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Z39.50 as a Web Service

Z39.50 as a Web Service. Ralph LeVan Research Scientist. Roadmap. Why Z39.50 as a Web Service? The Weaknesses of Classic Z39.50 The Strengths of Classic Z39.50 SRW: Search and Retrieve on the Web SRU: Search and Retrieve with URL’s Outlook for SRW/SRU. The Weaknesses of Classic Z39.50.

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Z39.50 as a Web Service

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  1. Z39.50 as a Web Service Ralph LeVan Research Scientist

  2. Roadmap • Why Z39.50 as a Web Service? • The Weaknesses of Classic Z39.50 • The Strengths of Classic Z39.50 • SRW: Search and Retrieve on the Web • SRU: Search and Retrieve with URL’s • Outlook for SRW/SRU

  3. The Weaknesses of Classic Z39.50 • Not popular with the Web community • Connection-based Sessions • Binary Encoding • Transmitted directly over TCP/IP • Complicated

  4. Z39.50 Complicated? • 11 Native Services • Init, Search, Present, DeleteResultSet, AccessControl, ResourceControl, TriggerResourceControl, ResourceReport, Scan, Sort, Segment. • 7 Extended Services • PersistentResultSet, PersistentQuery, PeriodicQuerySchedule, ItemOrder, DatabaseUpdate, ExportSpecification, ExportInvocation

  5. Z39.50 Complicated? • 156 page standard • 147 in the 2002 draft • Vocabulary from the OSI community • Target, Origin, APDU, A-association, Z-association.. • Records described with ASN.1 • Attribute Sets

  6. The Strengths of Classic Z39.50 • Result Sets (a.k.a. Statefulness) • Abstraction • Abstract Access Points (Attribute Sets) • Abstract Record Schemas • Explain

  7. SRW: Search and Retrieve on the Web • SOAP (Simple Object Access Protocol) Based • HTTP • XML • Records Described in WSDL (Web Service Description Language) • 1 Service: SearchAndRetrieve • No Documentation :-)

  8. Semantically equivalent to classic Z39.50 • Gateways Trivial • Preserves the experience of the ZIG without the baggage of the standard • Syntactic equivalence discounted

  9. SRW: The Basics • Only one database per request • String (not structure) based queries • Index Sets, not Attribute Sets • One Record Syntax (XML)

  10. The SRW Request • String Query • Integer StartRecord • Integer MaximumRecords • String RecordSchema

  11. The SRW Response • String ResultSetReference • ResultSetName • ResultSetTimeToLive • Integer TotalHits • Records • Status (Status Code & Diagnostic)

  12. CQL: Common Query Language • Loosely based on CCL Search • Boolean & Proximity Operators • Index Sets & Indexes • Truncation Characters ‘*’, ‘#’ & ‘?’ • Example: dc.title=“harry potter” or bib1.isbn=123-456-78x

  13. Explain Now Possible • Not practical for classic Z39.50 • List of supported Schemas • List of supported Indexes

  14. SRU: Search and Retrieve with URL’s • SRW Without the SOAP Wrapper • Intended for Thin Clients • Adds ResponseSchema Parameter • Example http://deimos.oclc.org/SRW/etdcat?query=nuclear&maxRecords=10

  15. Outlook for SRW/SRU • A solution looking for a problem? • Not likely to be quickly adopted by the library community • Could show up first in other communities: Geospatial, Biodiversity, OAI(?) • Will be seen as a competitor with XML Query

  16. Links • http://www.loc.gov/z3950/agency/zing/zing.html • http://staff.oclc.org/~levan/docs/RAC20020321-SRW.ppt

  17. & Questions nswers A

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