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Re: Are people really using Identity constraints specifiedin X

• To: xml-dev@l...
• Subject: Re: Are people really using Identity constraints specifiedin XML schema?
• From: Patrick Yee <kcyee@c...>
• Date: Thu, 19 Aug 2004 12:21:31 +0800
• In-reply-to: <20040819024441.65568.qmail@w...>
• Organization: CECID
• References: <20040819024441.65568.qmail@w...>
• User-agent: Mozilla Thunderbird 0.7.2 (Windows/20040707)

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
>>
>>
>>
>>
>>
>>    
>>
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