Can somebody clarify how to use content-type specifiers in href links.
I've spent quite some time looking for information in various HTML
specification places, such as 3w, but can't quite find the right info.

Some (most?) mime types have no parameters, for example:
href="filename.zip" type="application/zip"

Some have extra parameters. Specifically, application/riscos is:
content-type application/riscos
type=string
load=&xxxxxxxx
exec=&xxxxxxxx
attr=&xx

see http://www.mdfs.net/Docs/Internet/Mime/riscos.htm

How do I specify that within an href link?  I would assume:
href="filename" type="application/riscos load=&ffffed4c exec=&33746fe2
attr=&3b"

I can't find any explicit clarification anywhere, so I hoped that the
collected wisdom here might know.

Thanks.

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"J.G.Harston" <jgh@arcade.demon.co.uk> wrote:

> Can somebody clarify how to use content-type specifiers in href links.
> I've spent quite some time looking for information in various HTML
> specification places, such as 3w, but can't quite find the right info.
>
> Some (most?) mime types have no parameters, for example:
> href="filename.zip" type="application/zip"
>
> Some have extra parameters. Specifically, application/riscos is:
> content-type application/riscos
> type=string
> load=&xxxxxxxx
> exec=&xxxxxxxx
> attr=&xx
>
> see http://www.mdfs.net/Docs/Internet/Mime/riscos.htm
>
> How do I specify that within an href link?  I would assume:
> href="filename" type="application/riscos load=&ffffed4c exec=&33746fe2
> attr=&3b"
>
> I can't find any explicit clarification anywhere, so I hoped that the
> collected wisdom here might know.

There's no need to specify the file type you are linking to.

If you're linking to something exotic like a PDF, make sure to tell your
readers first.
--
Michael Wilcox
http://mikewilcox.t35.com

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In article <KULc9.3424$6i4.236783@newsread1.prod.itd.earthlink.net>, one of infinite monkeys
	at the keyboard of "Michael Wilcox" <nospam@nospam.com> wrote:
 
> There's no need to specify the file type you are linking to.

True, but it might help a smart user agent to know whether it's interested
in the link.  No harm in it.

The syntax would be the same as in the (mandatory) Content-Type header
in every HTTP transaction, as noted by someone else.

-- 
Nick Kew

Available for contract work - Programming, Unix, Networking, Markup, etc.

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and then J.G.Harston said:
>
> How do I specify that within an href link?  I would assume:
> href="filename" type="application/riscos load=&ffffed4c exec=&33746fe2
> attr=&3b"

Nearly.  You just need a semicolon:

<a href="foo" type="text/plain; charset=US-ASCII">

For info see rfc822  - http://google.com/search?q=rfc822

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jgh@arcade.demon.co.uk (J.G.Harston) wrote:

> Can somebody clarify how to use content-type specifiers in href links.

In the HTML specification, this is discussed at
http://www.w3.org/TR/html4/struct/links.html#adef-type-A
Note that it says: "Authors who use this attribute take responsibility to 
manage the risk that it may become inconsistent with the content available at 
the link target address." And on the practical side, I wonder if any browser 
or other generally used program actually makes any use of type attributes in 
<a href> at present.

> Some (most?) mime types have no parameters, for example:
> href="filename.zip" type="application/zip"

The description of each media type specifies whether it may have parameters, 
what the parameters can be and whether they are required. For 
application/zip, for example, there are no parameters. The descriptions of 
the officially registered types can be found via the official registry:
ftp://ftp.isi.edu/in-notes/iana/assignments/media-types/
For media types (MIME types) in general, there is a compilation of relevant 
RFCs at
http://www.oac.uci.edu/indiv/ehood/MIME/MIME.html

> Some have extra parameters. - -
> How do I specify that within an href link?  I would assume:
> href="filename" type="application/riscos load=&ffffed4c exec=&33746fe2
> attr=&3b"

The "media type" concept is not crystal clear in HTML, and the examples 
mentioned have no parameters. But in MIME specifications, parameters, if 
present, are considered as part of the media type denotation, and they are 
written after the type name, so that a semicolon precedes each attribute. 
When writing them in HTML, normal HTML rules (e.g. regarding the "&" 
character) need to be applied. So you would use
type="application/riscos;load=&amp;ffffed4c;exec=&amp;33746fe2;attr=&amp;3b"

But it's debatable whether it's of practical use. In any case, it must not be 
regarded as a substitute for making the server send adequate HTTP headers 
when responding to a request for the linked resource.

-- 
Yucca, http://www.cs.tut.fi/~jkorpela/
Pages about Web authoring: http://www.cs.tut.fi/~jkorpela/www.html

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"Jukka K. Korpela" <jkorpela@cs.tut.fi> exclaimed in <Xns927DEB12831F3jkorpelacstutfi@193.229.0.31>:

> the link target address." And on the practical side, I wonder if any browser 
> or other generally used program actually makes any use of type attributes in 
> <a href> at present.

  Whether it is of practical use I cannot say: Mozilla does indeed report
  this if you ask for the properties of a link.

-- 
 -    Tina Holmboe                    Greytower Technologies
   tina@greytower.net                http://www.greytower.net/
   [+46] 0708 557 905

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"Jukka K. Korpela" <jkorpela@cs.tut.fi> wrote:

> And on the practical side, I wonder if any browser 
> or other generally used program actually makes any use of type attributes in 
> <a href> at present.

Just a thought: if CSS attribute selectors are supported, a user style
sheet could be used to highlight desirable/undesirable links to
various content types.  That might be marginally practical.

--
Greg Recco

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In message <b1719e4d.0209031157.3336307b@posting.google.com>, Greg Recco 
<gwr5@psu.edu> writes
>Just a thought: if CSS attribute selectors are supported, a user style
>sheet could be used to highlight desirable/undesirable links to
>various content types.  That might be marginally practical.

That could be a fun idea - how about using CSS to add an icon depicting 
the type after the link, for example PDF links could be made more 
obvious without interrupting the HTML with marginally important IMG 
elements.

-- 
Gg

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George Lund <george@lundbooks.co.uk> wrote:

> That could be a fun idea - how about using CSS to add an icon depicting 
> the type after the link, for example PDF links could be made more 
> obvious without interrupting the HTML with marginally important IMG 
> elements.

It could be more than fun, for example in situations where PDF format is 
especially useful. Or, to take a different view, particularly useless, in 
which case the user might even wish to _suppress_ any information about any 
PDF resources.

Anyway, it works best when done by the user, or for the user by someone who 
helps him. The author would just use type attributes that give adequate 
information, and leave it at that. But I would recommend doing so
_in addition_ to making a textual note (minimally, "(PDF)") about the format.

-- 
Yucca, http://www.cs.tut.fi/~jkorpela/
Pages about Web authoring: http://www.cs.tut.fi/~jkorpela/www.html

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"Jukka K. Korpela" <jkorpela@cs.tut.fi> wrote in message news:<Xns927DEB12831F3jkorpelacstutfi@193.229.0.31>...
> When writing them in HTML, normal HTML rules (e.g. regarding the "&" 
> character) need to be applied. So you would use
> type="application/riscos;load=&amp;ffffed4c;exec=&amp;33746fe2;attr=&amp;3b"

Thanks, very useful.

> But it's debatable whether it's of practical use. In any case, it must not be 
> regarded as a substitute for making the server send adequate HTTP headers 
> when responding to a request for the linked resource.

Until I host my site on a server that knows about the RISC OS
metadata, the server won't know about the metadata, and so won't send
it in an HTTP header. (I haven't investigated fully, but it probably
sends an incorrect header, probably text/plain.) Until then, href
links in documents on my site that point to files that have RISC OS
metadata having a specified content type will allow user agents that
understand it to use the supplied metadata. If/when I host my site on
a server that understands RISC OS metadata, the server will send
correct HTTP headers, and the content type in the href links will
become redundant, but useful backups.

JGH

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