The European E-Invoicing Service Providers Association (EESPA), of which Order2Cash is a member, and OpenPEPPOL have published a joint paper on the subject of the European Norm (EN) for the semantic data model for a core electronic invoice. In particular, the paper suggests imposing a restriction in the number of syntaxes to be used when formalising the standard.
EESPA and OpenPEPPOL are very concerned by the provision in the Directive 2014/55/EU (the Directive) that all public sector contracting authorities (over 300,000 in Europe have been mentioned) will need to be able to receive electronic invoices expressed in any of a list of up to four syntaxes (technical languages) to be recommended by CEN TC 434 during the preparation of the standard for a European core invoice. Both associations strongly recommended that members of CEN TC 434, national standards organisations, the European Commission and other stakeholders take note of the points made in this paper, which is written with the success of the standard in mind and from a hands-on practical perspective.
You can read the full paper online at the EESPA website: http://eespa.eu/position-paper-requirement-to-receive-electronic-invoices-in-the-listed-syntaxes-under-directive-201455eu/