Re: [xsl] Function to resolve URNs?

["Michael Kay mike@xxxxxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

Unfortunately terminology in this area is very confused and it's best to try
and distinguish:

- expanding a relative reference - this means taking what is popularly called
a relative URI and turning it into an absolute URI, for example index.html
becomes http://www.ibm.com/index.html. This is what the XPath resolve-uri()
function does

- dereferencing a URI - this means taking an absolute URI and fetching the
resource identified by this URI. This may involve

- redirecting a URI - this means taking a URI that doesn't directly identify a
location (for example, a URN) and mapping it to a URI that does identify a
location.

All of these operations, confusingly, are sometimes called "resolving".

If you're starting with a URN, then the first stage (resolving) is irrelevant,
but the "redirecting" stage becomes essential. To redirect a URN to a
dereferenceable URI, you need some kind of catalog that defines the mapping.
This will usually be an "OASIS catalog".

In the Java world, the mechanisms vary a bit depending which API you are
using. For parsers you use an EntityResolver, for transformations you use a
URIResolver, for schemas you might use an LSResourceResolver. There are
various implementations of these interfaces that make use of the data in an
OASIS catalog. This is all generally done outside the XSLT/XQuery code itself,
in the supporting Java (etc) framework.

Michael Kay
Saxonica


> On 13 Jun 2017, at 09:02, Dr. Patrik Stellmann patrik.stellmann@xxxxxxxxx
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hi,
>
> I have files that reference other files and I need to get the URLs of the
files being referenced (e.g. an xsd file including or importing other xsd
files).
>
> I tried to use resolve-uri(@schemaLocation) which works fine for relative
URLs but this does not resolve URNs (which are used in most of my use-cases).
>
> Using base-uri(doc(resolve-uri(@schemaLocation))) works fine (and Ibm
processing the referenced files recursively anyway, so itbs OK for me).
>
> But still Ibm wondering if there isnbt a direct way to resolve the URNs
without having to read the whole file (and also without Saxon-specific
extensions like calling java methods)!?
>
> Thanks and regards,
> Patrik
>
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