Z39.50 as a Web Service

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Z39.50 as a Web Service

• Ralph LeVan
• Research Scientist

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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 URLs
• Outlook for SRW/SRU

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The Weaknesses of Classic Z39.50

• Not popular with the Web community
• Connection-based Sessions
• Binary Encoding
• Transmitted directly over TCP/IP
• Complicated

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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

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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

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The Strengths of Classic Z39.50

• Result Sets (a.k.a. Statefulness)
• Abstraction
• Abstract Access Points (Attribute Sets)
• Abstract Record Schemas
• Explain

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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 -)

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Semantically equivalent to classic Z39.50

• Gateways Trivial
• Preserves the experience of the ZIG without the
  baggage of the standard
• Syntactic equivalence discounted

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SRW The Basics

• Only one database per request
• String (not structure) based queries
• Index Sets, not Attribute Sets
• One Record Syntax (XML)

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The SRW Request

• String Query
• Integer StartRecord
• Integer MaximumRecords
• String RecordSchema

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The SRW Response

• String ResultSetReference
• ResultSetName
• ResultSetTimeToLive
• Integer TotalHits
• Records
• Status (Status Code Diagnostic)

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CQL Common Query Language

• Loosely based on CCL Search
• Boolean Proximity Operators
• Index Sets Indexes
• Truncation Characters , ?
• Example
• dc.titleharry potter or bib1.isbn123-456-78x

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Explain Now Possible

• Not practical for classic Z39.50
• List of supported Schemas
• List of supported Indexes

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SRU Search and Retrieve with URLs

• SRW Without the SOAP Wrapper
• Intended for Thin Clients
• Adds ResponseSchema Parameter
• Example
• http//deimos.oclc.org/SRW/etdcat?querynuclearma
  xRecords10

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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

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Links

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

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Questions

nswers
A