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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.
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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).
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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.
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How does a RM relate to other stuff?
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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.
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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.
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Additional Service concepts
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Core Concepts for SOA - expanded
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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.
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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.
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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”
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Concepts around Visibility
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Interaction with Service
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Real World Effect – shared state
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Service Description
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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)
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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
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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
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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>>
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About Reference
Models
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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.
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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!
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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.
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OASIS SOA RM TC
(optional slides)
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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.
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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.
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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.
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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?
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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.
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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
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References
OASIS SOA RM TC - http://www.oasis-open.org/committees/tc_home.php?wg_abbrev=soa-rm
Thank you – Duane Nickull, [email protected]
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