Re: The semantics of mediaobject

I agree with Bob=E2=80=99s point. There=E2=80=99s no reason you can=E2=80=99=
t transform into a format for software that can handle multiple formats =
and let the rendering software figure out what to do.

In fact, that already happens in the XSL 1.0 version of the stylesheets. =
If you have a mediaobject that contains an image or video, and you =
include a <textobject> that contains a <phrase>, the contents of the =
phrase are used as alternate text in the html. I use that all the time =
(thanks for implementing that, Bob).

If the browser decides there=E2=80=99s a good reason to render both at =
the same time (e.g., having a button that lets you display the alt text =
over or next to an image), that seems reasonable to me.

That said, it might be good to adjust the description of mediaobject to =
not be so definite in its ruling out of the option.

I also wonder whether the use of <textobject><phrase> for alt text =
should be made an official part of the specification.

Dick
-------
XML Press
XML for Technical Communicators
http://xmlpress.net
[email protected]



> On Apr 5, 2023, at 14:00, Bob Stayton <[email protected]> wrote:
>=20
> It seems ok to me.  The idea of a mediaobject is to contain markup for =
one or more versions of the same content.  Presenting more than one of =
those to the end user would be redundant and annoying.  If you consider =
the whole rendering system to be the transformation from DocBook to =
HTML5 *and* the browser rendering of that HTML5, then your use case does =
not seem to violate the description because the consumer of the content =
sees only one version, right?
>=20
> Bob
>=20
> On 4/5/2023 9:27 AM, Norm Tovey-Walsh wrote:
>> Hello world,
>>=20
>> The description of mediaobject states:
>>=20
>>   This element contains a set of alternative =E2=80=9Cmedia =
objects.=E2=80=9D Exactly
>>   one object will be selected and rendered. =E2=80=A6 Under no =
circumstances
>>   should more than one object in a mediaobject be used or presented =
at
>>   the same time.
>>=20
>> Bearing in mind that this markup was invented 15 or 20 years ago, =
long
>> before any (widely used) web browser offered anything sophisticated =
in
>> the way of fallback, we anticipated that markup like this:
>>=20
>>   <mediaobject>
>>     <videoobject>=E2=80=A6</videoobject>
>>     <imageobject>=E2=80=A6</imageobject>
>>     <textobject>=E2=80=A6</textobject>
>>   </mediaobject>
>>=20
>> would be intepreted along the following lines: =E2=80=9C=E2=80=A6 a =
mediaobject might
>> contain a video, a high-resolution image, a low-resolution image, a =
long
>> text description, and a short text description. In a =E2=80=98high-end=E2=
=80=99 online
>> system, the video is used. For print publishing, the high-resolution
>> image is used. For other online systems, either the high- or the
>> low-resolution image is used, possibly including the short text
>> description as the online alternative. In a text-only environment,
>> either the long or the short text description is used.=E2=80=9D
>>=20
>> <aside>I observe that =E2=80=9Cpossibly including the short text=E2=80=9D=
 is, by a very
>> narrow reading, a violation of the semantics we=E2=80=99ve already
>> asserted.</aside>
>>=20
>> Starting in V5.1 we allow more than one *data element in a *object
>> element[1] with the semantics that the downstream processor will pick
>> one. So now you can do:
>>=20
>>   <mediaobject>
>>     <videoobject>
>>       <videodata type=3D"video/mp4" =E2=80=A6/>
>>       <videodata type=3D"video/webm" =E2=80=A6/>
>>     </videoobject>
>>     <imageobject>=E2=80=A6</imageobject>
>>     <textobject>=E2=80=A6</textobject>
>>   </mediaobject>
>>=20
>> And let the browser decide whether it wants to render MP4 or WebM.
>>=20
>> Trouble is, you can=E2=80=99t put imagedata in the videoobject =
wrapper, so
>> there=E2=80=99s no way to fallback to a still image. We could fix =
this by
>> changing videoobject (and audioobject) to allow imageobject, but at =
that
>> point, we might as well do away with the various flavors and just =
have
>> one wrapper. (That=E2=80=99s probably what we=E2=80=99d do today, if =
we were starting
>> over.)
>>=20
>> Rather than make the markup even more complicated, I=E2=80=99m =
tempted to squint
>> really hard at the semantics and try to persuade you that selecting
>> multiple objects from the same mediaobject is not a violation of the
>> semantics if the rendering system will only render one of them.
>>=20
>> In other words, I want a license to cheat and say that I can render =
that
>> example above in HTML5 as a video element containing three sources, =
two
>> videos and an image. What say you?
>>=20
>>                                         Be seeing you,
>>                                           norm
>>=20
>> [1] But the content model of imageobject weirdly forbids you from =
mixing
>> SVG and MathML and other formats. What is that about?
>>=20
>> --
>> Norm Tovey-Walsh=20
>> <[email protected]>
>> https://norm.tovey-walsh.com/
>>=20
>>=20
>>=20
>>> Advancement is powered by the dynamic interaction of theory and
>>> practice.
>>>=20