Re: Nested entity declarations in DTDs
David Carlisle <[email protected]>
| Newsgroups | gmane.text.xml.devel |
|---|---|
| Message-ID | <CAEW6iOjOCnAcDJLnjzQ=pVzTrLn0Pj9_vzog7Xi3r+Gj0TqUww@mail.gmail.com> |
On Sun, 13 Mar 2022 at 16:59, <[email protected]> wrote: Hi David, > > Thanks for the reply! So the behaviour can change based on whether its > internal or external? That is very good to know now before I back myself > into a corner with the implementation. > > Is there a reason for that? "Why" questions are hard to answer, especially when there are people watching who were there and could answer:-) But I think that the idea was that processors are allowed to not fetch external subsets but are required to process the internal subset so the internal subset has a restricted syntax so that such implementations don't need the full weirdness power of full DTD processing capability. David > I was naively hoping that external DTDs could be more or less pulled into > the start of the document and carry on as normal. > > Regards > > Daniel > > On 13 Mar 2022, 16:28 +0000, David Carlisle <[email protected]>, > wrote: > > You can have the definitions but you can't reference them as you can't > have parameter entity references in the internal subset, rxp moans: > > $ rxp -sx nes1.xml > Error: PE ref not allowed here in internal subset > in entity "g" defined at line 19 char 1 of file:///c:/tmp/nes1.xml > in unnamed entity at line 23 char 4 of file:///c:/tmp/nes1.xml > > > > If on the other hand you do this in an external DTD it is fine > > <?xml version="1.0" encoding="utf-8"?> > <!DOCTYPE feed SYSTEM "nest1.dtd"> > > <feed xmlns="&a;">&b;</feed> > > where nest1.dtd is > > <!ENTITY a 'http://www.w3.org/2005/Atom'> > <!ENTITY b '&e;&f;&g;&h;&i;'> > <!ENTITY c 'tag:xn--8ws00zhy3a.com,2006-05-04:/tests/atom/obfuscated/'> > <!ENTITY d 'http://www.xn--8ws00zhy3a.com/tests/atom/obfuscated/'> > <!ENTITY e '<title>Obfuscated Atom</title> > <updated>2007-10-19T00:00:00+00:00</updated> > <id>&c;</id><link rel="alternate" href="&d;"/> > <link rel="self" href="&d;1_4.atom"/> > <author><name>James Holderness</name></author>'> > <!ENTITY % a '<entry><title>This is title #'> > <!ENTITY % b '</title><updated>2007-10-18T23:'> > <!ENTITY % c ':00+00:00</updated><id>&c;'> > <!ENTITY % d '</id><link href="&d;'> > <!ENTITY % e '.html"/><summary type="html"> > This is the <code>summary</code> for entry number '> > <!ENTITY % f '.</summary></entry>'> > <!ENTITY % g '<!ENTITY f > "%a;1%b;59%c;1%d;1%e;1%f;">'> > <!ENTITY % h '<!ENTITY g > "%a;2%b;58%c;2%d;2%e;2%f;">'> > <!ENTITY % i '<!ENTITY h > "%a;3%b;57%c;3%d;3%e;3%f;">'> > <!ENTITY % j '<!ENTITY i > "%a;4%b;56%c;4%d;4%e;4%f;">'> > %g;%h;%i;%j; > > > produces: > > > > $ rxp -x nes1.xml > <feed xmlns="http://www.w3.org/2005/Atom"><title>Obfuscated > Atom</title> <updated>2007-10-19T00:00:00+00:00</updated> <id>tag: > xn--8ws00zhy3a.com,2006-05-04:/tests/atom/obfuscated/</id><link href=" > http://www.xn--8ws00zhy3a.com/tests/atom/obfuscated/" > rel="alternate"></link> <link href=" > http://www.xn--8ws00zhy3a.com/tests/atom/obfuscated/1_4.atom" > rel="self"></link> <author><name>James > Holderness</name></author><entry><title>This is title > #1</title><updated>2007-10-18T23:59:00+00:00</updated><id>tag: > xn--8ws00zhy3a.com,2006-05-04:/tests/atom/obfuscated/1</id><link href=" > http://www.xn--8ws00zhy3a.com/tests/atom/obfuscated/1.html"></link><summary > type="html"> This is the <code>summary</code> for entry number > 1.</summary></entry><entry><title>This is title > #2</title><updated>2007-10-18T23:58:00+00:00</updated><id>tag: > xn--8ws00zhy3a.com,2006-05-04:/tests/atom/obfuscated/2</id><link href=" > http://www.xn--8ws00zhy3a.com/tests/atom/obfuscated/2.html"></link><summary > type="html"> This is the <code>summary</code> for entry number > 2.</summary></entry><entry><title>This is title > #3</title><updated>2007-10-18T23:57:00+00:00</updated><id>tag: > xn--8ws00zhy3a.com,2006-05-04:/tests/atom/obfuscated/3</id><link href=" > http://www.xn--8ws00zhy3a.com/tests/atom/obfuscated/3.html"></link><summary > type="html"> This is the <code>summary</code> for entry number > 3.</summary></entry><entry><title>This is title > #4</title><updated>2007-10-18T23:56:00+00:00</updated><id>tag: > xn--8ws00zhy3a.com,2006-05-04:/tests/atom/obfuscated/4</id><link href=" > http://www.xn--8ws00zhy3a.com/tests/atom/obfuscated/4.html"></link><summary > type="html"> This is the <code>summary</code> for entry number > 4.</summary></entry></feed> > > On Sun, 13 Mar 2022 at 15:40, <[email protected] > <https://mailto:[email protected]>> wrote: > > Hello all, > > I was wondering if anyone could help clarify an aspect of the > specification for DTDs; I am currently working on an XML parser, but have > never really used DTDs myself. > > http://www.詹姆斯.com/blog/2007/10/obfuscated-atom > <http://www.xn--8ws00zhy3a.com/blog/2007/10/obfuscated-atom> > In the above URL, there is a DTD (copied below) with nested entity > declarations, is this valid? > > <?xml version="1.0" encoding="utf-8"?><!DOCTYPE feed [<!ENTITY a 'http://www.w3.org/2005/Atom'><!ENTITY b '&e;&f;&g;&h;&i;'><!ENTITY c 'tag:xn--8ws00zhy3a.com,2006-05-04:/tests/atom/obfuscated/'><!ENTITY d 'http://www.xn--8ws00zhy3a.com/tests/atom/obfuscated/'><!ENTITY e '<title>Obfuscated Atom</title> <updated>2007-10-19T00:00:00+00:00</updated> <id>&c;</id><link rel="alternate" href="&d;"/> <link rel="self" href="&d;1_4.atom"/> <author><name>James Holderness</name></author>'><!ENTITY % a '<entry><title>This is title #'><!ENTITY % b '</title><updated>2007-10-18T23:'><!ENTITY % c ':00+00:00</updated><id>&c;'><!ENTITY % d '</id><link href="&d;'><!ENTITY % e '.html"/><summary type="html"> This is the <code>summary</code> for entry number '><!ENTITY % f '.</summary></entry>'><!ENTITY % g '<!ENTITY f "%a;1%b;59%c;1%d;1%e;1%f;">'><!ENTITY % h '<!ENTITY g "%a;2%b;58%c;2%d;2%e;2%f;">'><!ENTITY % i '<!ENTITY h "%a;3%b;57%c;3%d;3%e;3%f;">'><!ENTITY % j '<!ENTITY i "%a;4%b;56%c;4%d;4%e;4%f;">'>%g;%h;%i;%j;]><feed xmlns="&a;">&b;</feed> > > > > Saxon and the XSLT processor in Chrome both say no, but if you try the > processor in Firefox it appears to process fine. > > http://xsltfiddle.liberty-development.net/jy6KM8g > Any pointers in the right direction would be appreciated, many thanks in > advance. :) > > Regards > > Daniel > >