Schema {
    public static CDDef readDefinition(ClassGraph cg,
				       String fileName) throws Exception
    {{
	return readDefinition(cg, fileName, null);
    }}

    public static CDDef readDefinition(ClassGraph cg,
				       String fileName,
				       CDDef def) throws Exception
    {{
	Schema schema;

	// Open the specified schema-definition file and parse its contents to
	// create the schema object.  But before parsing it, pre-process it to
	// remove comments, etc. and make changes necessary for the parser.
	try {
	    BufferedReader reader =
		new BufferedReader(new FileReader(fileName));
	    schema = parse(Preprocessor.preProcessSchemaDefinition(reader));
	}
	catch (FileNotFoundException e) {
	    throw new Exception("Schema definition file '" + fileName + "'" +
				" not accessible.");
	}
	catch (IOException e) {
	    throw new Exception("Error in reading schema definition file '" +
				fileName + "'");
	}
/*
schema.print();
System.out.println();
*/


	// Create an empty CDDef object if none already exists
	if (def == null)
	    def = CDDef.parse(" ( ) ( )");

	// Traverse the schema object to extract the element, attribute and
	// type definitions
	TraversalGraph tg =
	    new TraversalGraph("from Schema bypassing -> *,tail,* to *", cg);
	SchemaVisitor sv = new SchemaVisitor(def);
	tg.traverse(schema, sv);
	String namespacePrefixes[] = sv.getNamespacePrefix();
/*
def.print();
System.out.println();
System.out.println("Namespace prefix = '" + namespacePrefixes[0] + "'.");
*/

	return def;
    }}


    public void print() bypassing -> *,tail,* to * (DisplayVisitor);
}