INTRODUCTION implementation. After Booch, Jacobson, and Rumbaugh popularized

INTRODUCTION implementation. After Booch, Jacobson, and Rumbaugh popularized decomposition of any computing problem with a set of well-known modeling techniques, the saying in the computing world became Programmers just like to program with objects. It makes their job easier because it makes the problem domain easier to visualize. Techniques such as top- down design and structured programming have taken a backseat ever since. But data in a relational database such as SQL Server is decomposed into tuples and relations, not into object graphs. Therein lies the famous object-relational impedance mismatch. ObjectSpaces is a client-side object-relational integration technology that will be delivered as part of ADO.NET. This technology solves the problem of every programmer writing different code to coerce multiple rectangular Rowsets into object graphs that make up their programming object model. Since most client applications are built around object models, a standard set of APIs to ease the interaction between relational data and objects will be a welcome addition. In the past few years, the concept of entity objects was popularized, but this concept has suffered, in general, from poor performance. In addition, entity objects usually were implemented in such as way as to produce far too many database round-trips and/or database locks held for too long to be useful. ObjectSpaces employs optimization techniques such as partial and lazy loading of object graphs, including programmer specification of graph loading depth and smart updates and deletions of database rows corresponding to graph instances, to increase performance. ObjectSpaces graph accessor queries and mutators can be specified as stored procedures, to take advantage of SQL Server s processing power. In addition, you can query object graphs on the client side through an ObjectQueryclass and a simple but powerful predicate language known as OPath. Using OPath is reminiscent of using XPath to select a subset of nodes in an XML document or using a WHEREclause in a SQL query. Chapter 14 rounds out the discussion of relational data, object data, and XML with a discussion of Microsoft s object solution for the client or middle tier and its integration with SQL Server. Extending SQL Server into the Platform Service Broker and Notification Services Finally, SQL Server 2005 adds two more pieces of data access and application programming functionality that bear mention. SQL Server Service Broker allows you to use T-SQL to send asynchronous messages. These

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