Allow any form field to be represented by reverse arc in the graph

All the form fields at the moment assume that they are given a subject X and a predicate P and the form will write a quad (X, P Y, G).

In fact, when not dealing with literals for Y, RDF is symmetrical: it is just as reasonable for them to correspond to the data (Y, P, X, G). So we need to be able to specify in a form, that a given field is in the inverse direction.

Examples:

• When a user is a member of a group, the triple (user, member, group) could turn up in a form about the user - or a form about the group.

• In a family tree user interface form, the same form could allow adding a number of (this, child, Y) triples to list one's children, and also a set of (Y, child, this) triples for giving ones parents.

Commencez par suivre l’implémentation TypeScript du champ de formulaire qui écrit actuellement des quads sujet–prédicat–objet, et examinez comment les champs sont configurés et testés. Définissez comment un champ sélectionne la direction inverse, puis vérifiez que les relations dans les deux directions, directe et inverse, peuvent être affichées et écrites pour les exemples d’adhésion et d’arbre généalogique.