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Key Standards Update: SRU (“Technical” Details). Dr. Robert Sanderson Dept. of Computer Science University of Liverpool [email protected] 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

[email protected]

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