## Event-based automaton projection

The event-based automaton projection takes an automaton and a subset of the events of its alphabet that should be preserved. The other events of the alphabet are considered to be internal steps and get replaced by `epsilon` at the edges. The algorithm produces a deterministic automaton with the subset as its alphabet that has the same language.

The tool takes a `.cif` file containing one automaton, and the names of the events that should be preserved. In addition, the general event-based restrictions apply as well.

The output is a `.cif` file containing a deterministic automaton that is language equivalent with the input automaton with respect to the set of preserved events. The resulting automaton has the same kind as the input automaton. The resulting automaton is a DFA that it is not necessarily minimal, but can be minimized using the DFA minimizer.

### Starting the automaton projection tool

The tool can be started in the following ways:

- In Eclipse, right click a `.cif` file in the Project Explorer tab or Package Explorer tab and choose CIF synthesis tools Event-based synthesis tools Apply automaton projection…​.

- In Eclipse, right click an open text editor for a `.cif` file and choose CIF synthesis tools Event-based synthesis tools Apply automaton projection…​.

- Use the `cifproj` tool in a ToolDef script. See the scripting documentation and tools overview page for details.

- Use the `cifproj` command line tool.

### Options

Besides the general application options, this application has the following options:

- Input file: The absolute or relative local file system path to the input CIF specification.

- Preserved events: Comma and/or whitespace separated absolute names of events that should be preserved.

- Output file: The absolute or relative local file system path to the output CIF specification. If not specified, defaults to the input file path, where the `.cif` file extension is removed (if present), and a `_projected.cif` file extension is added. The `projected` part of the default extension depends on the Result name option.

- Result name: The name to use for the projected automaton. If not specified, defaults to `projected`. Also affects the Output file option.

- Add state annotations: Add state annotations to the locations of the automaton in the output CIF file. This option is enabled by default. If the output CIF file has an automaton with only a single non-initial location, then the location does not get a state annotation, regardless of whether the option is enabled or not.