Running PRISM /

Support For PEPA Models

For CTMCs, PRISM also accepts model descriptions in the stochastic process algebra PEPA [Hil96]. The tool compiles such descriptions into the PRISM language and then constructs the model as normal. The language accepted by the PEPA to PRISM compiler is actually a subset of PEPA. The restrictions applied to the language are firstly that component identifiers can only be bound to sequential components (formed using prefix and choice and references to other sequential components only). Secondly, each local state of a sequential component must be named. For example, we would rewrite:

  • P = (a,r).(b,s).P;


  • P = (a,r).P';
  • P' = (b,s).P;

Finally, active/active synchronisations are not allowed since the PRISM definition of these differs from the PEPA definition. Every PEPA synchronisation must have exactly one active component. Some examples of PEPA model descriptions which can be imported into PRISM can be found in the prism-examples/pepa directory.

From the command-line version of PRISM, add the -importpepa switch and the model will be treated as a PEPA description. From the GUI, select "Model | Open model" and then choose "PEPA models" on the "Files of type" drop-down menu. Alternatively, select "Model | New | PEPA model" and either type a description from scratch or paste in an existing one from elsewhere. Once the PEPA model has been successfully parsed by PRISM, you can view the corresponding PRISM code (as generated by the PEPA-to-PRISM compiler) by selecting menu option "Model | View | Parsed PRISM model".

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