Microsoft .NET Enterprise Servers and Migration

Microsoft .NET Enterprise Servers represent the next generation of server products for the Windows platform. The .NET Enterprise Servers work hand-in-hand with the Microsoft .NET Framework to bring XML-enabled solutions to market.

This section covers key features supplied by .NET Enterprise Servers that apply to other topics in this guide related to migrations from UNIX, including:

• How .NET Enterprise Servers enable Enterprise Application Integration (EAI) based on XML and Web Services.

• Standardization of XML data interchange by using XML schemas.

• Using XML for data services with enterprise applications.

EAI in a Web Services Environment

An application migration from UNIX to Windows needs to maintain application integration and coordination. Chapter 5, Planning the Migration, of this book considers Enterprise Application Integration (EAI), which links disparate enterprise systems into a cohesive system for performing macro enterprise functions ” at least, that has been the goal for EAI. Certain issues, such as the following, make this goal a challenge:

• Integration standards

• Data exchange

• Application coordination

XML and XML-based services (such as SOAP) address the first two items on the list, but help is still needed for application coordination. Microsoft helps solve this problem with Microsoft BizTalk Server. BizTalk uses XML as its common language for data exchange and it adds coordination between applications.

BizTalk has three major functions:

• Integration definition includes data definitions and mappings. BizTalk Server uses XML schemas for data definitions and XML style sheets (XSL) for data mappings.

• Application messaging performs classic EAI functions including the following:

  • Component integration using COM

  • Web integration using HTTP

  • Queuing support

• Application orchestration enables logical relationships and dependencies to be created between independent applications.

Each of these elements works with the others in an integrated fashion. BizTalk Server orchestration provides the ability to receive or send output to and from the BizTalk messaging engine, process the data from the data definition and mapping functions, and create logical units of work across multiple applications. The logical units of work can include transaction semantics and support.

Web Services can play a role in BizTalk Server systems if you use Web integration features or component integration. This provides system orchestration for applications that expose Web Services.

XML DTD and Schemas

As discussed previously, the self-describing nature of XML introduces a new meaning to interoperability. However, just because an XML document self-describes does not make it usable. Applications still need to know what to look for.

This is where the value of XML schemas and document type definition (DTD) comes into play. By using a published schema, applications can set rules for the content of XML documents. A DTD also describes the content of an XML document. DTDs predate schemas as an XML description mechanism.

The RosettaNet XML implementation represents a good example of XML in action. RosettaNet has developed a standard for data exchange and workflow for business transaction in the electronics industry.

By using a standard such as RosettaNet, partners in a supply chain can agree on the complex semantics of how to fulfill e-business transactions. Using the standard, applications can use BizTalk Server to orchestrate the workflow needed to comply with the RosettaNet specifications. XML is a key technology that allows this to happen.

Although XML schemas and DTDs do not usually affect a migration from UNIX directly, the information can help an organization focus on what tools and technologies are needed after the migration to Windows.

XML-Based Data Services

Not only applications can be migrated from one platform to another. Data forms and structures can also be migrated . For example, developers can migrate legacy data structures to XML.

On the Windows platform, data typically takes two basic forms. The first is structured data, such as a relational database. The second is semistructured data. Microsoft Office documents, such as Microsoft Word or Excel files, represent semistructured data. XML has a place in data services for both structured and semistructured data. Unstructured data can be represented as objects or byte stream data elements in either semistructured data documents or structured databases.

Consider how XML interacts with a relational database. First, a relational database can store XML documents. However, XML can also be used for database queries. With Microsoft SQL Server 2000, Microsoft provides the ability to submit queries by using XML and to retrieve query results in an XML format. In this way, developers can encode the results of an SQL query directly in XML for use in a Web-based application. There is no need to translate the query results into an XML document.

Now, consider semistructured data. Because XML originated as an extensible data definition from a document encoding specification, Structured Graphics Markup Language (SGML), XML is well suited for use with semistructured data. Therefore, the next generation of data storage for semistructured data on the Windows platform is XML-based. This enables document-based enterprise servers, such as Microsoft Exchange and Microsoft SharePoint Portal Server, to use a common XML-based data store. An XML-based data store opens the possibility of using standards-based technologies such as WebDAV (Word Wide Web Distributed Authoring and Versioning) to access the data store.

Now consider developing a data query for a Web Services environment. Because Web Services operate efficiently in an environment where minimal state is maintained between the client and server, it is desirable to have disconnected results for database queries. The concept of disconnected query results is not new, but the .NET Framework version of Active Data Objects (ADO), ADO.NET, creates an XML document to package the results of a query. This provides a convenient way to browse the query results by using XML-enabled development tools.