From The BABEL Development Site
Revision as of 17:42, 21 May 2009 by Jlblanco (talk | contribs) (Basic types)

BABEL Definition Language (BDL)

v. 120606

A data definition language for the BABEL development system.

System Engineering and Automation Department.

University of Málaga, Spain.


What is BDL?

BDL (Babel Definition Language) is the medium for specifying, in a programming-language independent fashion, some data types that a BABEL module needs. BDL has been implemented as a restricted subset of one of the most extended definition languages: the OMG CORBA IDL (

Where the BDL types are used?

It is used currently for defining input/output parameters of services and for providing public definitions (data types that the module provides to other modules and to itself). You can use BDL types both in the "Public Definitions" of the module and in the specification of the input/output parameters of the services. You can compose your own types (using "typedef") based on BDL basic or composed types.

What the BDL types are used for?

You can use a variable of a BDL type in the following situations: A) Creating a local variable for the internal use of some logic of the module (auxiliary logic, service logic, start-up logic, etc.). B) Creating a global variable for the internal status of the module (accessible from any logic of the module). C) Using an already defined input/output parameter of a service.

How variables of the BDL types are used?

You should remember that BDL is not a programming language (only a specification for data), and thus, you cannot use directly any BDL type in your codification logics. Rather, BABEL translates automatically for you the BDL types into types understandable by the codification language you have chosen for your module (see for example the Using BDL in the C++ codification language section).

BABEL Definition Language (BDL)

Basic types

Numeric (octet, short, long, ...)

BDL includes the following basic numeric types:

  • octet : 8-bit, unsigned (0...2^8-1)
  • short : 16-bit, signed (-2^15...2^15-1)
  • unsigned short : 16-bit, unsigned (0...2^16-1)
  • long : 32-bit, signed (-2^31...2^31-1)
  • unsigned long : 32-bit, unsigned (0...2^32-1)
  • long long (*) : 64-bit, signed (-2^63...2^63-1)
  • unsigned long long (*) : 64-bit, unsigned (0...-2^64-1)
  • float : IEEE single-precision floating point numbers.
  • double : IEEE double-precision floating point numbers.

(*): The 64-bit integer types (long long and unsigned long long) could not be available in some implementations, being mapped in an undefined way, so its use should be avoided.

Alphanumeric (char)

BDL has only one basic alphanumeric type:

  • char : One unsigned 8-bits character.

There is also one composed alphanumeric type: string.

Others (boolean)

BDL includes one basic type for logical operations:

  • boolean : Stores a boolean value (TRUE or FALSE)

Composed types

Data type alias (typedef)

Constants (const)