1. Service Oriented Architecture Reference Model
An informal SOA Ontology

2. Reference Model
An abstract framework for understanding significant relationships among the entities of some environment.
Consists of a minimal set of unifying concepts, axioms and relationships within a particular problem domain.
Is independent of specific standards, technologies, implementations, or other concrete details.

3. Reference Model

4. Service Oriented Architecture
Service Oriented Architecture is a paradigm for organizing and utilizing distributed capabilities that may be under the control of different ownership domains.
Goal of this reference model is to define the essence of Service Oriented Architecture

5. Why Service Oriented Architecture?
Drivers:
Large scale Enterprise systems
Internet scale provisioning of services
Reduce the cost of doing business
Benefits
Build scalable, evolvable systems
Scalable because minimizes assumptions
Manage complex systems
Encourage re-use of business function 

6. Why is it different? SOA reflects the reality of ownership boundaries
CORBA, RMI, COM, DCOM, etc. all try to implement transparent distributed systems
Ownership is of the essence in SOA
SOA is task oriented
Services are organized by function
Getting something done
SOA is inspired by human organizations
It worked for us, it should work for machines

7. What is not in the RM Service composition Organizational framework
Choreography, orchestration
Process Oriented Architecture
Organizational framework
Who is doing what to whom
Specific technologies
not even specific architectures

8. Key concepts

9. Service A mechanism to enable access to one or more capabilities
using a prescribed interface
consistent with constraints and policies as specified by the service description.

10. Visibility Awareness Willingness Reachability
Visibility is the relationship between service participants that is satisfied when they are able to interact with each other
Awareness
Service description
Discovery
Willingness
Policy & contract
Reachability
Communication

11. Interaction
Interacting with a service involves performing actions against the service
The extent to which one system can effectively interpret information from another system is governed by the
semantic engagement of the various systems.
The semantic engagement of a system is a relationship between the system and information it may encounter.

12. Real World Effect
The purpose of using a capability is to realize one or more real world effects.
At its core, an interaction is “an act” as opposed to “an object” and the
result of an interaction is an effect (or a set/series of effects).
The real world effect is couched
in terms of changes to the state shared by
the participants and stakeholders in
a service interaction

13. About Services

14. Conditions and Expectations
Policy
Constraint representing the intention of a participant in a service
Contract
Constraint representing an agreement between two or more participants.

15. Description The service description represents the information
needed in order to use, manage or provide a service.
Service reachability
Service Functionality
Service Policies
Service Interface

16. Execution Context
The execution context is the set of infrastructure elements,
process entities, policy assertions and agreements that are
identified as part of an instantiated service interaction,
and thus forms a path between those with needs and those
with capabilities

17. Is a Reference Model an Ontology?
Establishing a vocabulary
A lot of definitions
The RM glossary has 28 entries
Formality was considered
Audience is not formal
Mechanical processing of RM not expected

18. What about UML UML obvious choice for an architecture spec But,
Inheritance (is-a) relationship almost never used
Extraneous precision
E.g. we tried to define Service, not count the number of service providers
It’s so ugly <duck/>

19. An early concept map

20. Concepts Maps
Concepts maps were excellent graphical indices to text
Concepts, and relationships. All we needed

21. On the cutting-room floor…

22. Where we are Committee Specification published
Reference Architecture effort started