V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

FDT
       Formal Description Technique


The Free On-line Dictionary of Computing (30 December 2018):

Formal Description Technique
FDT

    (FDT) A formal method for
   developing telecomunications services and protocols.  FDTs
   range from abstract to implementation-oriented descriptions.
   All FDTs offer the means for producing unambiguous
   descriptions of OSI services and protocols in a more
   precise and comprehensive way than natural language
   descriptions.  They provide a foundation for analysis and
   verification of a description.  The target of analysis and
   verification may vary from abstract properties to concrete
   properties.  Natural language descriptions remain an essential
   adjunct to formal description, enabling an unfarmiliar reader
   to gain rapid insight into the structure and function of
   services and protocols.

   Examples of FDTs are LOTOS, Z, SDL, and Estelle.

   [ISO/IEC DTR10167: "Guidelines for the application of
   Estelle, LOTOS and SDL"].

   (1994-12-06)