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Key Standards Update: SRU (“Technical” Details). Dr. Robert Sanderson Dept. of Computer Science University of Liverpool CNI, 4th April 2006 Slide 1. Overview.

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Key Standards Update:

SRU (“Technical” Details)

Dr. Robert Sanderson

Dept. of Computer Science

University of Liverpool

CNI, 4th April 2006 Slide 1


Aims and Motivations

Other Protocols: OAI, OpenSearch

Response Format Additions



Extensions, Diagnostics

CNI, 4th April 2006 Slide 2


Overall aims/goals for the changes towards SRU 1.2

Reduce protocol complexity without losing important features

Allow easier/deeper integration with other protocols

Correct past mistakes (mea culpa!)

Improve visibility, understanding and implementations

Escape the “library ghetto”

... Profit!

CNI, 4th April 2006 Slide 3

Ease of Integration

  • Other protocols to interoperate with:

    • Open Archives Initiative (OAI-PMH)

    • OpenSearch

    • OpenURL

    • “Web 2.0” / “Library 2.0” enabling techniques

  • (Should change name to “OpenSRU 2.0” ??)

  • CNI, 4th April 2006 Slide 4

    Ease of Integration: OAI

    Formalize a profile to allow OAI to be implemented over SRU

    rec.identifier Search by identifier

    rec.lastModificationDate Search by modification time

    rec.collectionIdentifier Search by 'set'

    Plus extension to allow OAI header information to be returned (record is in which sets, etc)

    CNI, 4th April 2006 Slide 5

    Ease of Integration: OpenSearch

    SRU compatible profile of OpenSearch

    OpenSearch allows the server to pick the names of parameters ... Pick names that match SRU's parameters

    Allow query extensions to build CQL from OpenSearch's parameters. x-dc-title=Lord of the Rings&x-dc-creator=Tolkien

    Unaware SRU and OS servers will just ignore.

    CNI, 4th April 2006 Slide 6

    Response Format Additions

    Allow record Identifier (metadata level) to be returned in the record structure

    Allow the full base URL to be returned in the response (within echoedRequest)





    <recordData> ... </recordData>







    CNI, 4th April 2006 Slide 7


    Sort has been a bugbear since version 1.0

    Extend CQL to include sorting specification

    Allow use of indexes with modifiers to specify semantics

    (Previously XPath expressions)

    CQL parsers can be used to parse both, reducing workload (assuming that an existing CQL parser is used)

    Enhances independence of CQL as query languageExample: dc.title any fish sortBy dc.creator

    CNI, 4th April 2006 Slide 8


    One of the most complicated parts of SRU/CQL

    No easy solution, but some improvements...

    Recommendations for how to extend proximity modifiers -- Use a new context set for modifiers

    Explainable server defaults for proximity modifiers

    Improved documentation

    Agreement to not agree on anything further until the OASIS Technical Committee to include other interested parties

    CNI, 4th April 2006 Slide 9

    Extensions, Diagnostics

    • Issue: Number of matching records may be unknown or approximate, no way to notify this condition

    • New diagnostics:

      • Number of records approximate

      • Number of records truncated

  • Request Extension:

    • Approximate record count is acceptable

  • CNI, 4th April 2006 Slide 10

    Extra Term Information

    Issue: Desirable to return sub-query level details Eg: How many records matched in one part of the query

    Details to return need to be extensible

    Solution: Add extraTermInfo into the XCQL representation to be returned in the response

    Some general extensions will be defined, but allows implementors to include any information they think appropriate

    Needs a parameter to request that the details be returned (like all SRU extensions)

    CNI, 4th April 2006 Slide 11

    Thank you!

    • Questions?

    CNI, 4th April 2006 Slide 12