New version of the VTL 2.0 Extended Backus Naur Form (July 2020)

In the course of these first two years since the publication of the VTL 2.0 specifications, the community of users have progressively submitted suggestions about possible improvements of the VTL grammar (Extended Backus Naur Form – EBNF) and signalled small bugs that prevented them to exploit completely the powerfulness of the language.

The VTL-TF and the SDMX-TWG have now produced a new version of VTL 2.0 EBNF that acknowledges these suggestions and fixes the bugs emerged to date.

The testing activities performed on this new version, also in collaboration with some of the users, have highlighted backward compatibility of its behaviour in respect to the previous version, besides the solution of the reported issues.

Due to the bug-fixing, the new version is also more compliant to the specifications of the VTL User and Reference manuals, which remain unchanged.

The major improvements include:

  • a reorganization of the grammar to avoid potential misinterpretations of the VTL statements by the parser and to obtain better performances in the production and navigation of the graph of operations needed to produce the results;
  • an improved management of the VTL operators, on the basis of their common characteristics, to facilitate the comprehension and the maintenance of the EBNF;
  • a clearer distinction between the operations on VTL Components and on VTL Data Sets in order to simplify the parsing of the rules.