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hi roger,
i think you've got the thrust of your argument wrong. symbols, whatever
they are, and syntax if it exists (actually it must exist for the symbol
to be other than random noise) are just that. outside of the system that
processes them they are meaningless. and the processing system can
choose to interpret them any way it wants. apply that to archeology,
paleontology, pschology, and the so called soft sciences........ but i
digress.
the xml can state explicit relationships because that's how my
processing system chooses to process the xml. the fact that xml is good
at representing so many things is why there are so many processing
systems. at this stage it's difficult to discuss one without the other.
the original discussion was more valuable - is xml up to the task of
representing the relationships? not is it implicit in xml.
your arguments can be applied to all manner of things, but the use of
symbololgy is key to the success of human beings. xml is another
symbology to be used, abused, and processed.
my thoughts....
rick
Roger L. Costello wrote:
>Hi Folks,
>
>This past week we discussed implicit versus explicit relationships.
>This morning I carefully reread every message.
>
>Several people commented that "XML Doesn't Care" and "XML is just syntax".
>I'd like to apply those comments to the notion of explicit relationships.
>
>In this message I would like to reverse my stand and argue that
>it is not possible for XML markup to state explicit relationships.
>I will argue that explicit relationships in markup is a myth.
>
>Consider this markup:
>
><Lot id="1">
> <Picker id="John">
> ...
> </Picker>
></Lot>
>
>What's the relationship between the Lot and the Picker?
>
>The tag names have meaning to us as humans. Thus, it is tempting for us to
>read the markup and infer a relationship that in fact does not exist.
>
>To an XML parser the markup looks like this:
>
><W#*jQ10x>
> <p99@% I8s="John">
> ...
> </p99@%>
></W#*jQ10x>
>
>That is, to an XML parser the tags are just a collection
>of meaningless characters.
>
>The advantage of us humans viewing the markup in this later form is that it
>lessens
>our overwhelming temptation to infer meaning. Oddly, the relationship
>becomes clearer! We now see that the relationship is simply:
>
> p99@% is nested within W#*jQ10x
>
>Or:
>
> Picker is nested within Lot
>
>No other statements can be made regarding the relationship
>between the Lot and the Picker.
>
>Thus, it is erroneous to state this relationship:
>
> The Picker is located on the Lot
>
>This "located on" relationship may not be stated. It is bringing
>in knowledge that is not present in the markup. (The knowledge
>is coming from the mind of the reader)
>
>In fact, even the "nested within" relationship is only known if
>the processing application happens to be an XML-aware application. A
>non-XML-aware
>application would not even be able to recognize the "nested within"
>relationship.
>
>I make these two assumptions for this discussion:
>
>1. The processing application is an XML-aware application.
>2. The processing application is completely ignorant of our vocabulary.
>
>Let us continue with our example.
>
>Suppose that we decide that the "nested within" relationship is not
>sufficiently
>precise for our desires. Can we design the markup to make the
>relationship more precise?
>
>How about this:
>
><Lot id="1">
> <locatedOn>
> <Picker id="John">
> ...
> </Picker>
> </locatedOn>
></Lot>
>
>It would appear that the <locatedOn> element is making explicit
>the relationship between the Lot and the Picker.
>
>It is best to resist the temptation of our mind to add knowledge to the
>markup.
>So, let us convert the example into something less interpretable by our mind
>(but
>equally interpretable to a machine):
>
><W#*jQ10x>
> <vb*@34>
> <p99@% I8s="John">
> ...
> </p99@%>
> </vb*@34>
></W#*jQ10x>
>
>This makes it clear that the only relationships which can be stated are:
>
> p99@% is nested within vb*@34, which is nested within W#*jQ10x
>
>or:
>
> Picker is nested within locatedOn, which is nested within Lot
>
>Introducing the locatedOn element has done nothing to make the relationship
>between the Lot and the Picker more explicit. It has only served to push
>the Picker
>to a deeper nesting level (and thus more digging is needed to get at it).
>
>Any relationship information beyond "nested within" must be introduced
>outside the markup, i.e.,
>by human-engineered applications that process the markup.
>
>Conclusions/Observations/Questions
>
>1. No matter how you design your XML it won't make any difference in
>semantics.
> Specifically, nested elements will always yield the "nested within"
>relationship
> and nothing else.
>
>2. There is no such thing as markup that enables you to specify an "explicit
>relationship"
> between components. Any relationship semantics beyond "nested within"
> is entirely a product of the application processing the markup.
>
>3. XML places the whole burden of semantics squarely upon the shoulders of
> processing applications. Consequently, the sender and receiver must
> necessarily be tightly coupled (i.e., have shared semantics).
>
>4. All message exchanges are nothing more than a series of encodings and
>decodings.
>
> For example, this message:
>
> "The Picker whose name is John, is currently located on Lot number 1"
>
> May be encoded like this:
>
> <Lot id="1">
> <Picker id="John">
> ...
> </Picker>
> </Lot>
>
> Or it may be encoded like this:
>
> <W#*jQ10x>
> <p99@% I8s="John">
> ...
> </p99@%>
> </W#*jQ10x>
>
> Either is a perfectly fine encoding. Communication occurs when the
>receiver
> possesses the proper decoder. Thus, a decoder must be able to decode the
>
> above code back into the original message:
>
> "The Picker whose name is John, is currently located on Lot number 1"
>
> If the receiver does not have the proper decoder then communication
>cannot occur.
>
>5. Is it conceivable that a code could be processed by many different
>decoders?
>
>6. Are there such things are "self-decoding codes"? (I guess that a virus
>is
> an example.)
>
>7. Is it reasonable that a generic message format (i.e., XML) should carry
>at least some of
> the burden of semantics? Should XML 2.0 possess more semantics than is
>currently found
> in XML 1.0?
>
>Comments? /Roger
>
>
>
>
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begin:vcard
fn:Rick Marshall
n:Marshall;Rick
email;internet:rjm@zenucom.com
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