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The DAIS-WG Specifications
Norman Paton
University of Manchester
(DAIS-WG Co-Chair)
© 2005 Global Grid Forum
The information contained herein is subject to change without notice
DAIS Specifications
• A consistent set of interfaces to access data
resources.
• Partial virtualization/abstraction of the data
resource:
– Still need to know type of underlying data resource.
– Data resource accessed using existing query language.
Specification Documents
• Web Services Data Access and Integration – The Core (WSDAI) Specification, Version 1.0
http://forge.gridforum.org/tracker/index.php?aid=1711
• Web Services Data Access and Integration – The Relational
Realisation (WS-DAIR) Specification, Version 1.0
http://forge.gridforum.org/tracker/index.php?aid=1712
• Web Services Data Access and Integration – The XML
Realization
http://forge.gridforum.org/tracker/index.php?aid=1713
• Current status:
– Recently completed Public Comment Period.
WS-DAI Specifications as Part of Data Profile
WS-DAI
Sets general pattern for
realisations
Extensions for specific
kinds of data resource
WS-DAIR
WS-DAIX
Relational
SQL
XML
XQuery/XPath
Possible Future Realisations
Interface types
• Uses a classification of interface types:
– Originally postulated in the OGSA Data Services document.
–
http://forge.gridforum.org/projects/dais-wg/document/OGSA_Data_Services-ggf10/en/.
• Data description:
– Provides properties that characterise the behaviour provided.
• Data access:
– Provides access to data through a service interface.
• Data factory:
– Provides service interface for the creation of derived data resources.
WS-DAI Specification
• Defines:
– Some base messages/operations:
• Retrieve a property document.
• Destroy relationship between a data service and a data resource.
• Perform generic query.
– Some base message exchange patterns for realisations to use.
– Some resource-type-independent properties.
Data description
• Elements in a properties document,
extended in realisations.
• Some may require explanation:
– DatasetMap: allows different return
types to be supported.
– ConfigurationMap: configures data
resources resulting from factory
messages.
DataResourceAbstractName
ParentDataResource
DataResourceManagement
ConcurrentAccess
DatasetMap
ConfigurationMap
LanguageMap
DataResourceDescription
Readable
Writeable
TransactionInitiation
TransactionIsolation
ChildSensitiveToParent
ParentSensitiveToChild
WS-DAI
Data description – relational extensions
CIMDescription
SQLPropertyDocument
DataResourceAbstractName
ParentDataResource
DataResourceManagement
ConcurrentAccess
DatasetMap
ConfigurationMap
LanguageMap
DataResourceDescription
Readable
Writeable
TransactionInitiation
TransactionIsolation
ChildSensitiveToParent
ParentSensitiveToChild
WS-DAI
SQLResponseItem
SQLResponseItemSequenceNumber
SQLResponseItemName
NumberOfSQLRowSets
NumberOfSQLUpdateCounts
NumberOfSQLReturnValues
NumberOfSQLOutputParameters
NumberOfSQLCommunicationsAreas
SQLResponsePropertyDocument
RowSchema
NumberOfRows
RowsetPropertyDocument
Direct Access
Consumer
SQLExecute (
SQLExecuteRequest (
DataResourceAbstractName,
DatasetFormatURI,
SQLExpression,
SQLExpressionParameters))
Database
Data Service
RelationalDescription
Readable, Writeable, etc
Relational Schema, etc
SQLAccess
SQLExecuteResponse (
SQLRowSet, SQLUpdateCount,
SQLReturnValue,
SQLOutputParameter,
SQLCommunicationsArea)
Relational
Database
Indirect Access
Consumer
SQLExecuteFactory (
Relational
SQLExecuteFactoryRequest (
DataResourceAbstractName,
PortTypeQName,
Data Service
SQLAccessDescription
……, etc
ConfigurationDocument,
SQLExpression))
Relational
SQLAccessFactory
Database
SQLExecuteFactoryResponse (
Reference (SQLResponseAccess))
SQLResponse
Consumer
SQLRowsetFactory(
SQLRowsetFactoryRequest(
DataResourceAbstractName,
portTypeQName,
ConfigurationDocument, Count))
Data Service
SQLResponseDescription
……, etc
SQLResponseFactory
SQLRowSet
SQLRowSetSelectionFactoryResponse
(Reference ( SQLRowSetAccess))
RowSet
Consumer
GetTuples ( GetTuplesRequest (
DataResourceAbstractName,
StartPosition,Count))
Data Service
SQLRowSetDescription
……, etc
SQLRowSetAccess
GetTuplesResponse (
SQLResponse (SQLRowSet,
SQLCommunicationsArea))
WebRowSet
Potential Relevance to Virtual Observatories
• For existing data models:
– Provide a design for standard
interfaces to Relational and XML
databases.
• Extensibility points:
– Different data models and
languages by extending WSDAI in new specifications.
– Different response formats, by
advertising and selecting
supported representations.
– Different delivery mechanisms,
by implementing data
movement interfaces on
response access services.
• Designed to be usable alone
and to combine effectively with
other standards.
• For specialised data models,
WS-DAI provides a starting point
for designs.
• Advantages:
– Many fiddly design decisions
are made for you.
– Examples exist for use as
templates.
– Consistent with other
realisations:
• Conforms to expectations.
• Quicker learning.
• Able to share implementation
experiences and some code.
• Disadvantage:
– Need to follow the WS-DAI view
of the world.