Complex Event processing (CEP) usually focuses on analyzing raw atomic events in order to detect composite events. Usually, a composite event is defined as the pattern actively searched by a CEP system. However, considering uncertainty in some paradigms, such as internet of things, is still an open issue. In current approaches the confidence value related to the occurrence of an event is usually not communicated to the CEP system. As a consequence, a complex event pattern doesn’t take this information into account. Nevertheless, even if static, they are useful for pattern definition and particularly for a more accurate constraint definition. We propose to manage this information through domain ontologies. In this paper we describe the architecture for the enrichment of CEP queries to enable evolutivity and flexibility in CEP systems according to event sources [9].