Extending OCL to Specify and Validate Integrity Constraints in UML-GeoFrame Conceptual Data Model Topics: Geographical Information Systems; Modeling Formalisms, Languages, and Notations (e.g. UML, ER variants); Models and Frameworks; Requirements Analysis And Management In Proceedings of the 15th International Conference on Enterprise Information Systems - Volume 2: ICEIS, 286-293, 2013 , Angers, France