Legacy from 1.0: 3.5 Provide a mechanism for importing user-defined functions

[xml-project]

3.5 Provide a mechanism for importing user-defined functions 

This is an aggregation of the discussion on "3.5 Provide a mechanism for importing user-defined functions" (Issue 49 of the xproc/1.0-specification)

Opened by: ndw on 2014-08-22, 18:39h

ndw said on 2014-08-22, 18:39h:

Experience with user-defined functions in XQuery and XSLT reveals that they can be a powerful addition to the language. Providing some feature that allowed users to extend the vocabulary of functions available in, for example, the test expressions on p:when elements would greatly simplify some pipelines. 

Such a mechanism might take the form of the ability to load extension functions defined in, for example, XQuery, or it might include adding the ability to define functions in XProc. 

On 2014-08-22, 18:39h: ndw added requirement should labels.

On 2014-08-25, 22:28h: ndw added this to the XProc 2.0 LC milestone.

ndw said on 2015-03-19, 11:50h:

It would be useful to be able to add user-defined functions to XProc. XProc steps themselves don't immediately lend themselves to this task because there's not a completely obvious mapping between step signatures and function signatures. However, most XProc engines are going to have access to XSLT and/or XQuery engines and both of those languages have a built-in mechanism for creating functions. 

This proposal is for ap:import-functionselement that can import externally-defined functions from languages such as XQuery or XSLT. 

This element instruct the XProc processor to load external functions from the specified library. It is a static error if the processor cannot access the URI or if the URI points to a format that the implementation does not recognize. 

Thenamespaceattribute specifies the namespace in which the imported functions must reside. It is a static error if the specified URI does not define functions in that namespace. 

Thetypeattribute specifies the expected type of the content. Implementations should supportapplication/xslt+xmlandapplication/xqueryfor XSLT and XQuery implementations. Support for other formats is impelementation-defined. 

On 2015-06-11, 08:57h: ndw added the proposed-resolution label.

On 2015-10-07, 15:02h: ndw modified the milestone: XProc 2.0 Next PWD, XProc 2.0 LC.

[xml-project]

See also #10

[xml-project]

See issue #10

[xml-project]

At Prague 2018 we decided to have a new element like
<p:import-functions href="foo.xsl" type="application/xslt+xml" namespace="http://example.com/foo"/>.

See minutes, day 1

[xatapult]

If I remember correctly we decided on:

• Whether p:import-functions is supported (and what it can import) is implementation defined
• Global variables are not imported (Think about import of variables from xslt- and xquery packages #292)
• A p:import-functions can appear everywhere a p:import can appear

There is however no mention of p:import-functions yet in the spec. So this remains to be done.

But am I correct that we have consensus on the three points mentioned above?

[xml-project]

But am I correct that we have consensus on the three points mentioned above?

Yes,
Yes and
Yes