peer reviewedIf we take a look at existing LOTOS specifications, we notice that the description of the needed data types is very often huge. This causes the lack of concision of most descriptions of complex systems. We propose to tackle this problem in two steps. First, we define extensions to the LOTOS language allowing short definitions of most of the data types used in practical LOTOS specifications. Second, we propose a tool called `'DAFY'' (Data Facility Compiler) which is able to translate these extensions into standard LOTOS