This function is introduced solely for the purposes of translating it via SKSI into the SQL function 'srid' which is defined in the the Open GIS Simple Features Specification for SQL. Given a valid instance of open GIS geometry, the evaluation of this function by a compliant dbms should return the indentification number for the spatial reference system (coordinate system) in which the geometry's coordinate values are represented. See also the corresponding CSQL function, CSQLSRID For Geometry Fn.