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The components of the SkyQuery web service:
- The Portal: The XML (.NET) Web service providing an entry point into the
Distributed Query network, which relies on the metadata and query
services of the database SkyNodes.
- SkyNodes:
Individual databases located at different sites, along with their XML (.NET)
Web Service wrappers.
- Clients:Each client can be an
applet-based query interface along with a SOAP client. Currently we have an ASP client
available for testing.
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The steps of processing a query:
- Each database indicates its
willingness to participate in the query processing by registering its
catalog information with the portal. Since the SkyNode web services are
internal (not UDDI-registered), this information is made available via
the file.In the future, when the SkyNodes
are also UDDI-registered, this will be done dynamically by sending a
registration SOAP message by the corresponding UDDI server.
- The user submits the query
via the ASP client to the portal. The portal parses the query into sub-queries
which are specific to each database. This is done by using metadata
information available through Metadata Services from the SkyNodes.
- The sub-queries are first
transformed into queries which count the number of rows that the
original sub-query will produce. These are sent as .NET RPCs to the
corresponding SkyNodes.
- The web service at
each database node interprets the message, the database executes the
query and sends the XML reply back to the client packaged as a DataSet.
SkyQuery was supported by grants from NASA (AISRP 2001) and NSF (KDI).
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National Virtual Observatory
