Resource managers (e.g., MapResourceManager) maintain a collection of resource items. These resource items (e.g., MapResourceItem) contain information and references that Web ADF controls use for doing GIS work. The resource item's connection to the server is defined using the GISResourceItemDefinition. This property defines the type of data source (DataSourceType - usually the service type), the data source definition (DataSourceDefinition - typically defines the server and service), Identity used for restricted resources, etc.

In an ASPX page, the GISResourceItemDefinition is stored as a string within the resource item (e.g., MapResourceItem) , which is contained within a resource manager (e.g., MapResourceManager). This string is a serialized XML version of the GISResourceItemDefinition, which may be generated by the FromString method of this class. This string must be HTML-encoded to avoid issues with the containing tags. For example, the "<" character must be encoded as &lt;.

System.Object
   ESRI.ArcGIS.ADF.Web.UI.WebControls.GISResourceItemDefinition

Reference