Parser.md

DOPLER Decision Parser

The DOPLER parser is ANTLR-based with separate lexer and parser grammars and processes an input file (JSON or CSV) in two consecutive listener passes — first to create the Decision objects, second to parse and attach expressions (constraints / visibility conditions) to those previously created decisions.

This two-pass / multi-listening design is necessary because the input must not enforce a fixed order of decisions and expressions: only after all decisions exist can references like getValue(X) or isTaken(Y) be reliably resolved.

Setup

Reads the input from the file and creates the corresponding lexer, tokens and parser.

		String fileName = "dm_dopler.json";
		CharStream input = CharStreams.fromFileName(fileName);
		DoplerLexer lexer = new DoplerLexer(input);
		CommonTokenStream tokens = new CommonTokenStream(lexer);
		DoplerParser parser = new DoplerParser(tokens);

Create Parse Tree

Creates the corresponding parse tree of the earlier input, by calling the first parser rule. The tree can be traversed with a ParseTreeWalker.

        ParseTree tree = parser.document(); 
        ParseTreeWalker walker = new ParseTreeWalker();

Two-Pass Walk

Performs two consecutive listener walks: the first constructs all decisions, and the second parses expressions and attaches them to their corresponding decisions.

		DoplerDecisionCreator decisionCreator = new DoplerDecisionCreator(fileName);
		walker.walk(decisionCreator, tree);
		DoplerExpressionParser expressionParser = new DoplerExpressionParser(decisionCreator.getDopler());
		walker.walk(expressionParser, tree);

Extract Dopler Model

After walking through both listeners, the resulting Dopler model can be obtained from the DoplerExpressionParser.

		Dopler dopler = expressionParser.getDopler();

Write Dopler Model

The DoplerModelWriter can be used to export the parsed model either as JSON or CSV.

		DoplerModelWriter dmw = new DoplerModelWriter();
		dmw.writeCSV(dopler, Paths.get("output_dm_dopler.csv"));
		dmw.writeJson(dopler, Paths.get("output_dm_dopler.json"));