ITU-T Recommendations

Recommendation ITU-T Z.106 defines the common interchange format of Specification and Description Language (SDL-CIF). The SDL-CIF is intended for the interchange of graphical SDL-2010 specifications (SDL-GR) made on different tools that do not use the same storage format. Prior to the definition of SDL-CIF, the textual phrase representation of SDL-2010 (SDL-PR) was used to interchange specifications with the disadvantage that all graphical information was lost, making the same specifications often look very dissimilar in different environments. With the SDL-CIF, this disadvantage is reduced to a minimum, as it contains most of the graphical information. The SDL-CIF improves the independence from specific tool vendors and allows standards bodies to accept specifications in SDL-CIF irrespective of the tool they use for their internal work. This also improves productivity by allowing specifications to be made on the accustomed tool. All SDL-2010 tool vendors are encouraged to provide facilities for importing and exporting SDL-CIF.

This Recommendation defines how SDL-2010 descriptions are stored in order to be interchanged between tools coming from different vendors. It does not take into account the message sequence chart (MSC) notation. SDL-CIF is an optional part of SDL-2010. SDL-CIF is based on the SDL-PR syntax, the textual phrase representation of SDL-2010 also defined in this Recommendation. SDL-CIF is readable and written by tools as well as users. All the constructs available in SDL-2010 are able to be expressed in graphical form or in the purely textual SDL-PR form. Constraints on graphical presentation are expressed in SDL-CIF by adding specific annotations to SDL-PR. As a result, most SDL-PR descriptions are legal SDL-CIF descriptions. SDL-CIF is an open storage format as it includes a mechanism of tool-specific directives. This mechanism allows an SDL-CIF-compliant tool to extend the format by adding specific information. SDL-CIF is also easily implemented and provides tool vendors with two levels of tool conformance and concepts of mandatory and optional directives.

SDL-PR is an alternative text-only syntax for the Specification and Description Language. Before 2002, SDL-PR was published as part of ITU-T Z.100, but as the main use of this notation is for communication within and between tools the definition has been moved to this Recommendation. SDL-PR is Level 0 SDL-CIF and allows the interchange of syntactically complete SDL-2010 descriptions, usually as a single file per system. Conformance to SDL-PR requires the model to conform to the corresponding semantics defined in Recommendations ITU-T Z.101, ITU-T Z.102, ITU-T Z.103, ITU-T Z.104, ITU-T Z.105 and ITU-T Z.107.

This Recommendation introduces two further levels of SDL-CIF. Two further conformance levels are defined, one at a more liberal SDL-PR level and the second including graphical information. The complete grammar is described with the related semantics. Mandatory and optional directives are described, as well as the format for tool-specific directives. Current tool-specific directives are described in Appendix I.

Two levels of SDL-CIF conformance are defined as level 1 and level 2. Level 1 is very close to SDL-PR, but it supports incomplete descriptions in SDL-2010. Level 2 includes level 1 and is able to capture most of the graphical information of SDL-GR diagrams. An SDL-CIF specification shall identify which of these two levels it complies with. Similarly, tool vendors that use the SDL-CIF should also identify the SDL-CIF level they comply with for their import and export functions.