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Business Ecology Initiative & Service-Oriented Solution

Michael Poulin

A Domain Service-Oriented Modelling or How SOA Meets DDD, Part 2

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As we concluded in previous post, Domain Service-Oriented Modelling or DOSOM© is a combination of Domain-Driven Design and Model-Driven Architecture (MDA) in the sphere of service orientation. Before discussing particular aspects of DOSOM©, we need to clarify its interposition with Reference Architecture (RA).

There are two categories: 1) RA as a set of definitions and guidelines for a particular domain; 2) RA as a template solution for the architecture for particular domain. In majority of cases, the template illustrates a solution for specific recurring problem that may or may not relate to the concrete task in the hands. This is why the RA umbrella frequently covers guidelines and template/example together.

For instance, The Healthcare Services Specification Project (HSSP) [1] represents its own standard - so-called "Healthcare-SOA Reference Architecture" (H-SOA-RA). The H-SOA-RA standardises the lexicon of the healthcare Software and the Software Definition Framework (SDF) - the detailed implementation guidance for the services [2]. Additionally, the H-SOA-RA includes a System of SOA Components (SoSC) - a reference to the service implementation that fits within the architecture. The H-SOA-RA engages MDA approach to specify an associated SDF [3].

The HSSP has all - a model driven design, mandatory semantics and ontologies for the Healthcare domain, and even a reusable example of business service implementation. However, individual companies are not obliged to adopt implementation templates like SoSC because the variety of specific domain problems within the companies may be not reflected in full in the 'standardised' reference implementation. Moreover, individual companies usually require faster reactions to the changes than any industry-centralised organisation can provide. As a result, the major value for individual companies is the regulated domain semantics/ontologies and guidelines (such as SDF); only inter-enterprise communication implementations (e.g. interfaces) could be standardised for the interoperability purposes.

At the same time, DOSOM© realises those semantics/ontologies and guidelines in the form of seamless stream of the Domain Models where each lower organisational level can inherit the model constraints from the higher levels but also can encapsulate more and more domain details. Also, at each level, if it is needed, the DOSOM© can be transformed into concrete platform-specific frameworks for different business cases. This is much more practical than the top-level case-natural implementation examples of Reference Architecture.

Figure 1 (Domain knowledge transition cycle) illustrates how domain knowledge may be passed from the industry into the enterprise and, then, through service-oriented modelling into DDD resulting in the Business Services and corporate Products for the consumers in the market. The RA contributes the domain guidelines into the modelling process and provides "how to do" examples in its template solutions. All steps of transferring domain knowledge into the Products rotate around standardized service orientation terms and definitions provided by the standard bodies like OMG or OASIS. The role of DOSOM© and DDD is in translation of the global standards into the domain specific constructs preserving the service-oriented principles.

(to be continued)

References:

1. HSSP 'Practical Guide' Project Dashboard
2. HSSP Wiki
3. Healthcare SOA Reference Architecture, "OMG SOA in Healthcare" Workshop


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In this blog, Michael Poulin writes about business and technology ideas, concepts, methodologies and solutions leading to service-oriented enterprise, the primary instrument for obtaining business objectives in fast-changing environments.

Michael Poulin

Michael Poulin is an enterprise-level solution architect working in the financial industry in the U.K. and the United States.

He specializes in building bridges between business needs and technology capabilities with emphasis on business and technical efficiency, scalability, robustness and manageability. He writes about service orientation, application security and use of modern technologies for solving business problems. He contributes to OASIS SOA standards as an independent member and is listed in the the international "Who's Who of Information Technology" for 2001. View more

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