Legacy from 1.0: What document properties are preserved/removed by steps in the pipeline

[xml-project]

What document properties are preserved/removed by steps in the pipeline 

This is an aggregation of the discussion on "What document properties are preserved/removed by steps in the pipeline" (Issue 178 of the xproc/1.0-specification)

Opened by: ndw on 2015-06-11, 14:12h

ndw said on 2015-06-11, 14:12h:

No description provided. 

On 2015-06-11, 14:14h: htInEdin was assigned by ndw.

On 2015-10-07, 14:25h: ndw added this to the XProc 2.0 Next PWD milestone.

On 2015-10-07, 15:03h: ndw added the awaiting-proposal label.

[xml-project]

Also see #88 for the general question, which document properties are present at all.

[ndw]

I think this is going to be a hard question, but I also expect it's one that has to be done on a case-by-case basis.

What I want to say is "remove any property that you cannot be certain still applies". But I fear that's going to mean discarding most properties on almost every step. And that greatly reduces the utility of arbitrary properties.

Let's take a few examples. Consider the document "foo.xml" with two properties,base-uri=/foo.xml and user:bar=37.

1. p:identity, both properties flow through unchanged
2. p:xslt, generally speaking, the output from XSLT is something entirely different from the input. So we'd expect the output to have a base-uri property reflective of the base URI of the produced document. It's hard to imagine that you could confidently assign the user:bar property given that you're producing an entirely new document.
3. p:add-attribute, leaves the base-uri property unchanged unless the xml:base attribute was changed! What about user:bar? I don't know. Suppose 37 is the count of the number of attributes and now we've added one?
4. impl:rasterize-image. shrug Who knows?

I fear we're going to have to have some sort of mechanism for pipeline authors to assert which properties should be preserved on an ad hoc basis. Yuck!

[ndw]

We own the default namespace and the p: namespace. Everything else should flow through to the largest extent possible.

[xml-project]

@ndw Close #85 ?

[ndw]

Yes. Per PR #156