In the Factory of the Future, wireless communication will play an important role. DECT, the European standard for digital cordless telecommunication is considered to be the prime means for realizing a wireless infrastructure for data communication in industrial environments. In this paper, we consider the following situation: When different owners of mobile communication equipment will be forced to communicate with each, other on the factory floor, the task of interweaving their communication streams becomes difficult, In terms of telecommunications, the "roaming problem" must be solved. Alas, DECT's support for roaming is only on a local basis, meaning a single domain or "island". We propose the OSI X.500 Directory Service as a standard solution for DECT's mobility management. Its Suitability for mobile management application needs not be verified, as this was already done in [1]. Instead, the prototype of an Interworking Unit will be verified by use of simulations, Without roaming, the integration of DECT into the Factory of the Future will be limited to local Private Branch Exchange (PABX) functionality.