1	Identifiers Module 5 Min-Yen KAN *Based on William Arms presentation at Cornell Univ. Modified by permission
2	You see this everyday…
3	Desirable Properties of Identifiers Location independent name Globally unique Persistent across time Choice of human generated or automatic generation Fast resolution Decentralized administration Supported from standard user interfaces
4	Identifier systems We’ll look at several different systems today URN PURL DOI OpenURL
5	Uniform Resource Names (URN) Globally unique, persistent, and accessible over the network Persistence: That is, the URN will be globally unique forever. Scalability: URNs can be assigned to any resource Legacy / Extensible: Backward and forward compatible Some Examples: urn:hdl:cnri.dlib/august95 urn:lifn:some.domain:anything-goes-here urn:path:/A/B/C/doc.html urn:inet:library.bigstate.edu:aj17-mcc
6	Persistent URLs http://purl.org/ PURL is a normal URL Implement a layer of indirection Uses standard HTTP redirect Simple model
7	More details on PURL Partial redirection http://purl.org/kanmy/pictures/nus.jpg http://www.comp.nus.edu.sg/~kanmy/ pictures/nus.jpg A PURL with no associated indirection causes the PURL resolver to generate a history page Private and universal indirection with access control
8	PURL Issues Places the burden of resolution on the manager of information PURL resolvers don’t know about each other: federated, no centralized registry If URL goes down, doesn’t force or notify maintainer Doesn’t guarantee that document will be available, indirection can lead to a 404
9	Examples of DOIs
10	Hierarchy of Naming Authorities
11	Address Rules The Global Handle Service stores: a record for each naming authority a record for each local handle service The record for each naming authority includes: the home handle service for that naming authority For each handle, the home handle service stores: the handle record
12	Multiple Resolution Leave the resolution up to the client Return all DOI data to the client
13	DOIs in action
14	Flexibility
15	Reorganization by Publisher
16	Catalogs and Indices
17	Multiple Copies
18	The General Model
19	DOI Summary Uses multiple levels of indirection ___________________ But also more complicated, ___________________ Supported by consortium of publishers (big and small)
20	OpenURL A identifier system that takes user’s context into account Created to solve the ________________________
21	"Different providers use different URL..." Different providers use different URL and points of access to the data
22	Indirection in OpenURL Dissociate document from vendor-, library-specific provisions OpenURL lists access metadata
23	Input: OpenURL Example Moll JR, Olive & M, Vinson C. Attractive interhelical electrostatic interactions in the proline- and acidic-rich region (PAR) leucine zipper subfamily preclude heterodimerization with other basic leucine zipper subfamilies. J Biol Chem. 2000 Nov 3 ; 275(44):34826-32. doi:10.1074/jbc.M004545200 http://sfx1.exlibris-usa.com/demo?sid=ebsco:medline&aulast=Moll&auinit=JR&date= 2000-11-03&stitle=J%20Biol%20Chem&volume=275&issue=44&spage=34826 http://sfxserv.rug.ac.be:8888/rug?id=doi:10.1074/jbc.M004545200 Legend: red - BASE-URL of service component blue - identifier of the resource where the user clicks the OpenURL, added by publisher’s rewrite grey - metadata and identifiers DOI can be used to resolve the actual content
24	OpenURL Issues Service component gets metadata query information Access and use information goes to library, not to publisher Not just user-to-user, but for generalized dynamic linking Web page to journal article full-text Abstract to library catalog collection Currently requires publishers to recast URLs as OpenURLs
25	Summary PURLs _________________ ___________________ DOI ____________________ Purpose: ________________ Resolution to multiple items of current state data Notably including location(s) and metadata OpenURL Purpose: _________________ Selects between multiple items returned by DOI
26	The Wayback Machine Title IIC gives LoC rights to every book published Legal deposit simulated on the web by folks at the Internet Archives http://www.archive.org/web/web.php
27	To think about How do these systems guarantee permanence? (hint: they don’t)
28	References URN: http://www.w3.org/Addressing/ PURL: http://www.purl.org/ DOI: http://www.doi.org/ openURL: http://www.sfxit.com/open/index.html Internet Archives: http://www.archive.org/web/web.php