Conclusions from the constraints spec review

After reading through the messages sent on this topic, and after
consulting with the editors, the chairs have reached the following
conclusions and action plans:

- We will keep the Constrainable interface, with the current structure.
- We will make one registry of constraints, common across all usages.
- We will change the type of ConstraintSet to be a typedef of Object.

Details on each of these:

The trigger for breaking out the Constrainable interface was a request
from Jim (editor of MediaStreamRecorder) to have an interface he could
reuse, rather than having to respecify constraints from scratch if he
wanted to reuse the pattern.
We believe the breaking out makes the interface reusable, as requested,
and also makes the specification clearer and easier to read. Both are wins.
We'll allow the discussion of whether constraints make sense for
MediaStreamRecorder to continue (I have some opinions on that), but
believe that the separate interface has value anyway.

As Jan-Ivar pointed out, having one constraint name mean different
things in different contexts can be confusing. It can also cause
practical problems for some toolchains. But strings are cheap; there
seems little cost to requiring that interfaces that want a different
meaning for the name "width" attach some prefix or suffix to it.
Besides, this way, we can revisit the decision later; it's always
possible to break up a registry in subregistries, but if we have many
registries, with conflicting definitions, it is quite a bit harder to
merge them back together.

On the issue of what formal type to use for the ConstraintSet object, it
seems reasonable to use Object - it's an user-defined object with
somewhat complex internal structure, so Object seems right. (I'll return
to the issue of whether we can use snippets of WebIDL in the prose to
make it clear how this object is to be interrogated by the browser -
again, my personal opinions).

The editors are now hard at work making sure the rest of the document is
consistent with what the document currently says about Constrainable. We
hope to have an updated version with you shortly.

Harald, for the chairs



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Received on Thursday, 6 February 2014 21:57:23 UTC