Manifestations

• Z39.50-1988

• ISO TC46/WG4/SC4 10162/3 SR

• Z39.50-1992

• Z39.50-1995

• Z39.50-1988 “Future Services”

• Z39.50-1992 “Future Service”

• Z39.50-1995 “Facility”

Z39.50-1988 Foreword“Future Services”

• List Databases

• List Access Points

• List Elements

• List Element Set

• List Element Sets

Z39.50-1992 Foreword“Future Services”

• Explain– to allow an origin to obtain details of the target

implementation, including databases available for searching, data elements in records of a specified database, element sets supported, elements within a specified element set, attribute sets supported, attributes supported within a supported attribute set, diagnostic sets, and record syntaxes.

Z39.50-1995 “Explain Facility”

• Explain database– IR-Explain-1

• accessed via Z39.50 Search and Present services

• Explain Attribute set– exp-1

• Explain syntax

• Z39.50-1988

• ISO TC46/WG4/SC4 10162/3 SR

• Z39.50-1992

• z39.50-1995

Contributors

• Makx Dekkers• Liv Holm• Cliff Lynch• Mark Needleman• Bob Waldstein• Mark Hinnebusch• Denis Lynch• Ray Denenberg

Rationale (Denis Lynch 1997)

• Many clients don’t know their servers– Users point clients at new servers– Servers add or change databases & services

• Clients need dynamic information– Server hours of operation– Billing rates– Supported attribute combinations– Field labels

Target Info (D. Lynch)

• One TargetInfo record per server– Target name – database combinations– Message of the day– Contact and access information– Network addresses

Database Info

• One DatabaseInfo record per database– Database name– Databases that can be searched with this one– Databases that are subsets of this one– Attribute sets, syntaxes, schemas, query types...– Copyright and contact information

• TagSetInfo – all tags defined in a tagset

• SchemaInfo – Mapping of tagset numbers to tagsets– The record structure

• RecordSyntaxInfo – describes the record structure

• AttributeSetInfo – lists every attribute

• Attribute Details– May list patterns for legal combinations {

{ { Use, {4, 16, 24} }, { Structure, All } }, { { Use, 1001 }, { Structure, 2 } }}

Term Lists

• One TermListInfo per database, – lists “indexes”– link to TermListDetails– A title, for display to users– A search cost hint (optimized, expensive…)– Is it scannable

• TermListDetails

Term Lists

• TermListDetails: may apply to many databases– Attribute combinations that access this term list– More info about scanning– Sample terms

Element Specification

• ElementSetDetails for Element Set Names

• RetrievalRecordDetails for CompSpec– Mapping of schema elements to record

elements

Sort Information

• Sort keys available for database

• Map of elements and attributes

Extended Services

• Supported services– Availability, cost…– Is package retained in ES database?– Can ES be executed synchronously?

Category List

• Explain categories supported– Dynamically discover what can be dynamically

discovered

Miscellaneous Complexities

• AccessInfo

• TermList titles for access points Or Use attributes from AttributeCombinations

• AssociatedDBs

• SubDBs supports “more specific” function

• PerElementDetails for field labels

• ProcessingInformation

Issues

• Model – Search and retrieve from a Z39.50 database

• Complexities

• What Information does a client need?