Semantic integrity constraints specify relations between entity classes. These relations must hold to ensure that the data conforms to the semantics intended by the data model. For spatial data many semantic integrity constraints are based on spatial properties like topological or metric relations. Reasoning on such spatial relations and the corresponding derivation of implicit knowledge allow for many interesting applications. The paper investigates reasoning algorithms which can be used to check the internal consistency of a set of spatial semantic integrity constraints. Since integrity constraints are defined at the class level, the logical properties of spatial relations can not directly be applied. Therefore a set of 17 abstract class relations has been defined, which combined with the instance relations enables the specification of integrity constraints. The investigated logical properties of the class relations enable to discover conflicts and redundancies in sets of spatial semantic integrity constraints.