Download 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
• 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