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more MOPs

• To: "Jeff Lowery" <Jeff.Lowery@c...>, <xml-dev@l...>
• Subject: more MOPs
• From: "Owen Walcher" <news@o...>
• Date: Wed, 12 Feb 2003 11:48:03 -0700
• Importance: Normal
• In-reply-to: <4827EC373E03DB44AC2AB3900430896B0265CA@w...>

>> data + context = information

>data - context = a bunch of random bits

No, I think:

data - context = RDBMS

where the meta data and the data are separated (and the meta data is static)

>So your assertion doesn't seem all that profound. Can data even exist
>without context? I don't think it's data if there's no context to which it
>can be applied.  Does an XML document, as a store of data, have a special
>ability to carry context?  I don't see how it does.


Is there not obvious context between the <name> elements in the following
XML?

<Invoice>
	<BillingAddress>
		<Contact>
			<name>Bill Payor</name>
		</Contact>
	</BillingAddress>
	<ShipToAddess>
		<Receiver>
			<name>Joe Receiver</name>
		</Receiver>
	</ShipToAddress>
	<PurchasedBy>
		<name>John Purchaser</name>
	</PurchasedBy>
<Invoice>

We have:
Invoice>BillingAddress>Contact>name = Bill Payor
Invoice>ShipToAddress>Receiver>name = Joe Receiver
Invoice>PurchasedBy>name = John Purchaser

Each name has it's context directly associated with it based on the
hierarchy of the XML.

If I gave you the data: Diana, you would not know what it means, and
therefore could not interpret how to process it, but if I gave you:

Owen>Wife>name = Diana then you have the context you need to process the
data, because it is now *information*


>> Adaptive application can be written (if certain XML modeling rules are
>> followed), that allow Meta Object Protocols (MOP) and
>> Reflection to be used
>> to dynamically extend the runtime environment.

>Ah-yup.  But a specific application of XML technology does not by itself
>constitute an proof that there is an underlying data model for the syntax
>that is XML.  The fact that you can construct a data model (or information
>model, if you like) using XML syntax does argue for its flexibility in
being
>adaptable to a wide variety of programming a modeling domains.  But it is,
>by the same token, adaptable to wide variety of document domains,  and
>serialized representations of all sorts of things.

Do not confuse data model (logical) with data base (physical), which I think
may be the disconnect.  So many people use XML for transfer, and then shred
or CLOB it into their existing *data* bases, without regard to the fact that
the XML *could* be formatted in such as way (logical=physical) as to require
minimal translation, if the format was more information rich, and less
transfer brief.

>It think using XML for MOP-ish descriptions is an excellent idea myself,
and
>have suggested as much this list in the recent past for describing how to
>represent XML data in objects and collections of objects.  It doesn't mean
>that XML has a fixed underlying data model, though. You can make it
>represent such data models, but that's different hill of beans.

No, XML has no *fixed* data model, rather it can be structured to represent
any specific Information Model you like. (logical=physical, and both data
and meta data dynamic)

I guess I will go on to say that Objects (and object technology in general)
has hit a wall, or has failed us.  I say this because we are still trying to
define things (like processable code) a-priori, without regard to the
behaviour that someone later might wish.  An example of recent point: look
at the discussion of HTTP protocol, where we endlessly debate whether it
should be used for things it wasn't designed to do.  If all people use XML
for is to serialize their objects, then they have missed the point of XML as
a synergistic effect upon which the way applications in the future will be
built.  Object behaviour (e.g. methods) *must* be as flexible as the data
(instances variables).

Owen

• References:
  • RE: web services stack
    • From: Jeff Lowery <Jeff.Lowery@c...>

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