SOA Reference Model

Generic Presentation

DRAFT: Not approved by the OASIS SOA RM TC.

Agenda

• What is SOA; what is a reference model for SOA• Why is a reference model needed• The OASIS SOA RM TC

In order define SOA…

• If SOA is Architecture, as the name implies, it should be definable as architecture.

• We should not do it by referencing an implementation.

• DEFINITION (from Charter): – “Architecture: A software architecture for a system is

the structure or structures of the system, which consist of elements and their externally visible properties, and the relationships among them.”

Closer look: “Service Oriented”

• Is a paradigm (model) for developing architecture.– Focus herein is “software & systems architecture”

• “Services” are the central concept, yet other concepts are present in all implementations.

• Is not currently defined other than a “common law” or “defacto” perception of what it is.

• Perceptions of what SOA is vastly disparate.

SOA Reference Model...

• Is not architecture for a single implementation.• Is a model for developing a range of Service Oriented

Architectures and analysis/comparison thereof.• Is a framework for understanding significant relationships

among the entities in a SOA environment.– DISCUSSION POINT: should the word “elements” be used in

place of “entities” above?

• Is based on a small number of unifying concepts of all SOA’s.

• A Reference Model is the best mechanism to define SOA.

To develop a Reference Model for SOA

• Ask questions:– What elements are common in all implementations of

SOA? ( be careful – think about this )– What abstract concepts do those elements represent?– What relationships exist amongst those concepts?– How do we represent those concepts without

referencing concrete implementations.– How does this relate to infrastructure concepts?

Draft: Candidate SOA Reference Model

DISCUSSION POINT: Details of how to interpret “Concept Maps” are included in the position paper submitted by Mackenzie, Nickull.

Base Components and Concepts of SOA

• Service: A service is a contractually defined behavior that can be implemented and provided by a component for use by any component solely based on the contract.

• Service Description: Technical parameters, constraints, policies that come together to define terms of invocation.

– DISCUSSION POINT: Is the contract part of the service description or referenced from it (if explicit)? The contract is shown linked to the service since it may be implied only and not physically able to be linked via a Service Description..

• Advertising: Makes all potential or intended consumers of a service on a fabric aware that the service exists. This MAY involve advertising the Service Description.

Base Components and Concepts of SOA

• Data Model: The specification and constraints imposed on instance data.

– QUESTION: Are semantics part of the data model? If not, how to others know what data model authors really mean?

• Contract: The implicit or explicit bi-lateral or multi-lateral agreement between the owners or agents of a service and those who use the service.

– QUESTION: Is “no contract” still ipso facto a contract? Is “zero” a number or “null” a value?

Agenda

• What is SOA; what is a reference model for SOA• Why is a reference model needed• The OASIS SOA RM TC

Existing situation

WSDL XML &SchemaSOAP

Base Standards

WS-RMWS

Addressing Reg/RepUDDI

WS-SecurityWS-Trust

WS-*

RequirementsQuestion: How do I map my Requirements to concrete architecture?

Developing SO Architecture

• Probably not logical to try and develop a “one size, fits all” architecture for SOA or WS.

• Not rational to develop multiple architectures in standards bodies for every set of requirements.

• Best solution: develop an SOA reference Model.– Used by architects to guide service oriented

architecture development.– Model for a way of thinking when developing

solutions.– Re-useable by multiple architects writing SOA for

multiple domains.– Helps architects slot existing standards into their

architectures.

SOA RM used for range of architectures

WSDL XML &SchemaSOAP

Base Standards

WS-RMWS

Addressing Reg/RepUDDI

WS-SecurityWS-Trust

WS-*

Requirements

Guides developments of

SOA-RM

SpecificArchitectures

Uses

Input for

QUESTION: Does this adequately explain the need for a reference model? Does this also clarify why a reference model is better than developing multiple Architectures?

Agenda

• What is SOA; what is a reference model for SOA• Why is a reference model needed• The OASIS SOA RM TC

OASIS SOA Reference Model TC

• Chartered February 2005• Problem to be solved:

– "Service Oriented Architecture" (SOA) as a term is being used in an increasing number of contexts and specific technology implementations, sometimes with differing or conflicting understandings of implicit terminology and components.

– The proposal to establish a Reference Model is intended to encourage the continued growth of specific and different SOA implementations whilst preserving a common layer that can be shared and understood between those or future implementations.

OASIS SOA Reference Model TC

• Purpose: – The SOA-RM TC will deliver a Service Oriented

Architecture Reference Model (SOA-RM). – The TC may also create sub-committees, promotional

material, liaisons or other promulgation of the TC's work, in order to promote the use of the SOA Reference Model.

– May help vertical industries develop SOA for their requirements.

Charter Definition

• Reference Model: A reference model is an abstract framework for understanding significant relationships among the entities of some environment, and for the development of consistent standards or specifications supporting that environment. A reference model is based on a small number of unifying concepts. A reference model is not directly tied to any standards, technologies or other concrete implementation details, but it does seek to provide a common semantics that can be used unambiguously across and between different implementations.

References

• OASIS SOA RM TC - http://www.oasis-open.org/committees/tc_home.php?wg_abbrev=soa-rm