When developing for Windows SharePoint Services 3.0, you are often required to create and modify XML files that contain Collaborative Application Markup Language (CAML). It is recommended that you configure Microsoft Visual Studio on your development workstation to reference a XML schema file named WSS.XSD so that IntelliSense works properly when working with CAML-based files.
Create a new text file and name it CAML.xml. Add the following code.
<Schema href="C:\Program Files\Common Files\Microsoft Shared\
web server extensions\12\TEMPLATE\XML\wss.xsd"
The file path assigned to the href attribute within the schema element in this code snippet should be placed on a single line. A line break has been added here to make the code more readable inside this document.
Where does the CAML.XML file go?
Next, save CAML.XML to C:\Program Files\Microsoft Visual Studio 8\Xml\Schemas\CAML.xml.
Shut down and restart Visual Studio. At this point, IntelliSense should be available whenever you work with CAML-based files that rely on the http://schemas.microsoft.com/sharepoint/ namespace.
Visual Studio has a special directory (C:\Program Files\Microsoft Visual Studio 8\Xml\Schemas\CAML.xml) that it uses to maintain a catalog of XML schemas that drive its IntelliSense feature. The installation of Visual Studio adds to this directory a standard file named catalog.xml that contains XML that references standard XML schemas. These schemas drive the default IntelliSense support that is included as part of Visual Studio. However, this mechanism is completely extensible. You can simply create another file with an .xml extension that references other, non-standard XML schemas and copy the file to the same directory. After copying this file to the correct location, you must restart Visual Studio. That's because Visual Studio examines all the XML files in this directory at startup to determine which XML schemas it should load to drive IntelliSense.