[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] | [List Home]
Subject: Re: [soa-rm] Opacity calumny
Good bokeh: http://www.flickr.com/photos/mattmackenzie/24169027/ I just wanted to use the word in soa-rm, because I really do think there is a such thing as "good" blur, even in technical specification. -matt Ken Laskey wrote: > Thanks, Joe. Obviously more than I ever wanted to know on the subject. > > But I wish you good bokeh :-) > > Ken > > At 10:59 AM 7/13/2005, Chiusano Joseph wrote: > >> > Sometimes we need to value bokeh, as oposed to sharp focus. >> >> For those who are curious: http://www.kenrockwell.com/tech/bokeh.htm >> (Bokeh Explained) >> >> Joe >> >> Joseph Chiusano >> Booz Allen Hamilton >> O: 703-902-6923 >> C: 202-251-0731 >> Visit us online@ http://www.boozallen.com >> >> >> > -----Original Message----- >> > From: Matthew MacKenzie [mailto:mattm@adobe.com] >> > Sent: Wednesday, July 13, 2005 10:37 AM >> > To: Ken Laskey >> > Cc: Chiusano Joseph; soa-rm@lists.oasis-open.org >> > Subject: Re: [soa-rm] Opacity calumny >> > >> > I personally view our various RM elements as "roles", so from >> > my perspective a piece of software may fill many roles. A >> > piece of software's ability to fill more than one role is >> > therefore not really interesting to us. >> > >> > Sometimes we need to value bokeh, as oposed to sharp focus. >> > >> > -matt >> > >> > Ken Laskey wrote: >> > >> > > It may act in both the client and the server capacities but >> > it doesn't >> > > have to. I know of an example where a DoD system had a >> > huge number of >> > > APIs (I seem to remember 1200) and they had a utility that >> > generated >> > > WSDLs for each one and said they've complied with making things >> > > visible and accessible because here were your Web services. >> > > >> > > Somehow that seems like complying with the letter of the >> > law without >> > > serving the spirit or furthering the intent. >> > > >> > > Ken >> > > >> > > At 09:49 AM 7/13/2005, Chiusano Joseph wrote: >> > > >> > >> > For example, if I take an existing client-server system and just >> > >> > advertise the interface to that server - does this give me SOA? >> > >> >> > >> IMHO, no. The reason is that with client-server, a client >> > is a client >> > >> and a server is a server. With SOA, a service may act in both >> > >> capacities (consumer and producer - or whatever terms you >> > would like to use). >> > >> >> > >> Joe >> > >> >> > >> Joseph Chiusano >> > >> Booz Allen Hamilton >> > >> O: 703-902-6923 >> > >> C: 202-251-0731 >> > >> Visit us online@ http://www.boozallen.com >> > >> >> > >> >> > >> > -----Original Message----- >> > >> > From: Bashioum,Christopher D [mailto:CBASHIOUM@mitre.org] >> > >> > Sent: Wednesday, July 13, 2005 9:47 AM >> > >> > To: Chiusano Joseph; soa-rm@lists.oasis-open.org >> > >> > Subject: RE: [soa-rm] Opacity calumny >> > >> > >> > >> > I agree with your assertion of a continuum that goes >> > from uncoupled >> > >> > to tightly coupled. However, I am not so sure that the >> > concept of >> > >> > loose coupling does not belong in the RM (but not convinced it >> > >> > does, either). >> > >> > >> > >> > >> > >> > For example, if I take an existing client-server system and just >> > >> > advertise the interface to that server - does this give me SOA? >> > >> > What if the client and the server are very tightly >> > coupled - where >> > >> > the client sometimes sends messages to the server and sometimes >> > >> > just directly accesses the data store that the server is using? >> > >> > What if the client and the server both share the data store, and >> > >> > only send messages to each other when the data store is updated? >> > >> > >> > >> > I am still struggling with this, as I am not sure how to >> > "measure" >> > >> > the degree of coupling, and even if I did know how to >> > measure it, I >> > >> > am not sure what the threshold would be for SOA. But, >> > just because >> > >> > it is hard, I would hate to not address it. I think >> > that the idea >> > >> > of loose coupling (however subjective that is) is >> > inherent to SOA. >> > >> > If you don't have it, you don't have SOA. >> > >> > >> > >> > Thoughts? >> > >> > >> > >> > -----Original Message----- >> > >> > From: Chiusano Joseph [mailto:chiusano_joseph@bah.com] >> > >> > Sent: Wednesday, July 13, 2005 9:32 AM >> > >> > To: soa-rm@lists.oasis-open.org >> > >> > Subject: RE: [soa-rm] Opacity calumny >> > >> > >> > >> > I believe that the degree of coupling is something outside the >> > >> > scope of an RM, as it is more of a concrete aspect. It does, >> > >> > however, belong in an RA and within concrete domain >> > architectures. >> > >> > >> > >> > Joe (not Duane hijacking Joe's e-mail account;) >> > >> > >> > >> > Kind Regards, >> > >> > Joseph Chiusano >> > >> > Booz Allen Hamilton >> > >> > O: 703-902-6923 >> > >> > C: 202-251-0731 >> > >> > Visit us online@ http://www.boozallen.com >> > >> > >> > >> > >> > >> > > -----Original Message----- >> > >> > > From: Bashioum,Christopher D [mailto:CBASHIOUM@mitre.org] >> > >> > > Sent: Wednesday, July 13, 2005 9:14 AM >> > >> > > To: Michael Stiefel; soa-rm@lists.oasis-open.org >> > >> > > Subject: RE: [soa-rm] Opacity calumny >> > >> > > >> > >> > > Agreed - so is there something about the loose coupling and >> > >> > the design >> > >> > > of the interfaces that is peculiarly SOA (and thus >> > would fit in >> > >> > > the RM), or is a tightly coupled interface still ok? I tend to >> > >> > think that >> > >> > > we need to capture something in the RM that focuses on >> > >> > loose coupling >> > >> > > - which is similar to the OO concept of public vs. private >> > >> > > (Frank's earlier assertions). >> > >> > > >> > >> > > -----Original Message----- >> > >> > > From: Michael Stiefel [mailto:development@reliablesoftware.com] >> > >> > > Sent: Wednesday, July 13, 2005 9:01 AM >> > >> > > To: Bashioum,Christopher D; soa-rm@lists.oasis-open.org >> > >> > > Subject: RE: [soa-rm] Opacity calumny >> > >> > > >> > >> > > I agree. >> > >> > > >> > >> > > Access through interface does not, however, >> > automatically get you >> > >> > > loose coupling. Poorly designed interfaces can produce >> > >> > tight coupling. >> > >> > > >> > >> > > Michael >> > >> > > >> > >> > > At 09:37 PM 7/12/2005, Bashioum,Christopher D wrote: >> > >> > > > Ken, et. Al., >> > >> > > > >> > >> > > >I was reading your email thread and started thinking about >> > >> > opacity as >> > >> > > it >> > >> > > >relates to the concept of loose coupling. It seems to me >> > >> > > that the real >> > >> > > >issue is loose coupling as opposed to opacity per se. >> > One could >> > >> > > publish >> > >> > > >all the specs related to a service, including the actual >> > >> > > code, as part >> > >> > > >of the service description. As long as access to the >> > >> > > internals of the >> > >> > > >service is strictly via the interface, then you still >> > have loose >> > >> > > >coupling (and, a service). If, on the other hand, you don't >> > >> > > >tell >> > >> > > anyone >> > >> > > >about the internals of a service, but you still allow >> > >> > access to the >> > >> > > >internals via globals or back-door methods, you will not >> > >> > have loose >> > >> > > >coupling. >> > >> > > > >> > >> > > >I think opacity is really a surrogate for loose coupling. >> > >> > In other >> > >> > > >words, its not about what you know of the service via its >> > >> > > metadata, its >> > >> > > >what you can access of the internals of the service (thus the >> > >> > > >private/public that Frank mentions). Ken - I think this is >> > >> > > also what >> > >> > > >you were trying to say also (thus, the ever more violent >> > >> > agreements >> > >> > > >below). So, that being said, we should probably address this >> > >> > > >more succinctly in the document. >> > >> > > > >> > >> > > >-----Original Message----- >> > >> > > >From: Ken Laskey [mailto:klaskey@mitre.org] >> > >> > > >Sent: Monday, July 11, 2005 5:24 PM >> > >> > > >To: Michael Stiefel; Frank McCabe >> > >> > > >Cc: soa-rm@lists.oasis-open.org >> > >> > > >Subject: Re: [soa-rm] Opacity calumny >> > >> > > > >> > >> > > >Agree, agree, agree. This list is getting much too tame. >> > >> > > > >> > >> > > >I would suggest that the concept of opacity is relevant to >> > >> > > the RM, and >> > >> > > >the fact that there are tradeoffs and examples of tradeoffs >> > >> > > is relevant >> > >> > > >to the RM. I also think relating this to a/c/p is relevant >> > >> > > to the RM. >> > >> > > >Being an engineer, it is difficult to list all the >> > >> > problems and not >> > >> > > >propose solutions, but alas that is not part of the RM. >> > >> > So what of >> > >> > > >this is appropriate for the RA? >> > >> > > > >> > >> > > >Ken >> > >> > > > >> > >> > > >At 05:09 PM 7/11/2005, Michael Stiefel wrote: >> > >> > > > >I agree as well. >> > >> > > > > >> > >> > > > >Opacity is a design tradeoff and hence a concrete, not >> > >> > > > >abstract >> > >> > > issue. >> > >> > > >All >> > >> > > > >other things being equal more opacity is better >> > than less, but >> > >> > > > >in >> > >> > > >reality >> > >> > > > >you are trading off opacity for other things such >> > as how much >> > >> > > metadata >> > >> > > >you >> > >> > > > >publish and how much dependency you generate as a result. >> > >> > > > > >> > >> > > > >Michael >> > >> > > > > >> > >> > > > >At 04:31 PM 7/11/2005, Ken Laskey wrote: >> > >> > > > >>Frank, >> > >> > > > >> >> > >> > > > >>To agree even more violently, this raises (and I allude >> > >> > > to a little >> > >> > > in >> > >> > > > >> > >> > > > >>the draft) the question of how to provide a means >> > to publish >> > >> > > metadata >> > >> > > >as >> > >> > > > >>it is found to be needed but in a way that supports a >> > >> > > consistent use >> > >> > > >of >> > >> > > > >>the metadata in evaluating an entity against >> > >> > unambiguously stated >> > >> > > >a/c/p, >> > >> > > > >>which themselves can be augmented and will evolve to >> > >> > meet business >> > >> > > >needs >> > >> > > > >>of the users (where if I am a design engineer, my >> > >> > business need is >> > >> > > to >> > >> > > > >>find the technically correct solution engine). >> > >> > > > >> >> > >> > > > >>This represents a much ignored need as well as a >> > >> > terrible run-on >> > >> > > > >>sentence. :-) >> > >> > > > >> >> > >> > > > >>Ken >> > >> > > > >> >> > >> > > > >>At 04:10 PM 7/11/2005, Frank McCabe wrote: >> > >> > > > >>>Ken: >> > >> > > > >>> >> > >> > > > >>> I think we are in violent agreement. The essence of >> > >> > the Java >> > >> > > > >>>execution engine example is that it is precisely that the >> > >> > > > >>>implementation is important -- not whether or not its >> > >> > > good style!! >> > >> > > > >>> >> > >> > > > >>> Incidentally, if it is important to know who wrote the >> > >> > > > >>>implementation, then that too should be part of the public >> > >> > > >description. >> > >> > > > >>> >> > >> > > > >>> Perhaps another aspect concerns the on-the-wire vs. >> > >> > > > >>> resource >> > >> > > model >> > >> > > > >>>of service semantics. In the resource pov, issues of >> > >> > > implementation >> > >> > > > >>>(transparent or otherwise) figure prominently. In the >> > >> > > on-the-wire >> > >> > > > >>>pov, you only look at the message traffic; and do not >> > >> > > even consider >> > >> > > > >>>the implementation. >> > >> > > > >>> >> > >> > > > >>> They are related of course: a message is valid if it is >> > >> > > > >>> well >> > >> > > formed >> > >> > > > >>>(in some communication language) and if the implied >> > >> > predicate is >> > >> > > > >>>satisfied (there really is money in your bank account). >> > >> > > > >>> >> > >> > > > >>> But, a Service Oriented Semantics (SOS) would >> > focus on the >> > >> > > on-the- >> > >> > > > >>> wire interpretation and require that the service >> > >> > > > >>>participants faithfully reflect the messages in their >> > >> > > > >>>systems. I.e., it is >> > >> > > similar >> > >> > > > >>>to the model/proof theory distinction: provided that >> > >> > the service >> > >> > > > >>>implementation is a correct Interpretation of the >> > >> > communication, >> > >> > > the >> > >> > > > >>>participants can focus on the Formulae being communicated. >> > >> > > > >>> >> > >> > > > >>>That all being said, there are definite limits to >> > descriptions. >> > >> > > I.e., >> > >> > > > >>>there will always be unstated (unstateable?) assumptions >> > >> > > that are >> > >> > > > >>>required to be shared for successful interactions. >> > >> > > > >>> >> > >> > > > >>>Frank >> > >> > > > >>> >> > >> > > > >>>On Jul 11, 2005, at 12:49 PM, Ken Laskey wrote: >> > >> > > > >>> >> > >> > > > >>>>Frank, >> > >> > > > >>>> >> > >> > > > >>>>Opacity/transparency is not a dimension on which to >> > >> > distinguish >> > >> > > > >>>>services; it is more of a fallacy that we may need to >> > >> > > explain our >> > >> > > > >>>>way around. This ties in very much with what I've >> > >> > tried to say >> > >> > > > >>>>about metadata and how metadata characterizing >> > an instance >> > >> > > > >>>>is >> > >> > > often >> > >> > > > >>>>the basis upon which the instance is evaluated in the >> > >> > > context of >> > >> > > > >>>>assumptions, constraints, and policies (a/c/p) of >> > >> > providers and >> > >> > > > >>>>consumers. In some circumstances, the amount of >> > >> > > information that >> > >> > > > >>>>needs to be published about an entity may maintain >> > >> > > little in the >> > >> > > > >>>>way of its opacity, but that is more likely related to >> > >> > > a/c/p than >> > >> > > > >>>>it is to WSDL. >> > >> > > > >>>> >> > >> > > > >>>>See more inline. >> > >> > > > >>>> >> > >> > > > >>>>At 03:23 PM 7/11/2005, Frank McCabe wrote: >> > >> > > > >>>> >> > >> > > > >>>>>I read the revised section on services. And an issue >> > >> > > that made me >> > >> > > > >>>>>uneasy before has resurfaced -- about opacity. >> > >> > > > >>>>> >> > >> > > > >>>>>I think that the opacity/transparency dimension >> > is not a >> > >> > > > >>>>>good >> > >> > > basis >> > >> > > > >>>>>for distinguishing services. I am aware of the >> > >> > intuition: that >> > >> > > > >>>>>somehow when you use a service you should not have to >> > >> > > worry about >> > >> > > >the >> > >> > > > >>>>>implementation. But what does it mean to say: "the >> > >> > > implementation >> > >> > > >is >> > >> > > > >>>>>hidden from the service consumer"? If the service is >> > >> > > to add lists >> > >> > > >of >> > >> > > > >>>>>numbers then its implementation is hidden provided >> > >> > numbers are >> > >> > > >added >> > >> > > > >>>>>up correctly. (I.e., we should not care about whether >> > >> > > its in C++ >> > >> > > or >> > >> > > > >>>>>C#; multi-threaded or federated). >> > >> > > > >>>> >> > >> > > > >>>>So here the service adds numbers and while we can >> > >> > > imagine what is >> > >> > > > >>>>happening, we care no more of the specific than >> > we do when >> > >> > > > >>>>we >> > >> > > punch >> > >> > > > >>>>numbers into a calculator. >> > >> > > > >>>> >> > >> > > > >>>> >> > >> > > > >>>>>But, some services are explicitly about >> > >> > implementation issues: >> > >> > > > >>>>>security services, workload distribution services, >> > >> > java remote >> > >> > > > >>>>>execution engine services etc. etc. I.e., it is of >> > >> > the essence >> > >> > > that >> > >> > > > >>>>>to use a Java remote execution service, you >> > have to send >> > >> > > > >>>>>it a >> > >> > > java >> > >> > > > >>>>>class to execute. In that sense, the implementation is >> > >> > > critical. >> > >> > > > >>>> >> > >> > > > >>>>But you call a java remote execution engine when >> > you have >> > >> > > > >>>>an appropriate java class to execute. If it is >> > a general >> > >> > > > >>>>service >> > >> > > that >> > >> > > > >>>>is implemented as a java remote execution then the WS >> > >> > interface >> > >> > > > >>>>should more likely be a collector of information that >> > >> > > (inside the >> > >> > > > >>>>service) is rewritten as the necessary java class. You >> > >> > > > >>>>could require a java class as input but I'm not >> > sure that >> > >> > > > >>>>would be considered "good style". >> > >> > > > >>>> >> > >> > > > >>>> >> > >> > > > >>>>>A clearer distinction is public/private. A service is >> > >> > > characterized >> > >> > > > >>>>>by a public description of its functionality. The public >> > >> > > >description >> > >> > > > >>>>>should be sufficient to be able to successfully >> > >> > > interact with the >> > >> > > > >>>>>service; and no additional information should >> > be required. >> > >> > > > >>>> >> > >> > > > >>>>Not really because what you consider part of the private >> > >> > > > >>>>information I might consider very pertinent to >> > >> > deciding whether >> > >> > > > >>>>your service is suitable for my purposes, i.e. I need >> > >> > it to be >> > >> > > > >>>>public. For an extreme example, I used to work for >> > >> > > your company >> > >> > > > >>>>and I know one of your developers is clearly >> > >> > > incompetent and I'd >> > >> > > > >>>>never use anything that idiot touched. >> > >> > > > >>>> >> > >> > > > >>>>The challenge is in defining "should be sufficient to >> > >> > > be able to >> > >> > > > >>>>successfully interact with the service". I >> > think we need >> > >> > > > >>>>to discuss opacity in these terms because it is strongly >> > >> > connected >> > >> > > > >>>>with SOA and may be more useful as a vague >> > concept than as >> > >> > > > >>>>an absolute measure. >> > >> > > > >>>> >> > >> > > > >>>> >> > >> > > > >>>>>Frank >> > >> > > > >>>> >> > >> > > > >>>>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 >> > >> > > >/ >> > >> > > > >> > >> > > >>------------------------------------------------------------ >> > >> > > ---------- >> > >> > > >------------ >> > >> > > > >> >> > >> > > > >> >> > >> > > > > >> > >> > > > > >> > >> > > > >> > >> > > >-- >> > >> > > > >> > >> > > >------------------------------------------------------------- >> > >> > > ---------- >> > >> > > - >> > >> > > >--------- >> > >> > > > / 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 >> > / >> > > >> > > >> > ---------------------------------------------------------------------- >> > > ------------ >> > > >> > > >> > > >> > >> > > > > -- > > --------------------------------------------------------------------------------- > > / Ken > Laskey \ > | MITRE Corporation, M/S H305 phone: 703-983-7934 | > | 7515 Colshire Drive fax: 703-983-1379 | > \ McLean VA 22102-7508 / > > ---------------------------------------------------------------------------------- > > >
[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] | [List Home]