Turning Software Turning Software into a Serviceinto a Service

By Mark Turner, David By Mark Turner, David Budgen and Pearl BreretonBudgen and Pearl Brereton

Two MajorThemesTwo MajorThemes

• The promotion of Software as a The promotion of Software as a service (SaaS)service (SaaS)

• The proposal a change to the way The proposal a change to the way software development is created software development is created through Service compositionthrough Service composition

Quick DefinitionsQuick Definitions•SaaSSaaS

–Software provided by a third party from a remote Software provided by a third party from a remote location. location.

–One instance servicing many users. One instance servicing many users. – It focuses on separating possession and It focuses on separating possession and ownership from software useownership from software use

•Service CompositionService Composition–The construction of software from many smaller The construction of software from many smaller components provided by several providers at components provided by several providers at remote locationsremote locations

Services Offered

Translation Services AvailableTranslation

Services Available (Broker)

Service Composition Service Composition ExampleExample

Alice Company

Properties Info

Negotiation

And

Purchasing

- Scribe

-TS2

- TS3

- TS4

- LTS1

- ES-Trans

- LTS3

Unknown to Alice

BenefitsBenefits

• Services can change when the Services can change when the business changes dynamicallybusiness changes dynamically– i.e. scribe broker discovers new servicei.e. scribe broker discovers new service

• Example shows two examples of Example shows two examples of service discovery and two stages of service discovery and two stages of service negotiationservice negotiation

• a service is only concerned with a service is only concerned with issues around the sub services it is issues around the sub services it is subscribed tosubscribed to

Service ModelsService Models

Supplier’s Software

Application Service

Service Transportation Layer (using forms such as .net or J2EE)

Layer 1

Layer 2

Layer 1

Layer 2

Layer 3

Service Layer (Applications created on demand from smaller services)

Service Integration Layer

Service Transportation Layer

Current Supply Led Model Proposed Demand Led Model

Integration LayerIntegration Layer

• The key to the integration layer are The key to the integration layer are divided into the following sub layers.divided into the following sub layers.– Service descriptionService description – Service discoveryService discovery – Service negotiationService negotiation – Service deliveryService delivery – Service compositionService composition

Integration Layer- Service Integration Layer- Service DescriptionDescription

• Current service description methods do not Current service description methods do not describe function semantically. describe function semantically.

• WSDL is the standard protocol for describing WSDL is the standard protocol for describing services but it does not have a feature for services but it does not have a feature for describing the functions negotiable describing the functions negotiable parameters such as cost, duration, contract, parameters such as cost, duration, contract, termination rules, etc. termination rules, etc.

• The Agent Markup Language for Services The Agent Markup Language for Services (DAML-S now called OWL-S) is a markup (DAML-S now called OWL-S) is a markup language for describing the properties and language for describing the properties and capabilities of Web services in unambiguous, capabilities of Web services in unambiguous, computer-interpretable form. computer-interpretable form.

• This is an important protocol to this model This is an important protocol to this model because it is the only protocol that describes a because it is the only protocol that describes a service in this detail.service in this detail.

Integration Layer- Service Integration Layer- Service Discovery Discovery

• This service allows a client to identify This service allows a client to identify potential service providers that offer a potential service providers that offer a function that meets their needs and that are function that meets their needs and that are prepared to negotiate within some prepared to negotiate within some acceptable bounds. acceptable bounds.

• Although UDDI is the standard for Although UDDI is the standard for discovering services it does not allow for discovering services it does not allow for services to be discovered using its semantic services to be discovered using its semantic description. description.

• This semantic description ties in with the This semantic description ties in with the need for Service description have semantic need for Service description have semantic descriptions of the functions. descriptions of the functions.

Integration Layer- Service Integration Layer- Service Negotiation Negotiation

• This deals with clients and service This deals with clients and service providers negotiating on the terms providers negotiating on the terms and conditions of the client using the and conditions of the client using the providers service. providers service.

• Only ebXML allows for automatic Only ebXML allows for automatic negotiation and contracting negotiation and contracting

Integration Layer- Service Integration Layer- Service Delivery Delivery

• This service addresses the need for This service addresses the need for checking to see if the negotiated terms checking to see if the negotiated terms were filled and withheld during its use.were filled and withheld during its use.

• Were all conditions and provisions Were all conditions and provisions meet? meet?

• Using ebXML’s has a contract and Using ebXML’s has a contract and CPA document that monitors CPA document that monitors transactions and terminates the transactions and terminates the process if the contract is broken. process if the contract is broken.

Integration Layer- Service Integration Layer- Service Composition Composition

• By using the protocols at various By using the protocols at various layers of the model web services are layers of the model web services are automatic composed and bound.automatic composed and bound.

• The Business Process Modeling The Business Process Modeling Language or the Business Process Language or the Business Process Execution LanguageExecution Language for web for web services can be used to model the services can be used to model the control and data flows between control and data flows between services that were bound. services that were bound.

Proposed Web Services Stack Proposed Web Services Stack Framework.Framework.

ebXML SpecsSemantic WebExtend WSDL

ConclusionConclusion

• The important layers deal with the The important layers deal with the coordination of many smaller services to coordination of many smaller services to compose the main service that will fill a compose the main service that will fill a required need. required need.

• Although the model seems complicated Although the model seems complicated we must be remembered is that the we must be remembered is that the model is trying to accomplish these takes model is trying to accomplish these takes dynamically in real time as the request dynamically in real time as the request for the service is realized. for the service is realized.