>> 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
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