2.7 Range Retrieval

Retrieving the contents of a multivalued attribute from a group such as a distribution list can often result in a large number of returned values. A directory service can place limits on the maximum number of attribute values that can be retrieved in a single query.<10> If an attribute has more values than can be returned by the server in a single call, the only way to enumerate all of the attribute values is through the use of the range option.

Range retrieval involves requesting a limited number of attribute values in a single query. The number of values requested must be less than or equal to the maximum number of values supported by the server. To reduce the number of times the query must contact the server, the number of values requested should be as close to this maximum as possible.

To support range retrieval, the WS-Transfer and WS-Enumeration Web Service protocols in the ADWS protocol set require defining an XML representation to return portions of a multivalued attribute or to specify which portion of the attribute to retrieve. The following sections provide an extension to the XML serialization of the data model defined in section 2.3.2 that specifies an XML representation of an attribute with only a portion of its values. They also define extensions to the WS-Transfer [WXFR] and WS-Enumeration [WSENUM] protocols that indicate how a requester is to specify the portion of the attribute values to be returned.