State-Machines and Code Generation

Generating Code from State-Machine Diagrams

We introduce the ability to generate code from state-machine diagrams in version 0.2.3 of the code generation feature plug-in. Code is generated from the diagram itself, and no additional mark-up of the model is required; that is, nothing over and above the usual mark-up required for Tasking Event-B, such as identifying non-typing/typing invariants, and guards etc. State-machine(s) are created in a machine using the existing state-machine plug-in, subject to the limitations described below.

Limitations/What Can Be Translated

The current code generation tool is restricted to generating code for a single Event-B machine containing one or more state-machines. We have yet to explore the decomposition/composition of machines containing state-machines. In principal we should be able to apply decomposition techniques to decompose the single Event-B machine with state-machines into a number of machines, with the state-machines distributed between them.

Another limitation is that we do not handle nested state-machines, although this should be feasible.

Translations

< Diagram here >

The translation of the diagrammatic elements to code has been hard-coded in the code generation plug-in. We have introduced new types to the translator's common language model (IL1). We add case-statements and a container for them, since these are commonly used to implement state-machines.

Each state-machine has an Enumerated type whose elements are the names of the states. A variable is introduced to the

Initial state

Single outgoing transition

Multiple Outgoing transitions