Policies in Content Types
If you assign a site policy to a given content type, you cannot make changes to the policy at the content type level. For example, you cannot assign a site policy to a content type and then customize the policy in that content type to include additional policy features.
However, you can export the site policy as an XML file, and then import the XML file into a content type. This does not establish a relationship between the site policy and content type policy. You can make changes to the content type policy, but any changes you make to the site policy cannot be pushed down to the content type policy.
You can derive a policy from another policy in two ways:
You can assign a site policy from the policy collection to a specific content type or list.
You can create one content type based on another content type.
When you create a content type that is based on an existing content type, all aspects of the derived content type are copied from the existing content type, including the policy applied to the initial content type. A new policy instance is copied locally into the derived content type.
If you make changes to the policy instance in the initial, "parent" content type, Office SharePoint Server 2007 updates the derived policies to include these changes. However, you cannot make changes directly to the policy in the child content type.
Storing Policy Information in Content Types
The actual XML file representing the policy instance is stored within a content type definition in the XMLDocuments collection. When a content type is assigned to a specific 2007 Microsoft Office system document, certain content type information is demoted and stored in the document itself. This includes the policy for that content type. Copying the policy into a document ensures that the policy remains tightly bound to the document. Policy information in the document is read-only to the 2007 Microsoft Office system document.
For more information about the XMLDocuments element and the content type definition in general, see Content Type Definition Schema in the Microsoft Windows SharePoint Services 3.0 SDK.
When you assign a content type that contains an information policy to an item, policy features in that policy may also store metadata on the item itself. For example, the Bar Code policy feature adds a Bar Code column to each item to which it is applied.