Introduction

This document is the Reference Manual of the Validation and Transformation Language (also known as ‘VTL’) version 2.1.

The VTL 2.1 library of the Operators is described hereinafter.

VTL 2.1 consists of two parts: the VTL Definition Language (VTL-DL) and the VTL Manipulation Language (VTL-ML).

This manual describes the operators of VTL 2.1 in detail (both VTL-DL and VTL-ML) and is organized as follows.

First, in the following Chapter “Overview of the language and conventions”, the general principles of VTL are summarized, the main conventions used in this manual are presented and the operators of the VTL-DL and VTL-ML are listed. For the operators of the VTL-ML, a table that summarizes the “Evaluation Order” (i.e., the precedence rules for the evaluation of the VTL-ML operators) is also given.

The following two Chapters illustrate the operators of VTL-DL, specifically for:

  • the definition of rulesets and their rules, which can be invoked with appropriate VTL-ML operators (e.g. to check the compatibility of Data Point values …);

  • the definition of custom operators/functions of the VTL-ML, meant to enrich the capabilities of the VTL-ML standard library of operators.

The illustration of VTL-ML begins with the explanation of the common behaviour of some classes of relevant VTL-ML operators, towards a good understanding of general language characteristics, which we factor out and do not repeat for each operator, for the sake of compactness.

The remainder of the document illustrates each single operator of the VTL-ML and is structured in chapters, one for each category of Operators (e.g., general purpose, string, numeric …). For each Operator, there is a specific section illustrating the syntax, the semantics and giving some examples.