OGSA-DQP factory configuration documents

OGSA-DQP factory configuration documents specify information required by a DQP coordinator. This includes the locations of evaluators, OGSA-DAI servers and data resources as well as other coordinator configuration information.

DQP factory configuration document contents

The DQP factory configuration document specifies:

The evaluators which can be used by a DQP coordinator.
The OGSA-DAI relational data resources over which queries can be run.
[Optional] Analysis (Web) services that can be used by a a DQP coordinator.

The DQP factory configuration document is an XML document. It has the XML schema: DQPConfiguration.xsd.

The XML schema allows the following information to be provided. Each of these are provided as child elements of the <DQPConfiguration> element:

The URLs of evaluators to be used by the coordinator. Thare are specified within a <DQPEvaluatorList> element. These are standard OGSA-DAI server URLs:
- For OGSA-DAI Axis they have form http://HOST:PORT/dai/services e.g. http://myhost:8080/dai/services
- For OGSA-DAI GT they have form http://HOST:PORT/wsrf/services/dai e.g. http://myhost:8080/wsrf/services/dai
The URLs and data resource IDs of OGSA-DAI data resources over which queries can be run. These are specified within a <DataResourceList> element.
Computational meta data. This is optional and can be ignored if you do not want to use it. Computational meta data is an advanced DQP option which is described in the page on computational meta data. This is specified within a <DQPMachineList> element.
User-defined functions. This is optional and can be ignored if you do not want to use it. User-defined functions are an advanced DQP option which is described in the page on user-defined functions This is specified within a <UserDefinedFunctionList> element.

Examples

A simple example DQP factory configuration document is as follows:

<DQPConfiguration xmlns="http://uk.org.ogsadai/dqp/configuration">
   <DQPEvaluatorList>		
      <EvaluatorURI>http://rpc122.cs.man.ac.uk:8081/dqp-evaluator/services/QueryEvaluationService</EvaluatorURI>
   </DQPEvaluatorList>
   <DataResourceList>
      <ImportedDataSource>		
         <URI>http://rpc122.cs.man.ac.uk:8080/wsrf/services/dai</URI>
         <ResourceID>goterms</ResourceID>  
      </ImportedDataSource>		
      <ImportedDataSource>	
         <URI>http://rimside.ncl.ac.uk:8080/wsrf/services/dai</URI>
         <ResourceID>gims</ResourceID>  
      </ImportedDataSource>		
   </DataResourceList>		
</DQPConfiguration>

This example specifies one evaluator and two OGSA-DAI relational data resources exposed by two different OGSA-DAI servers.

A more complex example DQP factory configuration document is as follows:

<DQPConfiguration xmlns="http://uk.org.ogsadai/dqp/configuration">
   <DQPEvaluatorList>		
      <EvaluatorURI>http://rpc122.cs.man.ac.uk:8081/dqp-evaluator/services/QueryEvaluationService</EvaluatorURI>
      <EvaluatorURI>http://rimside.ncl.ac.uk:8081/dqp-evaluator/services/QueryEvaluationService</EvaluatorURI>
   </DQPEvaluatorList>
   <DataResourceList>
      <ImportedDataSource>		
         <URI>http://rpc122.cs.man.ac.uk:8080/wsrf/services/dai</URI>
         <ResourceID>goterms</ResourceID>  
      </ImportedDataSource>		
      <ImportedDataSource>	
         <URI>http://rimside.ncl.ac.uk:8080/wsrf/services/dai</URI>
         <ResourceID>gims</ResourceID>  
      </ImportedDataSource>		
      <ImportedService name="Entropy" wsdlURL="http://pc01.ast.ac.uk:8080/services/EntropyAnalyserService?wsdl"/>
   </DataResourceList>		
</DQPConfiguration>

This example specifies two evaluators, two OGSA-DAI relational data resources exposed by two different OGSA-DAI servers and an analysis service.

Important checks

When writing a DQP factory configuration document take care to ensure that:

The XML is valid and the XML element names are correct.
That URLs are correct - both their host names and port numbers - and that these services have actually been deployed and are available. This applies to the evaluators, the OGSA-DAI servers which expose the data resources and any imported analysis services.
That data resource IDs are correct - that these are known to the associated OGSA-DAI services and have been configured correctly and can be used.

Who provides the DQP factory configuration document?

A coordinator can be configured to use DQP factory configuration documents when the DQP coordinator is deployed. This allows the coordinator to have access to a default configuration if the client does not provide one. This is termed factory configuration.

Alternatively, the DQP coordinator can be configured with an empty DQP factory configuration document in which case the client has to provide one. This is termed client configuration.

Or, a mix of both approaches can be used.

Consider the following DQP factory configuration file which an OGSA-DQP deployer may have used to provide the default configuration for their coordinator:

<DQPConfiguration xmlns="http://uk.org.ogsadai/dqp/configuration">
   <DQPEvaluatorList>		
      <EvaluatorURI>http://rpc122.cs.man.ac.uk:8081/dqp-evaluator/services/QueryEvaluationService</EvaluatorURI>
      <EvaluatorURI>http://rimside.ncl.ac.uk:8081/dqp-evaluator/services/QueryEvaluationService</EvaluatorURI>
   </DQPEvaluatorList>
   <DataResourceList>
      <ImportedDataSource>		
         <URI>http://rpc122.cs.man.ac.uk:8080/wsrf/services/dai</URI>
         <ResourceID>goterms</ResourceID>  
      </ImportedDataSource>		
      <ImportedDataSource>	
         <URI>http://rimside.ncl.ac.uk:8080/wsrf/services/dai</URI>
         <ResourceID>gims</ResourceID>  
      </ImportedDataSource>		
      <ImportedService name="Entropy" wsdlURL="http://pc01.ast.ac.uk:8080/services/EntropyAnalyserService?wsdl"/>
   </DataResourceList>		
</DQPConfiguration>

The client can add another evaluator by submitting the document:

<DQPConfiguration xmlns="http://uk.org.ogsadai/dqp/configuration">
   <DQPEvaluatorList>		
      <EvaluatorURI>http://rpc122.cs.man.ac.uk:8081/dqp-evaluator/services/QueryEvaluationService</EvaluatorURI>
      <EvaluatorURI>http://rimside.ncl.ac.uk:8081/dqp-evaluator/services/QueryEvaluationService</EvaluatorURI>
      <EvaluatorURI>http://rpc111.cs.man.ac.uk:8081/dqp-evaluator/services/QueryEvaluationService</EvaluatorURI>
   </DQPEvaluatorList>	
</DQPConfiguration>

Note that the client has to provide all three - there is no "smart" combination of the evaluator information in the default configuration and that provided by the client, as we now explain...

Which configuration takes precedence - the default configuration or the one provided by the client?

If the client provides a document that specifies a list of evaluators then this is used instead of those in the coordinator's default configuration document.

If the client provides a document that specifies a list of OGSA-DAI services and data resources then this is used instead of those in the coordinator's default configuration document.

A client can provide a document that specifies both evaluators and OGSA-DAI services and data resources, or just evaluators, or just OGSA-DAI services and data resources.

However, it must be ensured that

At least one evaluator service is specified - so if the DQP coordinator's default configuration does not specify one then the client must.
At least one OGSA-DAI service and data resource is specified - so if the DQP coordinator's default configuration does not specify one then the client must.

If these conditions are not met then the creation of a new DQP resource by the DQP factory will fail.

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