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OASIS Service Oriented Architecture Reference Model Technical Committee (SOA-RM)
BOOT CAMPApril 13 2005
DRAFT: Not approved by the OASIS SOA RM TC.
Purpose
• This slide deck is designed to bring new TC members up to speed.
• Work described herein defines what we have consensus on at present time.
• CAVEAT: Subject to change in future
Agenda
• What is SOA; what is a reference model for SOA• Why is a reference model needed• The OASIS SOA RM TC
Defining SOA
• If Service Oriented Architecture is Architecture, as the name implies, it should be definable as architecture.
• This should not be done by referencing specific implementations.
• Definition of Architecture (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 software architecture.– Focus herein is “software & systems architecture”
• “Services” are the central concept; other concepts are present.
• SOA not currently defined other than a “common law” or “defacto” perception of what it is.
• Perceptions for definition of SOA are vastly disparate.
What is a SOA Reference Model?
• Is a model for developing a range of Service Oriented Architectures and analysis/comparison thereof.
• Is not architecture for a single implementation. This is very important to understand since things you may see in other architecture might not be present in the Reference Model.
• Is a framework for understanding significant relationships among the elements of a SOA environment.
• Is based on concepts present in all SOA’s. • A Reference Model defines SOA in an abstract sense.
Example:• Abstract = Service Description• Concrete = WSDL
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.
Base Components
• Service: A behavior, or set of behaviors provided for use by another entity.
• Service Description: A specification of the information necessary to:– allow a potential consumer to determine whether or
not this service is applicable, and
– facilitate invocation. • Advertisement: A methodology to convey
awareness of (the existence of) a service(s) to all consumers on a fabric. Advertising makes discovery possible.
Base Components and Concepts of SOA
• Data Model:The logical expression of a set of information items associated with the consumption of a service or services.
• Contract: The syntactic, semantic and logical constraints governing on the use of a service.
SOA Axioms
• A Service is a set of functionality provided by one entity for the use of others.
• Services are conceptually autonomous (self sufficient) and opaque (independent of underlying technology) in nature.
• There is no need to make architectural distinctions between services that are consumed as part of a process vs. ones that are not.
• There is not a one to one correlation between requests to invoke a service and instances of a service being consumed.
• Each logical Service has exactly one canonical Service Description.
SOA Axioms
• 6. A Service Description is comprised of three logical parts– Data Model - The logical expression of a set of information items
associated with the consumption of a service or services;– Policy - Assertions and obligations that service consumers
and/or providers must adhere to or provide; and– Contract (and/or offer thereof) - the syntactic, semantic and
logical constraints governing on the use of a service.
• 7. A security policy is a specialized type of the Service Description policy noted above.
• 8. Service Policy may mandate security requirements to be met, and if they are not, interaction (with the service) may be refused.
SOA Axioms
• 8. A null security policy is still logically considered a policy.
• 9. A Service Description is advertised to consumers on a fabric to make it discoverable.
• 10. Discovery does not constitute authorization to execute against the service.
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 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 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
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.
Other orientation activities
• Review member submissions in our document repository.
• Review glossary - http://www.tekni.ca/twiki/bin/view/SoaRefModel/SoaReferenceModelGlossary
• Review SOA axioms - http://www.oasis-open.org/apps/org/workgroup/soa-rm/download.php/12246/SOA%20Axioms.pdf
• Review message archives.
Links to non-related Reference Models
• 1. http://www.isotopicmaps.org/TMRM/TMRM-latest.html• Short and to the point. A good demonstration of how efficient and small a
good reference model can be.• 2. http://www.isotopicmaps.org/tmrm/rm20031014.pdf• A Mathematical formula of the above Reference Model for Topic Maps• 3. http://www.dpconline.org/docs/lavoie_OAIS.pdf• The OAIS Reference Model overview. Another good example of a small,
compact, lean reference model.• 4.
http://www.x12.org/x12org/comments/X12Reference_Model_For_XML_Design.pdf
• X12 reference model for XML. 120 pages – more technical.• 5. http://www.digitalearth.gov/derm/v05/derm05.pdf• This reference model actually brings together implementation technologies
with abstract concepts.• 6. http://www.wfmc.org/standards/docs/tc003v11.pdf• Workflow Reference Model that includes specific technology – 55 pages