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   RE: [xml-dev] What is coupling? [Was: 3 XML Design Principles] [T2005020

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On February 1 2005 at 14:13:43 EST Bullard, Claude L (Len) <len.bullard@intergraph.com> wrote:
> No, I'd say you are getting it.  XML Doesn't Care.
> It is just structured/named data.  There are some
> wrinkles to how that works determined by the context of
> use (system rules).
> Modules (even XSLT) that use XML do care.  The
> appropriate structure depends on the module. That
> is why we brought up USE nodes.  It's not just
> a pointer; it is what is done with the thing pointed
> to; in the case of a use node, it is copied on
> render but is one data structure in memory.  For
> that application, pointing is faster than having
> a duplicate.  In X3D, deep nesting slows down
> the application.  Put a lot of named primitives
> (spheres, boxes, etc.) into a scene and nest them,
> and the frame rate will drop to sub 4fps rates;
> say, crawls.  Good authoring systems enable this
> to be optimized and flattened into more efficient
> representations like indexed face sets.  The cost:
> it's a one way conversion because information is lost.
> The gain: fidelity to real time.
> A more interesting coupling/cohesion study might
> be the effect of certain kinds of standards for
> schema development.  For example, the UBL
> naming standard is itself, 112 pages long.
> That ripples across a lot of other standards.
> Is coupling to that enhancing the cohesion of
> the standards that couple to it?
> len
> From: Robert Koberg [mailto:rob@koberg.com]
> Bullard, Claude L (Len) wrote:
> > Cohesion and coupling:
> ....
> > and of course, the ultimate expression of homophilic principles, the Law
> of
> > Demeter:
> > "Only talk to your friends."  For programmers, there are lots of articles
> on
> > this one.
> >
> > http://www.cmcrossroads.com/bradapp/docs/demeter-intro.html
> I am having trouble applying OO to XML, but I read this from the above
> article:
> "The Law of Demeter says that if I need to request a service of an
> objects sub-part, I should instead make the request of the object itself
> and let it propagate this request to all relevant sub-parts, thus the
> object is responsible for knowing its internal make-up instead of the
> method that uses it."
> To me, if I have a nested structure in an XML instance and using XSL on
> that I apply-templates (flow through the instance doc) and only do what
> is in the XML. If I come across something that is a reference to
> something else I can go out, get it, apply-templates on it and continue
> where I left off.
> If I have a flat structure in an instance doc I have to assume where
> things go and place them in a more rigid way.
> Am I just not getting it?
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