Re: [soa-rm] another possible SOA diagram (revised)

[Ken Laskey <klaskey@mitre.org>]

So am I correct in the following example:

concept - something that can take a set of numbers and return me the sum

identifier - www.addnumbers.org

representation -
   sum = 0
   until list is empty
     get next
     add next to sum
     repeat until
   send back result

Ken

At 04:26 PM 5/24/2005, Francis McCabe wrote:
>We developed a resource model as part of the W3C WSA. That, in turn
>was based on the REST architecture (abstracted a bit) by Roy Fielding.
>
>However, at its heart, the resource model is both simple and subtle:
>it is trying to nail down something that has been the source of a lot
>of confusion (and superstition): the relationship between the names
>of things and the things themselves.
>
>There are three concepts that, together, form the resource
>conception: the concept of a resource, the concept of an identifier
>(a.k.a. symbol, URL, bag'o'bits, etc.) and the concept of a
>representation (a.k.a. image, sensation etc.).
>
>Once nailed down, you can then attach other properties to particular
>kinds of resources: at one end you have ownership and at the other
>end you have boulders, Web Services, and pictures of Roy Fielding's
>car. (Sorry, in-joke).
>
>Frank
>
>On May 24, 2005, at 11:59 AM, Greg Kohring wrote:
>
>>Fank,
>>
>>I like the idea of importing an RM for "resource". Can you recommend
>>one we can use?
>>
>>Greg
>>
>>
>>Francis McCabe wrote:
>>
>>>Aaarrrgh ....
>>>   This was a big debate in the Web Services Description WG (WSDL
>>>2.0). About there being a resource behind the service.
>>>   This is the entirely spurious but very seductive idea of the
>>>one  true resource™.
>>>   For *some* people, it is right and appropriate for their
>>>application to think of the one true resource represented by
>>>their  service. But it is certainly not the general case; many
>>>services have  the character of filters (e.g., unit conversion
>>>services, ATM  machines, encryption services) which are not
>>>primarily concerned with  their own resources. Other services are
>>>all about *combining*  resources e.g., selling and delivering
>>>books, subscription and  notification services.
>>>   From other perspectives (e.g., service management, policy
>>>enforcement, deployment, etc. etc.), the service itself *is* a
>>>resource that has an existence independent of other resources it
>>>manipulates. For example, resources are *things* that can be
>>>bought;  and a service certainly meets that criteria.
>>>  Personally, I believe that all of this stuff on resources does
>>>not  belong in a SOA RM; the reason: resources have their own
>>>modeling and  we can simply layer on top of the concept.
>>>Frank
>>>On May 23, 2005, at 3:28 PM, Ken Laskey wrote:
>>>
>>>>Greg - see below
>>>>
>>>>At 02:33 PM 5/23/2005, Greg Kohring wrote:
>>>>
>>>>
>>>>>Sorry, but this diagram has a few problems.
>>>>>
>>>>>1) A "Service Interface" is a concrete representation of some of
>>>>>the
>>>>>constraints detailed in the contract; i.e., it is too concrete for
>>>>>being mentioned so prominently in a reference model.
>>>>>
>>>>
>>>>The service interface is more a representation of the data model
>>>>than a constraint, and I am referring to an unambiguous
>>>>prescription of the interface and not the implementing code.  A
>>>>such, I'd see it no more concrete than the specification of a
>>>>policy.
>>>>
>>>>
>>>>
>>>>
>>>>>2) It is the service that is the resource, not the service
>>>>>description.
>>>>>
>>>>
>>>>It has been a while since I read WSA, so my apologies if my use
>>>>of  the terms is different.  I see the resource as being
>>>>something that  provides something I need, whether data or
>>>>processing.  I see the  service as a means to gain access to the
>>>>resource but the resource  exists independent of the service.
>>>>Many services may access the  same resource, e.g. for different
>>>>guaranteed quality of service.
>>>>
>>>>
>>>>
>>>>>While it is certainly true that every service is a resource, the
>>>>>converse is not true.
>>>>>
>>>>
>>>>Again, this may go against past WSA work but I do not consider a
>>>>service to be a resource.  It is one means of accessing a resource.
>>>>
>>>>
>>>>
>>>>>You might even define an SOA is an architecture
>>>>>in which all resources are either themselves services or can
>>>>>only be
>>>>>accessed through services (i.e., they are part of the service's
>>>>>data
>>>>>model). Therefore, if your architecture only consists
>>>>>of services, you need not mention resources explicitly.
>>>>>
>>>>>-- Greg
>>>>>
>>>>>
>>>>>Ken Laskey wrote:
>>>>>
>>>>>
>>>>>>The resource is the implementation that in many cases was
>>>>>>created  to satisfy needs outside the SOA and only becomes part
>>>>>>of a SOA  in the same way that any software package becomes
>>>>>>part of your  computer.  Opacity says you know there is a
>>>>>>resource but the only  thing you know about it is what is
>>>>>>exposed through the service  description.
>>>>>>Attached is a very quick attempt to include in Duane's last
>>>>>>diagram.
>>>>>>Ken
>>>>>>
>>>>>>On May 23, 2005, at 9:18 AM, Christopher Bashioum wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>>>  OK - that makes sense.  In fact, I remember a book on SOA
>>>>>>>patterns  that
>>>>>>>talks about this (forgot the title, but the author is Paul
>>>>>>>Monday).
>>>>>>>In his
>>>>>>>view, what you are referring to as a service he would refer
>>>>>>>to  as an
>>>>>>>architecture adapter.  I.e., the implementation (resource) is
>>>>>>>done in a
>>>>>>>particular architural style.  In order to adapt that
>>>>>>>implementation to  the
>>>>>>>SOA architectural style one would us an architecture
>>>>>>>adapter.   (at  least
>>>>>>>that's what I got from his book - I may have misunderstood).
>>>>>>>
>>>>>>>So ... A second question for you -  do you think we need to add a
>>>>>>>resource
>>>>>>>box to the diagram that Duane sent out?  If so, what would be the
>>>>>>>relationship between the resource and the service?
>>>>>>>
>>>>>>>-----Original Message-----
>>>>>>>From: Ken Laskey [mailto:klaskey@mitre.org]
>>>>>>>Sent: Monday, May 23, 2005 9:11 AM
>>>>>>>To: Christopher Bashioum
>>>>>>>Cc: 'SOA-RM'
>>>>>>>Subject: Re: [soa-rm] another possible SOA diagram (revised)
>>>>>>>
>>>>>>>The resource is the real thing out there that provides a
>>>>>>>capability --
>>>>>>>in the 07 draft, there is a discussion of data resources vs.
>>>>>>>processing
>>>>>>>resources.  In general, a resource does not have to be
>>>>>>>service- enabled.
>>>>>>>   However for SOA, the resource must have (we can continue to
>>>>>>>debate
>>>>>>>this) a service interface that is one of the things published
>>>>>>>through
>>>>>>>the service description, and that service interface is how
>>>>>>>you  connect
>>>>>>>the resource to the underlying service infrastructure.
>>>>>>>Additionally,
>>>>>>>the service infrastructure has to provide certain TBD
>>>>>>>capabilities and
>>>>>>>likely overlaps but is not necessarily the same as what is
>>>>>>>often  termed
>>>>>>>an ESB bus.
>>>>>>>
>>>>>>>Ken
>>>>>>>
>>>>>>>On May 23, 2005, at 8:53 AM, Christopher Bashioum wrote:
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>>Ken,
>>>>>>>>
>>>>>>>>Intuitively, I like this one.  One question: how is the resource
>>>>>>>>different
>>>>>>>>than the service?  Also, for the TC to use, we may be able
>>>>>>>>to  identify
>>>>>>>>the
>>>>>>>>essential elements with a * and then the other optional
>>>>>>>>elements to
>>>>>>>>show
>>>>>>>>where they fit (for example, I see basic logging as non-
>>>>>>>>essential, but
>>>>>>>>this
>>>>>>>>diagram shows where it fits).
>>>>>>>>
>>>>>>>>The diagram may not show up in the actual RM doc, but it may
>>>>>>>>be  useful
>>>>>>>>for
>>>>>>>>us as a conceptual model.
>>>>>>>>
>>>>>>>>-----Original Message-----
>>>>>>>>From: Ken Laskey [mailto:klaskey@mitre.org]
>>>>>>>>Sent: Monday, May 23, 2005 12:43 AM
>>>>>>>>To: 'SOA-RM'
>>>>>>>>Subject: [soa-rm] another possible SOA diagram (revised)
>>>>>>>>
>>>>>>>>I played with the ideas in the sketch a bit more.  As noted
>>>>>>>>in the
>>>>>>>>previous email:
>>>>>>>>
>>>>>>>>I would not necessarily advocate it being used instead of
>>>>>>>>the  one  Duane
>>>>>>>>drew but given I had it, I thought I'd pass it around for
>>>>>>>>comments.
>>>>>>>>The 3D presentation may make it look too concrete but I was
>>>>>>>>looking  for
>>>>>>>>a way to show there was something SOA I was building
>>>>>>>>services  on and
>>>>>>>>there could be any number of services.  Note a resource could
>>>>>>>>be a
>>>>>>>>registry but even that would be exposed through services and
>>>>>>>>have
>>>>>>>>metadata.
>>>>>>>>
>>>>>>>>Ken
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>----------------------------------------------------------------- -- 
>>>>>>>---- -
>>>>>>>------------------
>>>>>>>Ken Laskey
>>>>>>>MITRE Corporation, M/S H305     phone:  703-983-7934
>>>>>>>7515 Colshire Drive                        fax:
>>>>>>>703-983-1379
>>>>>>>McLean VA 22102-7508
>>>>>>>
>>>>>
>>
>>
>

--
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   /   Ken 
Laskey                                                                \
  |    MITRE Corporation, M/S H305    phone:  703-983-7934   |
  |    7515 Colshire Drive                    fax:      703-983-1379   |
   \   McLean VA 22102-7508                                              /
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