SPARQL Aggregation Consensus?

Hi All --

Is there a consensus emerging please on the syntax and semantics* of SPARQL
aggregation over RDF?

If I understand correctly, there are some implementations doing their own
things, but as yet no standard.

If that's indeed the case, is there a timeline for a standard?

Surely, SPARQL should avoid the multi-vendor situation that  SQL got in to
on this matter?

Thanks for educating me about this,    -- Adrian

* Semantics as in, ideally, a model theory that says what the result of any
aggregation must be.

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