[xsl] import, include, and packages?

Subject: [xsl] import, include, and packages?
From: "David Birnbaum djbpitt@xxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>
Date: Thu, 23 Apr 2020 15:36:56 -0000
Dear XSL-list,

I find myself writing my first importable XSLT function since the advent of
XSLT 3.0, and I would be grateful if someone could advise me about best
practicebor, at least, about pitfalls of which I should be aware.

In the past I have used <xsl:include> and <xsl:import> pretty much
arbitrarily. I understand that imported templates have lower priority, but
in my environment I don't need to deal with competing priorities, so I have
not seen a reason to prefer one of these over the other. If I am
overlooking a reason to prefer one or the other when priorities aren't an
issue, I would be grateful for advice.

Since <xsl:package> is now available, I thought this was an opportunity to
learn how to use it. I have read Michael Kay's
http://www.xmlamsterdam.com/pdf/2013/2013-michaelhkay-ansterdam.odp, the
Saxon documentation for <xsl:package> and <xsl:use-package>, and the
corresponding sections of the XSLT 3.0 spec. I am not confident that I have
understood all of these fully. In particular:

1. I think the advantage of using <xsl:package> over <xsl:import> and
<xsl:include> for my case (importing a single function [but see below about
arity]], from a package that does not import anything itself) is that I can
expose only the function that I want to expose, and not any other named
components of the imported package (variables, helper functions, etc.). If
that understanding is correct, it does sound like an advantage. (I want to
be able to run the code in Saxon HE, so being able to precompile the
package, which would be a benefit under other circumstances, would not be
relevant in this case.)

2. I don't understand how (or whether it is possible) to import packages
without setting up a configuration file. If it isn't, that would seem to be
a disadvantage for my use case, since anyone else who wanted to use my
function library would have to set up a configuration, as well., and not
just get a copy of the package file itself If I have understood correctly,
the spec seems to say that the configuration is implementation-dependent,
so if one is needed, where would I find documentation about how to set it
up for use by Saxon, both at the command line and inside <oXygen/>? If a
configuration setup is not requiredbthat is, if it is possible to specify
the file-system location of the imported package directly inside the
importing oneb how do I specify the location of the imported package in
<xsl:use-package>, given that I would want the path to be relative to the
importing stylesheet? Is the procedure for doing that the same as with
<xsl:include> and <xsl:import>?

3. On a semi-related topic, I want my function to have one-argument and
two-argument versions. Since function parameters cannot be optional, I
think a fairly straightforward way to do this would ge to put the code in
the two-argument version, and have the one-argument version supply a
default for the missing argument and then use it to pass the call along to
the two-argument version. Is this the best way to deal with optional
function arguments?

Thank you all for any advice or guidance you might be able to provide.



David J. Birnbaum, dbpitt@xxxxxxxxx

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