A static data type consists of data together with operations onthem. Such data types are classically modeled by multisorted algebrasand specified using a logic or, in other words, using a particularinstitution. A dynamic data type is a static data type together with anassignment mechanism; the name stems from the fact that the assignmentmechanism provides the static data type with a dynamic behavior. Byviewing states as data according to the classical state-as-algebraapproach, it is possible to specify dynamic data types along the samelines as static data types, namely, by institutions.

Essentially, the paper associates with an arbitrary institution SFan institution DF(SF) satisfying the following property: if a staticdata type is specified using SF, then a dynamic data type built uponthis static data type may be specified usingDF(SF). The paper is a continuation of work done bythe author and Egidio Astesiano.

The paper is clearly structured. It begins with anextended and illuminating example illustrating the fundamental ideas andproblems. In spite of their simplicity, these ideas lead to a heavyformalism. Understanding this work requires some acquaintance withcategory theory or, at least, with institutions. On the other hand, thenumerous comments allow readers to grasp the main ideas behind thenotions introduced. The paper restricts itself to abstract theoreticalresults and does not provide hints about practical applications. A fewmisprints (for example, the satisfaction condition in Definition 4) anda poor English style make it harder to read. In spite of itsdeficiencies, however, the paper presents clearer and more substantialresults and is easier to understand than most other papers on thesubject.