[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Are people really using Identity constraints specified in
Patrick, But that is the rub here, is it more complicated? Frankly schema works for tiny small schemas with few if any logical branches to the structure - but even there you run into difficulties - e.g. stock quote lookup, how tough is that? Put in stock ticker symbol - get back quote. Hmmm, but then the ticker is related to exchange, and status of the company, so could have prefix with colon separator, and so on - suddenly a tiny little something - and schema really cannot provide enough validation already. Unless you add more fields, and have prefix, exchange, ticker, name, but now you need rules - if I enter name and exchange, but not prefix and ticker.... how can I use schema to check the right permutations for me? But wait, I can declare varients of just the permutations of structure that I want and label them accordingly. Now I need a way for people to know what context to use what structure construct. Oh - how I do that? (hint - you need context variables). Then as soon as you get into significant information exchanges with dozens of inter-related fields - oh my! Schema really does have a very limited use profile. That is the way it was defined of course - they did start with a set of requirements. Trouble is few if any people who are using schema have bothered to read what the original design was intended to do. 9 times out of 10 it ain't what people are now trying to use schema for! No surprises then that it is sub-optimal for their needs. DW. Quoting Patrick Yee <kcyee@c...>: > On top of Schema checking, an even upper layer may offer checking of > semantics, too. This is, IMHO, a new concept which does not appear in > the TCP/IP stack. Needless to say, it is more complicated than Schema > checking. > Regards, -Patrick > > > Jimmy Zhang wrote: > > >IP packets are much simpler to check because the head > >fields are fixed in length. CRC checking is typical, > >and is equvalent to signature of SOAP. > > > >Other checking, such as IP, port, process id, TCP flow > >control etc, are less sophiscated than Schema. > > > >Deep content inspection offers to look at teh packet > >content,but still is less complicated than Schema. > > > >--- costello@m... wrote: > > > > > > > >>Hi Folks, > >> > >>I remember reading a long time ago a posting by > >>David Megginson. Paraphrasing, David said, "when > >>dealing with XML you are working down at the bare > >>metal". > >> > >>Other technologies work down at the bare metal, such > >>as TCP/IP. Perhaps there are lessons to be learned > >>there? Certain TCP/IP packets are rejected as bad > >>and the other packets are accepted and passed up to > >>other layers, where those layers perform additional > >>constraint checking. > >> > >>If we accept the conjecture that XML is down at the > >>bare metal level, then perhaps the only constraint > >>checking that should be done by an XML Schema is > >>parallel to the kinds of checking that is done on > >>TCP/IP packets. All other constraint checking is > >>passed up to other layers. > >> > >>Can someone characterize the kind of constraint > >>checking that is done on TCP/IP packets? What would > >>be the parallel constraint checking in XML Schemas? > >>/Roger > >> > >> > >> > >> > >> > >> > >> > >----------------------------------------------------------------- > > > > > >>The xml-dev list is sponsored by XML.org > >><http://www.xml.org>, an > >>initiative of OASIS <http://www.oasis-open.org> > >> > >>The list archives are at > >>http://lists.xml.org/archives/xml-dev/ > >> > >>To subscribe or unsubscribe from this list use the > >>subscription > >>manager: > >><http://www.oasis-open.org/mlmanage/index.php> > >> > >> > >> > >> > > > > > >----------------------------------------------------------------- > >The xml-dev list is sponsored by XML.org <http://www.xml.org>, an > >initiative of OASIS <http://www.oasis-open.org> > > > >The list archives are at http://lists.xml.org/archives/xml-dev/ > > > >To subscribe or unsubscribe from this list use the subscription > >manager: <http://www.oasis-open.org/mlmanage/index.php> > > > > > > > > > ----------------------------------------------------------------- > The xml-dev list is sponsored by XML.org <http://www.xml.org>, an > initiative of OASIS <http://www.oasis-open.org> > > The list archives are at http://lists.xml.org/archives/xml-dev/ > > To subscribe or unsubscribe from this list use the subscription > manager: <http://www.oasis-open.org/mlmanage/index.php> > >
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