Re: [Caml-list] ocamlnet: Netheml: simple-dtd: how does this work?

[oliver <oliver@first.in-berlin.de>]

On Mon, Mar 07, 2011 at 03:44:15PM +0100, oliver wrote:
> On Mon, Mar 07, 2011 at 02:40:37PM +0100, Gerd Stolpmann wrote:
> > Am Montag, den 07.03.2011, 13:57 +0100 schrieb oliver:
> > > On Mon, Mar 07, 2011 at 01:27:55PM +0100, Gerd Stolpmann wrote:
> > > > Am Sonntag, den 06.03.2011, 23:52 +0100 schrieb oliver:
> > > > > Hello,
> > > > > 
> > > > > tried around using the simple-dtd argument
> > > > > for Nethtme.parse.
> > > > > 
> > > > > It changes the behaviour compared to
> > > > > the default behaviour, but I could not find out
> > > > > how this works.
> > > > > 
> > > > > Someone here who can explain me this
> > > > > argument and describe, how it can be used?
> > > > 
> > > > Maybe the HTML specification would be a good reference here:
> > > > http://www.w3.org/TR/1999/REC-html401-19991224. You will see there that
> > > > most HTML elements are either an inline element, a block element, or
> > > > both ("flow" element). The grammar of HTML is described in terms of
> > > > these classes. For instance, a P tag (paragraph) is a block element and
> > > > contains block elements whereas B (bold) is an inline element and
> > > > contains inline elements. From this follows that you cannot put a P
> > > > inside a B: <B><P>something</P></B> is illegal.
> > > > 
> > > > The parser needs this information to resolve such input, i.e. do
> > > > something with bad HTML. As HTML allows tag minimization (many end tags
> > > > can be omitted), the parser can read this as: <B></B><P>something</P>
> > > > (and the </B> in the input is ignored).
> > > > 
> > > > If all start and all end tags are written out, changing the
> > > > simplified_dtd does not make any difference.
> > > > 
> > > > There is no normative text that says how to read bad HTML. Because of
> > > > this, it is - to a large degree - an interpretation of HTML what you put
> > > > into simplified_dtd.
> > > > 
> > > > > The description IMHO is not sufficient to explain
> > > > > this feature.
> > > > 
> > > > I'd say your formal knowledge about HTML is insufficient.
> > > [...]
> > > 
> > > If formal HTML spec is sufficient to know the behaviour of the module,
> > > there would no need to have the dtd-argument, which seems, follwoinjg your
> > > explanations, to change the behavior in a way that it does NOT follow
> > > the formal specifications.
> > 
> > There is no standard regarding that (except that HTML is also SGML, and
> > there are some rules for that in SGML). You could also reject bad HTML.
> > But this has not become common practice (unlike for XML, for instance).
> > 
> > So, it depends on your HTML documents how you want to fix bad HTML.
> > That's the reason why you can configure it.
> [...]
> 
> But it's not mentioned how the dtd-Argument works.
[...]


For example, if you use the empty string "" as a tag,
it changes the parsing behaviour, even I doubt there is a tag
that has "" as name.

The same problem occurs with any phantasy-tag.

If I change non existing tags, why does the module parse correct html
different when using such a dtd-arg, compared to not using the dtd-arg?

I doubt I can find the answer in the HTML-spec.

Ciao,
   Oliver