Site Group Identifier

A site group identifier is a 4-byte integer value used to uniquely identify a site group within a site collection. Site group identifiers are assigned from the same numbering space as User Identifiers and cannot overlap. Values of -1 and 0 are reserved to indicate invalid or unknown site group identifiers.

For example, by default, Windows SharePoint Services 3.0 creates three implementation-specific site groups with default site group identifiers for use in role assignments when provisioning a new site collection: "Site Owners" (3), "Site Visitors" (4), and "Site Members" (5).