Re: question on p:directory-list and base-uri()

Hello,

Like Frank, I was reminded of something back in the day ... for me it
raised old ghosts of relative links in a site produced by Apache Cocoon ...
pattern matching in Cocoon sitemaps?

At any rate, Norm's analysis and conclusion sound right to me, including
the wrinkly part. (Call it 'pleated'?)

Regards, Wendell

On Wed, Feb 26, 2025 at 10:30 AM Frank Steimke <fsteimke.hb@gmail.com>
wrote:

> Hi Norm,
> It reminds me of a Bug Report many  years ago (2013 actually). A Bug in
> Saxon was suspected. See
> https://www.oxygenxml.com/forum/topic9194.html
> dont know if your System has Access to very old issues. It would be
> interesting to check relationship to the current issue …
>
> Greetings, Frank
> Norm Tovey-Walsh <ndw@nwalsh.com> schrieb am Mi. 26. Feb. 2025 um 09:47:
>
>> Hello,
>>
>> I think I’ve worked out what’s going wrong and a simple fix. There are
>> still some interesting wrinkles though.
>>
>> Given this document and @select="//c:directory/c:directory":
>>
>> <c:directory xmlns:c="http://www.w3.org/ns/xproc-step"
>>              xml:base="file:/tmp/y/"
>>              name="y">
>>    <c:file xml:base="file" name="file"/>
>>    <c:directory xml:base="z/" name="z">
>>       <c:file xml:base="file" name="file"/>
>>    </c:directory>
>> </c:directory>
>>
>> My implementation uses the select expression to locate the relevant
>> nodes. This one:
>>
>>    <c:directory xml:base="z/" name="z">
>>       <c:file xml:base="file" name="file"/>
>>    </c:directory>
>>
>> And then it constructs a document containing that node. It constructs an
>> XML document. What’s the base URI of *that* document?
>>
>> Well, the wrong answer is, the same as its root element. Because that
>> gives you a document with the base URI “file:/tmp/y/z/” that has a root
>> element with an xml:base attribute of “z/” and bad happens.
>>
>> (If the root element doesn’t have an xml:base attribute, surely the 99%
>> case in general, or it has an xml:base that’s an absolute URI, no problem
>> arises.)
>>
>> One way to resolve this would be to remove the xml:base attribute from
>> the root element in this case. If we’d said that from the beginning of
>> XProc 1.0, then users would just be living with it. But I think saying it
>> now would be pretty hostile.
>>
>> The only other option (that I can think of) is to change the base URI of
>> the *document* so that when the xml:base attribute is applied, the right
>> thing happens.
>>
>> I spent a few minutes pondering all of the complexity involved in taking
>> an absolute URI and a relative xml:base and working out how to manipulate
>> the absolute URI so that it was what you’d need to start with to get back
>> the original when you applied the xml:base. The simple case, and you always
>> get the simple case from p:directory-list, is easy. But users can put
>> arbitrary values in xml:base attributes.
>>
>> What do you do to “file:/tmp/y/z/” to make it the “before URI” if the
>> xml:base attribute is “./spoon/../../x/y/test/”?
>>
>> And then it occurred to me that the base URI of the element’s *parent* is
>> *necessarily* the right value. The actual base URI of the element in
>> question was literally constructed by applying its xml:base attribute value
>> to the parent’s base URI.
>>
>> We’re left with the wrinkle that the base URI of the *XML document* is
>> going to be different (is going to be the base URI of the selected
>> element’s parent) from the base URI of the document element in this case.
>>
>> I can imagine that might be a little surprising, but I think it’s
>> justified in order to avoid producing utterly the wrong base URI on the
>> document element.
>>
>> I’ve constructed a few tests and I’ve just thought of one more that I
>> should write.
>>
>>                                         Be seeing you,
>>                                           norm
>>
>> --
>> Norm Tovey-Walsh <ndw@nwalsh.com>
>> https://norm.tovey-walsh.com/
>>
>> > To see the world in a grain of sand,/And a heaven in a wildflower,/Hold
>> infinity in the palm of your hand/and eternity for an hour.--William Blake
>>
>>

-- 
...Wendell Piez... ...wendell -at- nist -dot- gov...
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