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.

まず、現在 subject–predicate–object のクアッドを書き込んでいる TypeScript のフォームフィールド実装を追跡し、フィールドがどのように設定され、テストされているかを調べます。フィールドが逆方向を選択する方法を定義し、メンバーシップと家系図の例で、順方向と逆方向の両方の関係を表示および書き込みできることを確認します。