SOA Standards

From Geostandards

W3C and OASIS standards

SOA - as an architectural concept - is separate from a specific technology. However, in the current state of technology, SOA can be closely associated with the Web Services standards family, also indicated as WS-*. The Web Services standard specifications are developed by a number of larger software providers (IBM, Microsoft, SAP and others) and presented to a standardisation institution for ratification. In practise, of all the Web Services standards, the standardisation organisations W3C and OASIS have the most important roles. See the overview below for the most important specifications released by both institutions.


Presenting a Web Service standard to one of those institutions and having it accepted does not, of course, guarantee that the standard is or will become an accepted market standard. Even though the Web Services standards are designed to be a cohesive technical whole, this does not mean they are also, per se, interoperable with each other. The Web Services Interoperability Organization (WS-I) plays an important role here. The WS-I releases so-called profiles on existing Web Services or on a combination of Web Services. In the same way as in the ISO tradition of the concept profile, these profiles are further constraints of the specification. For the implementation and possible purchase of tools, the WS-I profiles play an important role in the current stage of technology.

Different parties use the SOA concepts and services in different ways. A reader who is not aware of this could be confused.

First of all, SOA can be used in a general sense or in a specific technical manner. In the Nederlandse Overheid Referentie Architectuur (NORA), SOA is used in a general sense referring to the way in which both working processes and technical processes are applied in an organisation. The standpoint of OASIS, as described in the document 'Reference Model for Service Oriented Architecture' can be considered as a counterpart regarding SOA as a primarily technical matter. There is no right or wrong with this point of view, it mostly just reveals what sort of background the relevant organisation has. Of course, it is important to check whether the SOA has to be interpreted narrowly (only technically) or widely, in discussions about SOA.

The notion 'web services' is a technical one, but here is a formal owner as well and everyone is free to release a specification with 'web service' in the title. The highest authorisation with regard to the content of the web services is the W3C in the document 'Web Services Architecture'. The W3C releases Web Services specifications, but OASIS is active in this field too. Because the various web service specifications of W3C, OASIS and others were not always connected, it was necessary to set up a Web Service Interoperability Organization (WS-I).

It is confusing that the OGC Web Services which we know are not the web services for the geographical world, in the sense of the W3C definition. To date, the first results caused by the active efforts of OGC, are booked, mainly with the OWS-testbeds and the forthcoming OWS common.

Positioning the W3C, OASIS and OGC standards

The technical services are positioned in the figure below. The user patterns are defined, based upon the interaction pattern. Request-response applies to Business -to-Consumer (B2C), in general via web browsers and Business-to-Business (B2B). Usually for this application-application request it is important for a request to directly yield an answer. The applicant takes the initiative.

For publish-subscribe the initiative for the application-application traffic of messages is taken by the responder. This person places a message which is taken immediately or at a later point. The request is predictable and, in general, it is computed as a message would be.

 

The W3C, OASIS and OGC standards can be positioned with the figure above. This is done in the figure below.

The OGC standards focus mainly on request-response in which the user is most important and the application-orientation increases. Think of standards such as WMS, WFS and WCS. On the contrary, the ebXML is completely focused on the traffic of messages. With the WUS standards both worlds in the end can <missing part>. Ultimately, the application of a particular standard or a combination of them will be specified by the requirements of the application domain.

The question is whether OGC, OASIS and W3C will use each others standards and, if so, what standards will these be? The relationship that OGC has with W3C and OASIS is, for example, important in this context.

A Dutch example; in 2009 the choice was made to use the geo-standards of for .org/ OGC and ISO/TC 211 for request-response and for the traffic of messages to use the standards that the electronic government uses, (WUS and ebXML). Application diagrams are included in the content of the messages. They are expressed in GML when geo-information is applied. This creates a good combination of both worlds for the Netherlands, causing less discussion about technique but more about semantics.

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