An Introduction to the OASIS Reference Model for Service Oriented Architecture (SOA)

2005 Adobe Systems Incorporated. All Rights Reserved.1

An Introduction to the OASIS Reference Model for Service Oriented Architecture (SOA)Duane Nickull

Senior Technical Evangelist

Adobe Systems, Inc.

22005 Adobe Systems Incorporated. All Rights Reserved.

Before we talk about SOA and where we want to go…

Would be nice if we had consensus on what SOA is! SOA is an architectural paradigm (model). So how do we express it as

architecture?

Is it sufficiently different from other types of architecture? If SOA is “X”, what is not SOA?

SOA does not specifically mean Web Services although WS is a popular implementation of SOA.


Defining SOA…

Should not do it by referencing an implementation.

If SOA is Architecture, it should be definable using a normative ADL.

A Reference Model is a good mechanism to define SOA. Why? (next slide).


The Reference Model for SOA…

Is not intended to be architecture for a single SOA system.

Is an ABSTRACT model for a range of Service Oriented architectures and analysis / comparison thereof.

Is a framework for understanding significant relationships among the entities in a SOA environment.

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


How does a RM relate to other stuff?


So what is SOA exactly?

A paradigm for organizing and using distributed capabilities that may be under the control of different ownership domains.

A framework for matching needs and capabilities.

A view of architecture focusing on “Services” as a mechanism to allows interactions between those with needs and capabilities.


Core Model for SOA

Dynamic perspective: 3 base concepts for interacting with services: • the visibility between service and consumers; • the interaction between them, and • real world effect of interacting with a service.


Additional Service concepts


Core Concepts for SOA - expanded


Core Concepts of SOA (Definitions)

Service: A mechanism by which needs and capabilities are brought together.

Service Description: Artifact declaring all relevant aspects of a service required to interact with the service.

Capability: an ability to perform a specific set of functions resulting in a real world effect.

Visability: The capacity for those with needs and those with capabilities to see each other and interact.


Core Concepts of SOA (DRAFT)

Execution Context: Set of technical/business elements that form path between those with needs and capabilities. Permits information to be exchanged, actions to be performed and provides a decision point for any policies and contracts that may be in force.

Policy: A set/range of constraints imposed on any entity when invoking a service. If ignored, the invocation request may be denied.


Core Concepts of SOA (DRAFT)

Exchange: The act whereby two or more entities come together within the context of a single interaction.

Real World Effect: The result of an interaction with a service.

Interchange: the activity of using the capability. An “act” rather than an “object”


Concepts around Visibility


Interaction with Service


Real World Effect – shared state


Service Description


Recurring Q&A…

Why are concrete things not in the reference model (security, messaging protocols etc…)?

Why don’t I see two entities in the RM (service consumer and service provider)?

How does “infrastructure” fit into the reference model?

Does the SOA reference model require definition of core infrastructure?

Why is BP* not part of SOA? (next slide)


Service

Capabilities

Service Consumers

Where do things live?

Core SOA

Business Process, State alignment, orchestration, choreography, etc..

Applications, ECM, DB, …

In a layer diagram, layer “n” is only visible to layers (n +1) and (n – 1)

Visible

Notvisible

What services are used for

Sources, functionality for capabilities


BPM is a layer over SOA.

Data

Data ServerServerServer

Server

Service

Service

Service

ServiceService

Server

Server

Courtesy Booz Allen Hamilton – http://www.bah.com

Business & Application

Tier

ServiceOriented

Tier

Business Process

Acquisition

Business Process

Human Resources

Business Process

Grants Management

Business Process

Customer Service

Business Process

Budgeting and Forecasting

Process & Orchestration

Tier

Service


Processes can be in front of OR behind services

Processes aggregate multiple services and can themselves be exposed as services.

Since services hide the resources behind them, not all details of the process may be available.

Service Process

* 1

-<<represented as>>* *

<<uses>>


About Reference

Models


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 and may be used as a basis for education and explaining standards to a non-specialist.

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.


Where would the housing industry be?

Implied reference model means architects know their blueprints will be understood and that manufacturer’s are ready to supply the parts needed.

“Palette” of items to work from in model: Doors, Windows, frames, Gyproc, Flooring, Plumbing etc. Vendors are aligned with architects views. Entire industry

wins!


Reference Models are Abstract

The RM for “house” is not specific enough for a contractor to build a house.

The RM aides the architect to make a specialized architecture for a specific set of requirements, using elements of the RM.

Most industries have an implied or explicit reference model: Automobile, Aerospace, Logistics, Bicycle, Skis, etc.


OASIS SOA RM TC

(optional slides)


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.


To develop a Reference Model for SOA

The TC is asking itself these questions: What elements are common in all implementations of SOA?

( be careful – think about this)

(Paraphrased) What are the core things that make SOA service oriented?

How do we describe those as abstract concepts?

What relationships exist amongst those concepts?

How do we represent those concepts without referencing concrete implementations.


Existing situation in Web Services

WSDL XML &SchemaSOAP

Base Standards

WS-RMWS

Addressing Reg/RepUDDI

WS-SecurityWS-Trust

WS-*

RequirementsQuestion: How do I account formy requirements and organize components when building a concrete architecture?


Thoughts on developing specific SOA’s

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 development of specific

service oriented architectures.

Model for a “way of thinking” when architecting.

Re-useable by multiple architects writing SOA for multiple domains.

Helps architects slot existing standards into their architectures.


SOA RM used for range of service oriented architectures

WSDL XML &SchemaSOAP

Base Standards

WS-RMWS

Addressing FooUDDI

WS-SecurityWS-Trust

WS-*

Requirements

Guides developments of

SOA-RM

SpecificArchitectures

Uses

Input for


References

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

Thank you – Duane Nickull, [email protected]


Documents

An Introduction to the OASIS Reference Model for Service Oriented Architecture (SOA)