Lately, the use of ontologies for semantic description in pervasive systems has been researched and applied in numerous projects. The characteristic of this type of representation for data, services, interfaces, etc. allows the interaction between entities in a pervasive environment and then the development of advanced services. However, pervasive systems include a high number of mobile devices that have to access to several ontology-based information repositories with different representations, interfaces, etc. This fact limits the interaction capacity of mobile devices which have not been designed taking this interaction into account. In this paper we define an access extension for ontology-based pervasive systems that can be automatically generated. Based on the general structure of such systems and on the characteristics of the applications specifically developed to interact with them, we have derived several patterns in order to ease the information lookup and to allow a basic interaction with the system. In this way, we define a set of access patterns based in common structures and interactions. These patterns work in a similar way that design patterns do in software engineering. They are designed independently of the specific ontology implementation and representation. Finally, we present a tool that automatically generates a specific implementation of the defined patterns and we describe a prototype that uses this extension by means of Web Services.