Redefining keywords in context should throw an exception

[dlongley]

According to #102, we decided that an attempt to redefine a keyword in the context should throw an exception. The spec text in the Context Processing Algorithm (http://json-ld.org/spec/latest/json-ld-api/#context-processing), in step 2.4.3.2, merely ignores these redefinitions.

If we should be triggering an error for this, then this expansion test also needs to be changed/removed (or made into an error unit test ... of which we don't have any yet):

https://github.com/json-ld/json-ld.org/blob/master/test-suite/tests/expand-0043-in.jsonld

[lanthaler]

You are right. I forgot that decision. So, should we throw an error or just ignore it? I don’t have a strong opinion but I think throwing an error might makes slightly more sense in this case. Thoughts?

[dlongley]

I think we should throw an error here; as I do with most context processing issues. I think it's safer to ignore errors like this when processing documents; I'd prefer to be more strict when dealing with contexts since they are reused across many documents and should be refined/fixed.

[lanthaler]

+1

[gkellogg]

+1