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Subject: Re: [search-ws] FW: OASIS/SRU: Operation Parameter
I am not sure I understand the distinction between SRW and SRU. To me they are just SOAP and REST bindings to the same abstract interface. IMHO, We can build Search-WS with an ROA based abstract interface and map it to a REST interface and a SOAP interface. BTW it is much easier to map a ROA service to REST *and* SOAP than to map a AOA service to REST. Fortunately, I think Search-WS fits ROA better than AOA so we can have both a REST and SOAP interface. It would have been messier if AOA was a better fit for Search-WS. Ray Denenberg wrote: > > Farrukh -- thanks for posting this. But the question it raises for me is > how do we reconcile SRW with SRU, if SRU is best modeled as ROA and SRW > (based on SOAP) is best modelled as AOA? > > --Ray > > -----Original Message----- > From: SRU (Search and Retrieve Via URL) Implementors [mailto:ZNG@loc.gov] On > Behalf Of Farrukh Najmi > Sent: Sunday, November 25, 2007 3:05 PM > To: ZNG@sun8.LOC.GOV > Subject: Re: OASIS/SRU: Operation Parameter > > ( > Resending after fixing an important typo between ROA and AOA below Please > ignore previous version. > ) > > Rob Sanderson wrote: > >> On Wed, 2007-11-14 at 10:06 -0500, Ray Denenberg, Library of Congress >> wrote: >> >> >>> There is a proposal to eliminate the operation parameter, >>> incorporating it instead in the base url, in some fashion. The reason >>> for the proposal is that this parameter is not consistent with REST >>> > principles. > >>> >>> >> >> >> REST is not the be all and end all of web services. >> >> Practically speaking it makes it slightly harder to implement as a >> single cgi script becomes out of the question. I don't see any >> practical advantage. >> >> So, unless someone can explain why this is a good idea without saying >> "because REST says so"... >> >> -1 >> >> > > Like most things this is not a black and white issue and there are > trade-offs that need to be considered. Let me try and summarize briefly... > > Broadly speaking, there are two architectural approaches to design services: > > 1. Resource-Oriented services > 2. Activity-Oriented services > > In a Resource-oriented architecture (ROA) the resources or data objects > are the focus while the operations or activities you perform on the > resources remain fixed no matter what type of resource one is dealing > with. SQL is an example of a ROA where the fixed interface is define by > SELECT, INSERT, DELETE, UPDATE operations. Another example is REST where > the fixed operations are defined by the GET, POST, PUT, DELETE > operations of the HTTP protocol. > > In an Activity-oriented architectures (AOA), the focus is on the > operations or activities you perform rather than the resources that are > the target of the operations or activities. SOAP is an example of a AOA > (sometimes referred to as Service Oriented Architecture or SOA). > > The benefit of ROA is that the architecture is completely unaffected as > the information model / resources are expanded to meet new requirements. > No new operations are required when new resource types are added. No > interface changes are needed. No protocol extensions are needed. > > The benefit of a AOA is that it is better suited to modeling an activity > such as a banking transaction or medical activity such as a prescription > order. > > So which is better? It depends upon the requirements of the application. > > If the application is focused more on resources, resources are what keep > growing unbounded and resources are more relevant to clients, then ROA > is a better fit. Examples of ROA in practice are Amazon, del.icio.us, > Flickr, Safari etc. > > However, if the application is focused primarily on activities or > operations, activities grow more than resources and activities are more > significant than resources to the client, then AOA is a better fit. > > IMHO, Search-WS fits in the first category where the number of > operations are fairly fixed, number of resources are unbounded and it is > resources and not operations that are more significant to clients. Thus > an ROA is a better fit for Search-WS. > > In an ROA the center of the universe is the resource and not the > activity or operation. The basic tenet is that operations are fixes and > resources are unbounded. Modeling operations in such an architecture is > counter to ROA. > > This is the basic argument why modeling *any* operation in *any* form > (including but not limited to operation parameter) in search-ws protocol > is not desirable, and that whenever possible, we should model resources > or algorithms and not operations within the search-ws protocol. > > Of course, if one can make a convincing argument that Search-WS is an > activity-oriented service then the argument would be to model operations > in the protocol and not resources. Does anyone believe that Search-WS is > an is an activity-oriented service rather than a resource-oriented service? > > -- Regards, Farrukh Najmi Web: http://www.wellfleetsoftware.com
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