Despite a lot of attention gained by the Resource-Event-Agent (REA) framework among researchers in enterprise modeling, it still lacks comprehensive formal description. Most of the formalization approaches to REA use only UML or other graphical representation. This paper aims to define REA ontology at operational level using formal logic tools. The general approach to formal logic description of REA was motivated by LTAP introduced by Ito, Hagihara and Yonezaki. After basic REA concepts are presented, semantics and logical language LREA are defined including axioms for the REA operational level. Future research is shortly described in conclusion
