reverse citations Information discovery Cataloguing and indexing Object models Structural types Disseminators

31. Indexing and Cataloguing Conventional cataloguing and indexing: Skilled professionals, following quality guidelines. Web spiders and gatherers: Programs that gather information and build indexes (e.g., Infoseek, Harvest). Meta-data in publishing: Addition of metadata by the creator to aid automatic indexing (e.g., Dublin Core). Content extraction: Indexing using structured text, speech recognition, or image content.

32. The End Physical view: Data structures, files, directories, servers Publishers, libraries, web sites Logical view: Works, expressions, manifestations, items Object models (document models) Overlay journals Virtual collections