XMLhas become a vital interoperability tool and a core component of many applications. Visual Studio .NET uses XML as its main programming infrastructure for intra-object communications and to create project files. Here are the seven XML document types that developers use most often in SQL Server database applications.

7. Standard XML Documents


XML documents are ASCII text documents formatted according to the World Wide Web Consortium's (W3C's) XML rules. XML is flexible, and you can use XML documents to do everything from creating Web pages to transferring data to a database.

6. XML Templates


An XML template is an XML document that contains database queries or commands. You usually store template files in Microsoft IIS virtual directories and use them to send SQL and XPath queries to a database server. Templates are more flexible and secure than URL strings for specifying queries.

5. Updategrams


Updategrams are XML documents containing tags that let the XML document insert, update, and delete rows in a SQL Server table. One updategram can send several database actions to a server. You send updategrams to SQL Server by using HTTP and use them much like you do templates.

4. DiffGrams


DiffGrams are a subset of the updategram document that SQL Server 2000 supports. Whereas you typically use updategrams to update SQL Server databases with XML information, you use DiffGrams to update ADO.NET DataSets. ADO.NET uses DiffGrams to capture DataSet changes.

3. XDR Documents


XML Data Reduced Schema (XDR) is a special-purpose XML standard that Microsoft developed to provide an XML view of relational databases. XDR documents map rows from a database table or view to XML and map column values to attributes or elements. The more modern XML Schema Definition (XSD) standard has replaced the XDR standard, but you can still find XDR documents because many pre-XSD applications use this model.

2. XSD Documents


The XSD language lets you define the XML document structure and data types. XSD documents are similar to SQL Data Definition Language (DDL) documents, but you apply them to an XML document instead of to a database. An XSD file can define an entire order document and the data elements that make up that order. XSD documents can also define complex elements, data relationships, and element mapping to relational database entities.

1. XSL Documents


Extensible Style Sheet (XSL) documents are special-purpose XML documents that describe how to format XML data. For example, you can use an XSL document to describe how to convert the contents of an XML document into HTML.