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RE: [SUMMARY #1] Why is there little usage of XML on the'vi
Hello Juan,
Juan said:
Yes XML has no concept of multimarkup, but XML people would search a way
to _simulate_ this so much as posible since i think it will become a
fundamental feature when markup languages explosion (i believe that
current 600 XML languages are just the beginning).
Didier replies:
A lot of languages based on XML were developed but few have practical
interpreters associated to them. For instance, CML has several interpreters
able to translate elements of the language into visible objects. XBRL has
several interpreters able to process the language elements into spreadsheets
and more elaborate models (for stock picking). A language based on XML
becomes useful when processors are also provided with it; otherwise it is
only the result of some spare glucose metabolism and not a useful tool :-)
If you count XML based languages having a set of interpreters made available
for public consumption, the number of 600 is reduced to less than 50 (and I
am overly optimist here)
Juan said:
I do not understand you. Yes visually both <p> and <div> are not
differentiable (unless specific styles), but the DOM tree is able to
differentiate both. You can in source-view that both are retained when the
page loaded.
Didier replies:
Juan, the DOM is only an interface to something else. It's an abstraction or
a facet offered for public consumption, it's not the object per se. A DOM is
a public interface but behind the curtain you have something else. For
example, in the Gecko engine, each HTML element is translated (i.e.
interpreted) into a visual object. Idem for IE. Visual objects have several
properties set by either HTML element attributes like for instance the width
or height (when available) or set by CSS properties. Thus, the real object
presenting a DOM interface is a lot more than the DOM. It's a set of methods
and properties some made public like the DOM some made private. It is also
an area laid on a 2D layout, hence the notion of visual object. In the case
of VoiceXML, the result of the interpretation is sound. Hence the notion of
aural objects placed in a time sequence. The real object keeps some
properties like the element tag, this is why we can retrieve its origin. But
also, at least in the case of IE, if you request a serialization of its
current state you'll get all properties attached to the object. The ones
defined as attribute in declarative code (for the browser an HTML document
is declarative code) and the one dynamically attached to the object at
run-time. <div> and <p> inherit from the same "block area" object and the
object inheriting the "block area" features add some properties and methods,
they may be different though even they are both a "block area". The world as
seen by the browser is clearer when seen through its own perspective or the
object oriented perspective. For a browser an HTML element is no longer and
solely an HTML element, it became something else an aggregation of different
things {a visual object, a DOM object, an ECMAScript object, etc...} At
run-time and within a browser an HTML is a lot more than specified at first
in with markups.
Juan said:
Yes, but one is forced to use the available constructs and cannot be
combined and extended. By combined i do not mean a mized datument with
XHTML as host language and MathML and SVH islands in different namespaces
but i explained above with multimarkup and reuse. By extension i mean that
one of ironies of the eXtensible language per excellence today (XML) is
being it does not adressed the extensibility at the client side, only at
the author side. I can extend SVH or HTML inventing new tags but none
browser will understand them. I do not think that was a problem of the
browser community, i think it is one of main design errors of XML.
Didier replies:
XSLT can be perceived as a general purpose XML interpreter. It allows you to
assemble different XML documents into a single one, have different
interpretation strategies for each fragment or vocabulary. For instance, I
can add new vocabularies to an XHTML document and provide an XSLT template
that will use other template/interpreter for other vocabularies I am
including in the XHTML document. This way, the language becomes eXtensible.
Juan said:
Both the Java-plugin and the X3D-like approach may be suitable for
addition of small extensions or semantic layers) over a common basis. In
fact i think that main interest of the CML comunity (I wait prof.
Murray-Rust can correct me if wrong) is in adding the need
funcionality/extensions for the processing of CML units encoded on a host
language, probably XHTML based.
Didier replies:
Could be done and with some help from your community I can bring my modest
contribution.
Juan said:
Interesting! Do you mean some kind of automatic quality-check of the
client browser or what? Someting like the common bottom line in many
sites: this site is better display with ... you need JS enabled ... but in
the heading of the doc.
Didier replies:
Yes this is what I mean. In the last project I was working on for several
years and that was maybe the most ambitious AJAX based project I came to the
conclusion that what is needed in an intelligent interpreter. In many cases,
the system was not responding because the pre-conditions weren't met and no
intelligent message was provided to the users. So I started to display
messages about what the engine is doing, then I still got the same
precondition errors when, for example, the users disabled the javascript
option. So, I am updating the engine with a new algorithm
a) check pre-condition: for example, the very first condition for the engine
to run is to have javascript enable. If not, the engine should display an
error message and a procedure for users to set the javascript to on or make
this site as "trusted". So, not only providing an error message but also
indicating what to do. Same thing if the java VM is disabled, etc... This is
why I came to the conclusion that an environment has to be defined for a
proper interpretation (an interpretation being in my case a rendition).
Based on this definition, the layer provided for the datument can check if
the latter can survive in this host. If not, at least the user is made aware
of what is wrong and what to do.
Cheers
Didier PH Martin
http://didier-martin.com
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