Databases are the place where many different client data access technologies need to intersect, making the repositories natural candidates for Web services.
Database vendors have seen this convergence coming, and a number of them have already released first-generation Web services features for their databases.
Microsoft Corp.s SQL Server 2000 has the simplest and easiest-to-deploy Web services features eWeek Labs has seen, through its free and fully supported SQLXML 3.0 add-on for SQL Server 2000 (downloadable from www.microsoft.com/sql). SQLXML also requires that a number of other Microsoft technologies be installed, particularly Microsofts SOAP (Simple Object Access Protocol) Toolkit 2.0 SP2 and its IIS (Internet Information Services) Web server (which is used to publish SOAP services).
SQLXML allows data to be returned to clients making Web service calls to a SQLXML-enabled IIS Web server. Simple queries (or, more commonly, Transact-SQL stored procedures) can be published as SOAP services, and customers can also choose to transform output XML data before sending it back to the caller. A tool to bulk-load XML data into SQL Server is also included. The tool kit works with Visual Studio 6 and Visual Studio .Net development tools.
Oracle Corp., IBM and Sybase Inc. all rely on their application servers to provide Web service interfaces to database data. All three companies now provide built-in tools to return database data in XML format, including transformation support to reformat XML into a desired schema.
To turn this raw XML data into a Web service, database administrators need to wrap this output into a Web service and publish it through the normal Web service support provided in all three companies application servers. This approach isnt as simple as Microsofts self-contained Web service features, but all the pieces are there.
IBMs DB2 8.1, which ships this fall, will also include the ability to make an external Web service look like a SQL table to SQL clients, providing a seamless interface to real-time data sources. (This functionality will require WebSphere.)
The XML database space is also moving toward Web services as an access technology, as might be expected since these products store data directly in XML format anyway.
Ipedo Inc.s Ipedo XML Database 3.0 currently supports database queries sent in SOAP format, in addition to its Java and Component Object Model query interfaces.
NeoCore Inc.s XML database NeoCore XMS 2.6, which started shipping last month, provides a REST (Representational State Transfer)-style Web service interface to its data. REST, a URL-based access mechanism, isnt as popular a Web service technique as SOAP. NeoCore plans to add a SOAP interface in its 2.7 release due next quarter.