A schema defines the universe of objects stored in a directory. In Active Directory®, the schema specifies what attributes a directory service object can, or must, have. It also specifies the value range and the syntax of the attributes and whether they support single or multiple values. In short, the schema is organized by class definitions, attribute definitions, and attribute syntax. ADSI provides three interfaces for reading attribute, class, and syntax data from a schema: IADsClass, IADsProperty, and IADsSyntax.
Active Directory uses a set of schema objects to provide dynamically extensible schema management. For more information about an unknown object, look up its associated schema objects. To create a new class definition or extend an existing class definition, you can create or extend the appropriate schema objects. Schema objects are organized in the schema container of a given directory. To access an object schema class, use the object Schema property, that is the _ property method, to obtain the ADsPath string and use that string to bind to an IADsClass interface on the object schema class.
To determine attribute definitions, that is, the range of values, the syntax, and so on, inspect the schema attribute objects for each property supported by the directory service object. For more information about how to access the schema attribute objects, see IADsProperty.
ADSI abstracts the syntax data as necessary and enables you to use IADsSyntax to identify the syntax required to represent object data.
For more information about the Active Directory schema, see Active Directory Schema.