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