assemblerProgram: // standard way of defining model
	content += CommandLine+
    ;

    CommandLine: 
	ControlInstructions | Pointaddress ;

    Pointaddress:
	name = POINTINGADD

    terminal POINTINGADD:('_')('a'..'z'|'A'..'Z')? ('a'..'z'|'A'..'Z'|'_'|'0'..'9')*;

public class MyDslSyntaxErrorMessageProvider extends SyntaxErrorMessageProvider {

	public static final String YOUR_ERROR_CODE = "YOUR_ERROR_CODE";
	
	@Override
	public SyntaxErrorMessage getSyntaxErrorMessage(IParserErrorContext context) {
		if (/* find out */) {
			return new SyntaxErrorMessage(context.getDefaultMessage(), YOUR_ERROR_CODE);
		}
		SyntaxErrorMessage syntaxErrorMessage = super.getSyntaxErrorMessage(context);
	
		return syntaxErrorMessage;
	}
	
}

import org.eclipse.xtext.ui.editor.syntaxcoloring.DefaultAntlrTokenToAttributeIdMapper;

public class AntlrTokenToAttributeIdMapper extends DefaultAntlrTokenToAttributeIdMapper {
@Override
protected String calculateId(String tokenName, int tokenType) {
if(tokenName.equals("RULE_POINTINGADD")){
return SmcHighlightingConfiguration.POINTINGADDRESS_ID;
}
return super.calculateId(tokenName, tokenType);
}
}