RE: [xml-dev] A bunch of components, but no mandated organization - reasonable?

["Chiusano Joseph" <chiusano_joseph@bah.com>]

> -----Original Message-----
> From: Roger L. Costello [mailto:costello@mitre.org] 
> Sent: Friday, January 14, 2005 8:42 AM
> To: 'XML Developers List'
> Subject: RE: [xml-dev] A bunch of components, but no mandated 
> organization - reasonable?
> 
> Hi Folks,
> 
> Many thanks for the outstanding messages!
> 
> Yesterday Michael Kay made an insightful observation.  He 
> noted that there can be an effective exchange of information 
> when there exists a "protocol"
> between the exchanging parties: 
> 
> > Of course it's possible to set up a system in which anyone who 
> > receives a customer record is expected to interpret it as meaning 
> > "please update the information you hold on this customer". Equally, 
> > it's possible to set up a system in which anyone who receives a 
> > customer record is expected to interpret it as meaning 
> "please phone 
> > this customer and find out what he wants". Any bunch of 
> bits you send 
> > me is meaningful if we've agreed a protocol, and 
> meaningless otherwise.
> 
> Thus, if there exists a protocol between us then I can 
> dynamically assemble a bunch of components and send them to 
> you.  And you will be able to dynamically understand my assembly!
> 
> Let me give some concrete examples.
> 
> Example - Trash Collection

A perfect example of GIGO :)
 
> Every Wednesday morning I bring all my trash out to the front 
> of my house.
> During the day a trash collector comes along and picks up the 
> trash.  When I return home in the evening the trash is gone.  
> 
> Information (trash) was exchanged.  And it occurred without 
> a-priori knowledge by either party of the specific 
> transaction that would occur.  

Is that really true? The person(s) that collected it had knowledge of
what to recognize and pick up - that is, they did not pick up
(hopefully) a cat that walked by, or the grass at the front of the
house, or a tree (assuming they could). They recognized the perinent
components and how they related to what was around them. So I would say
that this is not fully supportive of the notion of non a-priori
knowledge.

Kind Regards,
Joseph Chiusano
Booz Allen Hamilton
Strategy and Technology Consultants to the World
> The exchange was possible because: 
> 
> (1) Each party understood the components (containers of trash), and
> 
> (2) There existed a protocol between the sender (me) and the 
> receiver (the trash collector).  
> 
> The protocol employed: "I give, you take".
> 
> Example - Browsers
> 
> I have created some HTML pages and placed them on my web 
> site.  When your browser visits my web site it will make 
> effective use of the stuff that I have put in my HTML pages.  
> 
> Again, information was exchanged.  And it without a-priori 
> knowledge by either party of the specific transaction that 
> would occur.  The exchange was possible because: 
> 
> (1) Each party understood the components (HTML documents), and
> 
> (2) There existed a protocol between the sender (my web 
> server) and the receiver (your browser).  
> 
> The protocol employed: "I give, you take".
> 
> I suspect that the "I give, you take" protocol is a common, 
> powerful protocol.  Can you think of other common, powerful protocols?
> 
> Summary: Transferring Information using a Shared Grammar 
> versus a Shared Protocol
> 
> Given a bunch of components, how can the information in those 
> components be effectively transferred between you and I?  We 
> seem to be narrowing in on two approaches:
> 
> 1. Shared Grammar: craft an XML Schema that completely lays 
> out the order and number of occurrences of each component.  
> That is, completely specify the grammar for the components.  
> The grammar (XML Schema) is then the contract between sender 
> and receiver.
> 
> 2. Shared Protocol: define an exchange protocol.  The form of 
> the assembly of components that are sent is unspecified and 
> irrelevant.
> 
> [Tangential comment: there is a philosopher, Karl Popper, who 
> wrote (paraphrasing), "The quickest way to move a science 
> forward is through the use of provocative conjectures".  In 
> the spirit of Karl Popper I thus make the following 
> provocative conjecture.] 
> 
> Conjecture: Information exchange using shared protocols is a 
> superior approach to information exchange using shared grammars.  
> 
> In other words, when you create an XML Schema simply declare 
> a bunch of independent components, but don't mandate any 
> particular ordering of them.
> 
> [Another tangential comment: Popper says that after making a 
> conjecture it is important to test the conjecture.  So, let's 
> test the conjecture.]
> 
> Test 1: Support for information exchange in a dynamically changing
> environment: the Shared Protocol approach is a "loosely 
> coupled" approach.
> That is, the nature of the "payload" is irrelevant (I use the 
> term "payload"
> here as it just dawned on me that HTTP is a "protocol" and 
> the information transferred using the HTTP protocol is called 
> a "payload").  
> 
> Conversely, the Shared Grammar approach is not well-suited to 
> dynamic environments.  Witness the great amount of effort and 
> coordination that is required to alter an XML Schema.
> 
> Test 2: ??? (What are some other tests that might be applied 
> to the two
> approaches?)
> 
> /Roger
> 
> 
> 
> 
> 
> 
> 
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