[dsdl-discuss] Re: Part 10 Scenario

XPL has a lot in common with my Schemachine proposal
  http://www.topologi.com/resources/pdfs/Schemachine.pdf

Both are pipelines, with input and output and top-level params.
Both seem to work strictly XML in/XML out.

XPL provides for parameters using the same mechanism as inputs,
Schemachine has a separate element. No big difference.

Schemachine provides mechanisms for supporting passes, and
phases. XPL does not seem to have a mechanism for allowing the
failure of one stage to abort or cause the subsequent validation
of other stages.

XPL has a selection mechanism, for-each, which schemachine does
not. If this were limited to a streaming untyped subset of Xpath,
this would be a good addition.

XPL allows inline documents/data. This seems a good innovation.

So my take is that XPL has some worthwhile marginal improvements on
Schemachine but is basically the same thing. However, it
needs specific mechanisms to allow the results of one validation
to influence subsequent steps (such as the grouping of phases
and passes in Schemachine) to be as useful. The difference between
a validation pipeline and a processing pipeline is that
for validation pipelines are constructed so that a valid document
is the *exception* case rather than the target case IYSWIM:
locating problems then detecting their cause and diagnosing the
fix is the purpose of the pipeline.

Cheers
Rick Jelliffe

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