the change to replace "must" with "should" for ill-typed term values should be reverted pending further discussion

[lisp]

a recent pull request which was performed to the concepts document which had the side effect of replacing the requirement, that ill-typed terms must be supported with the suggestion that they should be supported.

this change was premature. in the most recent discussion of the topic, it was agreed that the concerns and consequences were sufficiently complex, that a group chair would draft a summary document as the basis for further discussion.
that is yet to happen.