| Platform SDK: Exchange 2000 Server |
[This is preliminary documentation and subject to change.]
Content classes are data classes that describe sets of Web Store item properties. A content class defines types of content in terms of the expected properties stored along with the item. It does not explicitly define a property stored with an item but rather provides the means for applications to ascertain the purpose of particular Web Store items and what properties are available.
A good example of a content class is an expense report. An expense report could be in the format of a Microsoft® Excel document, a Microsoft® Word document, or an e-mail message. However, regardless of the format, there may be a common set of properties that describe an expense report. For example, the date range of the report, the total dollar amount of the report, and the approval state of the report. A content class could be set on all expense reports to indicate that they all use a common set of shared properties. Another benefit is that a content class value on an item can make parsing content unnecessary by an application that attempts to determine the nature of the data.
Content classes support single and multiple inheritance from other content classes. The Web Store provides the urn:content-class:item content class for properties that enable you to manipulate Web Store items and check their status. These default properties are in the schema folder located in the non-IPM subtree of the default store.
A content class is used frequently by applications to do the following:
Do not confuse content class with content type. Content classes are not necessarily tied to the content type (data format) of an item.
The following figure shows the relationship between property and content class definitions and how you can inherit from a content class by extending it in the content class definition.