RE: [soa-rm] Definition: Services

["Peter F Brown" <peter@justbrown.net>]

+1

I'm a little worried at the drill-down into very tightly defined but
technically oriented language being proposed for some of the "real world"
terms that we want to use in a reference model.
We have agreed that that we consider the reference model to be scoped for
software development rather than anything else, but nonetheless I think that
the reference terminology needs to be understood and accepted beyond the
software and process modelling communities

Peter

| -----Original Message-----
| From: George Ntinolazos [mailto:georgios.ntinolazos@stratasoftware.com]
| Sent: Wednesday, April 13, 2005 9:40 AM
| To: 'Duane Nickull'
| Cc: mattm@adobe.com; soa-rm@lists.oasis-open.org
| Subject: RE: [soa-rm] Definition: Services
| 
| Duane, Matt
| 
| What is the 'thing' that you refer to as a 'service'? Is the service a
| 'thing' in the 'real' world, the WSDL file in the hard drive, or the
| binary
| loaded in the VM or ...? Can you give an example?
| 
| What I am trying to say is that we need to either qualify the term service
| or use alternative terms to distinguish the different forms/views of a
| service thought its lifecycle.
| 
| George
| 
| 
| -----Original Message-----
| From: Duane Nickull [mailto:dnickull@adobe.com]
| Sent: 12 April 2005 17:13
| To: George Ntinolazos
| Cc: 'Don Flinn'; soa-rm@lists.oasis-open.org
| Subject: Re: [soa-rm] Definition: Services
| 
| George:
| 
| Going back to the W3C Technical Note, one of the core principles of
| services is that they are autonomous.  They do not care whether they are
| part of a business process or any other process.  They are self
| sufficient atoms.  The concepts of BPM really belong in a POA reference
| model (which no one has done to my knowledge) or a process oriented view
| of a specific architecture, not in a reference model for service
| oriented architecture.
| 
| Perhaps we should ask the editors to consider this sentence as a
| placeholder:
| => There is no need to make architectural distinctions between a service
| that is consumed as part of a process vs. one that is not.
| 
| I would also assert that a specific architecture can concurrently be
| both SOA and POA.
| 
| Furthermore, another key concept of the W3C WSA is that services are
| independent from underlying implementation technology.  If we start
| looking at the specific function()'s , including one service that
| functionally calls 2 others, we are violating this principle.
| 
| I would like to ask the editors to keep this sentence as a placeholder
| too:
| => Services are opaque and independent from underlying technology.
| 
| Both of these concepts need to be completely abstract to be included in
| the RM.
| 
| Duane
| 
| George Ntinolazos wrote:
| 
| >I think, in our attempt to define what a service is, we will need to
| >distinguish between the world of business processes and the software
| world
| >which automates some aspects of those processes. (Here by business, I
| mean
| >the domain of interest or problem domain)
| >
| >This distinction will allow for qualified terms such as business service,
| >software service, and functional service:
| >
| >A business service represents a step or set of steps within a business
| >process that is atomic and potentially fully automatable. For example, an
| >openAccount business process may contain an atomic step such as
| >identifyCustomer which is a business service.
| >
| >A functional service is a software service which automates all, or part,
| of
| >a business service. A functional service is an abstraction which defines
| the
| >contractual aspects of a service independently of the implementation
| >technology choices. By definition, is always 'business' focused.
| >
| >A technology service is the realization of all, or part, of a functional
| >service in a given implementation technology. For example, a Java
| operation
| >invoked using RMI, or a Web Service could both be elements of technology
| >services.
| >
| >
| >A second important distinction is between design-time and runtime. At
| >runtime, objects that offer services may be associated with state.
| Consider
| >the indetifyCustomer software service. At runtime this software may be
| >associated with more than one set of customers, that is, it might be
| >deployed multiple times pointing to different data. Is this one service
| or
| >many?
| >
| >Yet another aspect we need to take into account is the service
| granularity.
| >A service specification can be represented at a number of candidate
| levels
| >ranging from a typed set of operations (usually referred to as an
| >interface), to the more abstract notion of a set of such interfaces.
| >Further, some existing definitions of service refer to the set of
| interfaces
| >which constitute a particular interaction between parties (for example a
| >CORBA service or a WSDL composition), whereas some focus on the
| >responsibilities of a particular party (or role) within that interaction
| >(Design by Contract approach).
| >
| >George
| >______________________________________
| >George Ntinolazos BSc(Hons), MSc, MBCS
| >
| >Product Director
| >Strata Software Ltd.
| >Office: +44 (0)1483 422515
| >Mobile: +44 (0)7966 652063
| >www.stratasoftware.com
| >Best Practice for Service-Oriented Architectures
| >
| >
| >
| >
| >-----Original Message-----
| >From: Duane Nickull [mailto:dnickull@adobe.com]
| >Sent: 11 April 2005 20:31
| >To: Don Flinn
| >Cc: soa-rm@lists.oasis-open.org
| >Subject: Re: [soa-rm] Definition: Services
| >
| >I do not like this definition since it assumes that all services are
| >used for business processes, which is simply not true.
| >
| >I liked Matt's definition from this morning or some variation of it.  We
| >had one from the SOA Q&A we did and referenced it form the charter.  Not
| >sure if this one still works or if it rubs folks the wrong way.
| >
| >Q: What is a service?
| >
| >A: A service is a contractually defined behavior provided by a component
| >for use by other component(s) based on the contract.
| >
| >Google had too many definitions ranging from Church services to
| >implementation specific definitions.  Didn't find anything there that
| >was abstract.
| >
| >I tried to write another one:
| >
| >Service: an externally visible behavior of a component offered for
| >consumption by other components.  not happy with that.
| >
| >The W3C technical note had a pretty interesting definition, albeit once
| >more implementation specific to WS*:
| >
| >
| >          2.3.2.10 Service
| >
| >
| >            2.3.2.10.1 Definition
| >
| >A service is an abstract resource that represents a capability of
| >performing tasks that represents a coherent functionality from the point
| >of view of provider entities
| ><http://www.w3.org/TR/2004/NOTE-ws-arch-20040211/#provider_entity> and
| >requester entities
| ><http://www.w3.org/TR/2004/NOTE-ws-arch-20040211/#requester_entity>. To
| >be used, a service must be realized by a concrete provider agent
| ><http://www.w3.org/TR/2004/NOTE-ws-arch-20040211/#provider_agent>.
| >
| >
| >            2.3.2.10.2 Relationships to other elements
| >
| >a service is a <http://www.w3.org/TR/2004/NOTE-ws-arch-20040211/#isa>
| >
| >    resource <http://www.w3.org/TR/2004/NOTE-ws-arch-20040211/#resource>
| >
| >a service performs
| >
| >    one or more tasks
| >    <http://www.w3.org/TR/2004/NOTE-ws-arch-20040211/#service_task>
| >
| >a service has <http://www.w3.org/TR/2004/NOTE-ws-arch-20040211/#hasa>
| >
| >    a service description
| >    <http://www.w3.org/TR/2004/NOTE-ws-arch-
| 20040211/#service_description>
| >
| >a service has a <http://www.w3.org/TR/2004/NOTE-ws-arch-20040211/#hasa>
| >
| >    service interface
| >    <http://www.w3.org/TR/2004/NOTE-ws-arch-20040211/#service_interface>
| >
| >a service has <http://www.w3.org/TR/2004/NOTE-ws-arch-20040211/#hasa>
| >
| >    service semantics
| >    <http://www.w3.org/TR/2004/NOTE-ws-arch-20040211/#service_semantics>
| >
| >a service has <http://www.w3.org/TR/2004/NOTE-ws-arch-20040211/#hasa>
| >
| >
| >
| >
| >
| >
| >Duane
| >
| >Services:
| >
| >Don Flinn wrote:
| >
| >
| >
| >>I just ran across a definition of a service in the paper "Composition
| >>Contracts for Service Interaction" Andrade, L. and Fiadeiro, J., which
| >>looks good.
| >>
| >>Slightly modified -
| >>Services are granular software components that can be used as building
| >>blocks for the assembly of business processes.
| >>
| >>Original -
| >>Services can be seen as granular software components that can be used as
| >>building blocks for distributed applications or for the assembly of
| >>business processes.
| >>
| >>Don
| >>
| >>
| >>
| >>
| >>
| >
| >
| >
| 
| --
| ***********
| Senior Standards Strategist - Adobe Systems, Inc. - http://www.adobe.com
| Vice Chair - UN/CEFACT Bureau Plenary - http://www.unece.org/cefact/
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