{
StreamTypeService streamTypeService = new StreamTypeServiceImpl(statementContext.getEngineURI(), false);
ExprTimePeriodEvalDeltaConst timeDelta;
if (expression instanceof ExprTimePeriod) {
ExprTimePeriod validated = (ExprTimePeriod) ViewFactorySupport.validateExpr(viewName, statementContext, expression, streamTypeService, expressionNumber);
timeDelta = validated.constEvaluator(new ExprEvaluatorContextStatement(statementContext));
}
else {
Object result = ViewFactorySupport.validateAndEvaluateExpr(viewName, statementContext, expression, streamTypeService, expressionNumber);
if (!(result instanceof Number)) {
throw new ViewParameterException(expectedMessage);