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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 • Not popular with the Web community – Connection-based Sessions – Binary Encoding – Transmitted directly over TCP/IP • Complicated 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 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 The Strengths of Classic Z39.50 • Result Sets (a.k.a. Statefulness) • Abstraction – Abstract Access Points (Attribute Sets) – Abstract Record Schemas • Explain 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 :-) Semantically equivalent to classic Z39.50 • Gateways Trivial • Preserves the experience of the ZIG without the baggage of the standard • Syntactic equivalence discounted SRW: The Basics • Only one database per request • String (not structure) based queries • Index Sets, not Attribute Sets • One Record Syntax (XML) The SRW Request • String Query • Integer StartRecord • Integer MaximumRecords • String RecordSchema The SRW Response • String ResultSetReference – ResultSetName – ResultSetTimeToLive • Integer TotalHits • Records • Status (Status Code & Diagnostic) 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 Explain Now Possible • Not practical for classic Z39.50 • List of supported Schemas • List of supported Indexes 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 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: MetaSearch, Geospatial, Biodiversity, OAI(?) • Will be seen as a competitor with XML Query Links • http://www.loc.gov/z3950/agency/zing/zing. html • http://staff.oclc.org/~levan/docs/SRWRAC20030814.ppt Questions nswers A