In this paper we present OASIS 2.1, the last version of OASIS. OASIS is a formal, OO Specification Language developed in DSIC ([1] [4] [6] [8] [7] [12] [11]). In its initial versions, the Software Development Environment associated to the Language was formalized using first order theories that evolve over time. This lead us to a Logic Programming environment with the complement of a for dealing with dynamics. But as will be shown later, it has a natural, sound and complete formal basis within the context of Dynamic Logic. A new formalization of OASIS according to this view is presented in this paper, in order to properly characterize objects as observable processes. The language expressiveness has been thus enriched, trying to balance ease for specification use and a precise formal framework. Additionally, language implementations have been built for rapid prototyping purposes by generating logic prototypes (implemented in logic programming languages) functionally equivalent to any given OASIS specification.