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> IMO, from another view, if we have the pipeline idea, there is not
> that much difference of transformer and publisher, except the
> publisher will end the pipeline. 

... and know how to interface with an external conduit in a generic
way (whereas the transformers would tend to be much more specific
to a particular measurement).

> Every components in the pipeline simply passing the data down the
> pipeline, and the next item in the pipeline decide continue, or publish.

Yep, transformers should be chainable and capable of discarding
(either by explicitly calling down the chain, or by signalling a
stopping condition in some other way, e.g. raise an exception
or return False or whatever makes sense as a protocol).

Cheers,
Eoghan