An information system supporting an organisation is based on concepts from the organisation's institutional world. An institutional world consists of a collection of "speech acts" and "institutional facts". For a group of information systems to interoperate, the organizations responsible for these systems must first agree on what the words mean in the interoperation. This agreement is called an ontology. The ontology is generally defined as an explicit "specification" of a "conceptualization". One of the major uses of ontology is to support interoperation of information systems. Many institutions whose systems are to interoperate are not fully autonomous; they do sometimes cooperate with each other, so that their "institutional worlds" will interlock therefore "interlocking ontologies". Modeling interlocking institutional worlds (IWs) requires a dedicated representation system that gives a formal model which is the "specification of institutional facts" as well as the "specification of speech acts". The ontology is the specification of institutional facts. However, we do not have a system that can give a formal model for the speech acts. Therefore, this paper adopts a synthesis approach to propose the UML extension for modeling speech acts in the context of interlocking institutional worlds. DEMO is one of the most popular Language Action Paradigms (LAP)-based methodologies based on speech act theory so is close to the concept of IWs. The UML is a standard modelling language in the world of information system development and currently there is a growing interest in its adoption as a language for conceptual modeling and business process representation. Taking advantage of the fact that UML is an OMG standard and its use is growing quickly, this paper proposes UML-based DEMO profiles purposely for modelling IWs.