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IBM Research
© 2008 IBM Corporation
The Myth and Reality of (Automated) Web Services Composition
Dr. Biplav Srivastavahttp://www.research.ibm.com/people/b/biplav/
IBM T. J. Watson Research Center, USA and India Research Lab, India
Major Collaborators: IBM Research Labs: India, Watson, Zurich; Arizona State University; DAGSTHL Seminar 07061;
University of Georgia, AthensASU: April 2008
IBM Research
© 2008 IBM Corporation2 The Myth and Reality of Web Services Composition
Outline
IT Issues Faced by Businesses Today
Web Services Composition – What is it and Why is it Important– Basics– Typical scenarios
A model for understanding different approaches– Suitability of approaches for different scenarios– Examples
An Update on Progress in Automated WSC– Myth: Resolve scale-up and search issues for WSC composition – Reality: Resolve composition set-up issues (at problem set-up or solving phases)
Emerging Trends – Plan reuse and modification in the context of richer, but unstructured, domain models – Planning in the presence of impoverished domain models: model-lite planning
Conclusion
IBM Research
© 2008 IBM Corporation3 The Myth and Reality of Web Services Composition
Major IT Issues Faced by Businesses Today
Business-IT alignment– Are my investments in IT supporting my business?
– Can my investment in IT give competitive edge?
Enterprise Application Integration– Integrating across divisions in the same company
– Integrating with suppliers, partners
Collaboration– Perennial, new global dimension
Asset Reuse– Software reuse is perennial
– Documents, methods, even presentations
IBM Research
© 2008 IBM Corporation4 The Myth and Reality of Web Services Composition
Background: Web Services Service Broker
Service Provide
r
Service Requester
WSDLSearch with UDDI and get WSDL of match
Invoke using SOAP
Execute BPEL
Return Solution
What is the service representation?
(Advertised) Instances: A service that can be invoked at a physical URL. It is represented by WSDL. Some semantic representations can compete in this space (OWL-S).
Deployed and Running Instances: Not all advertised services may be running at a given execution time.
Type: Collection of services sharing common capabilities (what they do) but differing in how to access them. Semantic representations should capture this.
IBM Research
© 2008 IBM Corporation5 The Myth and Reality of Web Services Composition
A Simple Web Service Composition Scenario
S1
S2
S3
Requester
Search with Requirement
S1 -> S3
…
Service Registry
Composition
Module
S1 S3
Execute based on Composition
Centralized v/s Decentralize Orchestration(S1 could have sent output to S3 directly)
IBM Research
© 2008 IBM Corporation6 The Myth and Reality of Web Services Composition
The Potential of WSC Depends on What is a Service?
Service As Business Benefit CS Areas (in addition to AI!)
Online, Deployed Applications
Mashups, Collaboration, New Revenue Streams, Data Integration
User Interfaces, Visualization, Databases/ Streaming
IT Systems EAI Metadata Management, Distributed Systems, Messaging/ Networking
Software Components Software Reuse Software Engineering, Databases
Business Processes Business-IT alignment Business Process, Management Metrics
IBM Research
© 2008 IBM Corporation7 The Myth and Reality of Web Services Composition
Case Study: Application Integration
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© 2008 IBM Corporation8 The Myth and Reality of Web Services Composition
Telco Ecosystem
Service/content providers are often 3rd parties
Telco is the intermediary for delivery of services to enterprises/consumers
– Must improve ease-of-use of its software infrastructure
– Must optimize the utilization of its IT infrastructure
Need to adopt standards-based framework
– Use Web services to build end-user services
– Use semantic annotations allowing service functionality to be programmatically composed
3rd PartyProviders
Telco Enterprise
User
User
User
IBM Research
© 2008 IBM Corporation9 The Myth and Reality of Web Services Composition
Composed Service: Helpline Automation
Problem Reporting
RegistryUpdate
CallSetup
Help Desk
MessageDelivery
On Site
Problem Classification
Location-basedAgent Selection
Expert LookupAgent Assignment
Desk-based Expert ID Field Expert ID
Problem Ticket
Problem Ticket, Problem Ticket,
Resolution StatusProblem Ticket,
Resolution StatusProblem Ticket,
Customer Interaction
Top-down or bottom-up
Source: A Service Creation Tool Based on End-to-End Composition of Web Services. V. Agarwal et al, WWW 2005
IBM Research
© 2008 IBM Corporation10 The Myth and Reality of Web Services Composition
Creation of a new service
Main IssuesScalability of composition solutionLevel of automationModeling domain informationLeverage industry practices
Specify end-user service capability
Select service providers
Design theflow
Deploy theservice
New service
capabilities
New service
providers
Network / environment
changes
• Manual business process integration
• Use tools like WSAD-IE to create flows and business logic
• Deploy using a flow engine (such as MQWF / WBI SF)
Source: A Service Creation Tool Based on End-to-End Composition of Web Services. V. Agarwal et al, WWW 2005
IBM Research
© 2008 IBM Corporation11 The Myth and Reality of Web Services Composition
Synthy System Architecture
Abstract Workflow
(Plan)
Domain Ontolog
y
Service Registry
DeployableWorkflow
ServiceSpecificatio
n
Logical Composer
Physical Composer
Execution Environment
Service CreationEnvironment
Key Components
– Service Capabilities Database
• Information about services available in-house as well as with 3rd party providers
– Telecom Ontology
• Domain-specific terminology
– Logical Composer including Planner
• automated aggregation of services via generative planning-based reasoning techniques
– Physical composer
• Instance selection based on end to end QoS specification
Input
– Requirements document for the new service that needs to be composed
Output
– Deployable workflow representing a composite service
Synthy: http://domino.research.ibm.com/comm/research_people.nsf/pages/biplav.Synthy.html
IBM Research
© 2008 IBM Corporation12 The Myth and Reality of Web Services Composition
Synthy IDE
An IDE needs to support several views each applicable to a different kind of role– Service Requester
– Service Developer
– Deployment Engineer
– Administrator
Different technological and Interface Requirements
Service Requester
Administrator
Deployment EngineerService Developer
WebServiceRqmt.
ServiceDiscovery
ServiceSelection
ServiceAggregation
ServiceDeploy--ment
CompositeService
OWL-S,WSDLBPEL BPEL
OWL-S
IBM Research
© 2008 IBM Corporation13 The Myth and Reality of Web Services Composition
Synthy IDE: Problem Description Lack of Service Composition tools
– tooling available for creation of web services
– existing prototypes handle only part of the problem
– Need for an Integrated Development Environment (IDE) to ease the process of composition, thereby reducing development time and integration efforts
Tooling Challenges– web services are actively running entities that need to be composed together
– new web services may come up or old ones may go down dynamically, leading to much more frequent changes than in traditional software libraries or components
– the tool should be able to work with components in the runtime environment in addition to offline development modules
– has implications on functionality, interface, performance and runtime behavior of the IDE
IBM Research
© 2008 IBM Corporation14 The Myth and Reality of Web Services Composition
Case Study: Online Data Aggregation
IBM Research
© 2008 IBM Corporation15 The Myth and Reality of Web Services Composition
Travel Reservation Problem
Source: Getting from Here to There:. Interactive Planning and Agent. Execution for Optimizing Travel. José Luis Ambite et al, IAAI 2002
Online information services– Services are data sources; can be modeled as databases which can be queried with no, or controlled, side-effects– Composite service should be responsive but accuracy can be negotiated– Services are heterogeneously owned, hence relatively autonomous in choosing specifications
IBM Research
© 2008 IBM Corporation16 The Myth and Reality of Web Services Composition
Source: Getting from Here to There:. Interactive Planning and Agent. Execution for Optimizing Travel. José Luis Ambite et al, IAAI 2002
Workflow Templates
IBM Research
© 2008 IBM Corporation17 The Myth and Reality of Web Services Composition
Case Study: Mashup Advisor
IBM Research
© 2008 IBM Corporation18 The Myth and Reality of Web Services Composition
MashUp Advisor Summary*
MashupAdvisor exploits a repository of mashups to provide design-time assistance to the user through relevant suggestions as to what outputs can be generated along with the best plans to generate those outputs. The system has two components: an output ranker, which ranks the outputs based on their popularity scores, and a planner, which uses metric planning algorithms and a configurable utility function. The system takes into account popularity and semantic similarity when recommending services and sources.
Main Contributions:– Recommends new outputs to enrich the mashup– Generates better plans by reusing knowledge built by other users– Saves development time by automatically recommending and linking services
Link to demo
Team: Hazem Elmeleegy Anca Ivan, Rama Akkiraju, Richard GoodwinExtended Team: Biplav Srivastava
IBM Research
© 2008 IBM Corporation19 The Myth and Reality of Web Services Composition
System Architecture
MashupA
Repository Manager
CatalogueManager Mashup
Repository
Domain Ontology
StatisticsManager
Semantic Matcher
Output Ranker
Planner
Thesaurus
Mashup Editor Server
(Fusion Server)
Partial Mashup
Ranked Output List
Desired Output
Partial Mashup
Minimum Cost Plan
MashupAdvisor
Mashup Editor Client
(Fusion Client)
Internet
IBM Research
© 2008 IBM Corporation20 The Myth and Reality of Web Services Composition
A Framework for Understanding WSCE
IBM Research
© 2008 IBM Corporation21 The Myth and Reality of Web Services Composition
A Model for WSCE*
An Overall Web Service Composition and Execution view is important in practice
Web ServiceComposition and
Execution
Specification of Requirement
Available Capabilities
[ Templates, Policies ]
ExecutionTrace
Today, it is not clear what are fundamentally different possible types of WSCE approaches and which type to use in a given scenario?
Events
*Services are assumed to be stateless
IBM Research
© 2008 IBM Corporation22 The Myth and Reality of Web Services Composition
Basis for WSCE approaches Are composition and execution separable?
– No, Yes
When does composition happen?– Offline, Online
How does composition happen?– Search-based, Template-based
What information is used for composition?– Service types, Service instances published, Services deployed, Templates/ Policies
How are external events handled at runtime (adaptation)?– On-the-fly, gradual
IBM Research
© 2008 IBM Corporation23 The Myth and Reality of Web Services Composition
Search-based Composition Execution
Specifications
X={x1,x2,…x}
T={t1,t2,…t}
Interleaved Approach
On-line
Events
Example: ConGolog, Heracles+Theseus
IBM Research
© 2008 IBM Corporation24 The Myth and Reality of Web Services Composition
Monolithic Composition
RuntimeSpecifications
I={i1, i2,… i} X={x1,x2,…x}
W={W1,W2,…WL}
T={t1,t2,…t}
FRE
RIWREW
Monolithic Approach
Off-line On-line
Events
≥
Example: SWORD, SHOP-2 based, Petrinet-based, Astro, METEOR-S
IBM Research
© 2008 IBM Corporation25 The Myth and Reality of Web Services Composition
Logical Composition
PhysicalComposition
RuntimeSpecifications
C={c1,c2,…c} I={i1, i2,… i}
S={S1,S2,…SK} W={W1,W2,…WL}
T={t1,t2,…t}
FPC FRE
RAW RIWREW
Staged Approach
Off-line On-lineOff-line
X={x1,x2,…x} Events
≥
Example: Synthy, Self-Serv with web communities (but informal modeling)
IBM Research
© 2008 IBM Corporation26 The Myth and Reality of Web Services Composition
Template-based Approach: Creation of a Template
T= {t1,t2,…t}
W={W1,W2,…WL}
S={S1,S2,…SK}
Generalize: remove commitments to get templates
Tem
plates
Staged
Monolithic
Interleaved
Traces
Executable Workflow
Abstract Workflow
IBM Research
© 2008 IBM Corporation27 The Myth and Reality of Web Services Composition
Usage of a Template
T= {t1,t2,…t}
Tem
platesW={W1,W2,…WL}
S={S1,S2,…SK}
Staged
Monolithic
Interleaved
Traces
Executable Workflow
Abstract Workflow
Add commitments to generate workflow or trace (Assign values to template parameters)
WSCE
Example: Heracles+Theseus, METEOR-S (Semantic templates, other templates),template-based planning
IBM Research
© 2008 IBM Corporation28 The Myth and Reality of Web Services Composition
Basis for WSCE approaches Are composition and execution separable?
– No, Yes
When does composition happen?– Offline, Online
How does composition happen?– Search-based, Template-based
What information is used for composition?– Service types, Service instances published, Services deployed, Templates/ Policies
How are external events handled at runtime (adaptation)?– On-the-fly, gradual
Separable? When How What How
Interleaved No Online Search Services deployed On-the-fly
Monolithic Yes Offline Search Services instances published Gradual
Staged Yes Offline Search Service types, Service instances published
Gradual
Template Yes Offline, Online
Template Templates/ policies, Services instances published, deployed
On-the-fly, Gradual
IBM Research
© 2008 IBM Corporation29 The Myth and Reality of Web Services Composition
Comparing Approaches
Interleaved Monolithic Staged Template
Composition Effort
O(λ)O(βλ)
Min: O(λ)O(αλ + Mλ) O(Mλ )
Composition Control
NoneLow:
< RIW; FE >
High:
< RAW;RIW; FC; FE >
High:
<template, underlying composition method>
Ability to Handle Composition
FailureNone Low High Low
Adaptation during Execution
High Medium Medium Low to Medium
Information Modeling
Simple (Instances)
Simple (Instances)Elaborate (Types and Instances)
Elaborate (Templates and Instances)
LimitationSearch should be dead-end
free
Always a time-lag between service
information offline v/s online
Always a time-lag between service
information offline v/s online
Search restricted by template – can cause INCOMPLETENESS; Any restriction of the
underlying composition method
Details in: Understanding approaches for web service composition and execution, Vikas Agarwal, Girish Chafle, Sumit Mittal, Biplav Srivastava, ACM COMPUTE 2008
IBM Research
© 2008 IBM Corporation30 The Myth and Reality of Web Services Composition
Two Common Web Service Composition and Execution (WSCE) Scenarios
Online information services– Services are data sources; can be modeled as databases which can be queried with no,
or controlled, side-effects
– Composite service should be responsive but accuracy can be negotiated
– Services are heterogeneously owned, hence relatively autonomous in choosing specifications
– Sub-scenarios:• Comparison product review/ shopping sites, Online travel booking• Mash-ups: ad-hoc data services created by users
Enterprise Application Integration– Services are applications; can be modeled as programs with or without side-effects
– Composite service should accurate but responsiveness can be negotiated
– Services are more homogeneously owned (e.g., intranet); hence some control in choosing specifications can be exercised
– Sub-scenarios:• Service creation to connect internal or partner organizations• Scientific workflows: bioinformatics, Geological sciences
IBM Research
© 2008 IBM Corporation31 The Myth and Reality of Web Services Composition
Selecting an Approach for Online Scenario Online information services
– Services are data sources; can be modeled as databases which can be queried with controlled side-effects at the time of purchase
– Composite service should be responsive but accuracy can be negotiated– Services are heterogeneously owned, hence relatively autonomous in choosing
specifications
Interleaved Monolithic Staged Template
Composition Effort O(λ)O(βλ)
Min: O(λ)O(αλ + Mλ) O(Mλ )
Composition Control NoneLow:
< RIW; FE >
High:
< RAW;RIW; FC; FE >
High:
<template, underlying composition method>
Composition Failure Resolution
None Low High Low
Adaptation High Medium Medium Low to Medium
Information Modeling Simple (Instances) Simple (Instances)Elaborate (Types and
Instances)Elaborate (Templates and
Instances)
LimitationSearch should be dead-
end free
Always a time-lag between service information offline
v/s online
Always a time-lag between service
information offline v/s online
Search restricted by template – can cause
INCOMPLETENESS; Any restriction of the underlying
composition method
IBM Research
© 2008 IBM Corporation32 The Myth and Reality of Web Services Composition
Selecting an Approach for EAI Scenario
Scalability – with number of services Adaptability – to changes Failure Resolution User Interaction – control and supervision important
Interleaved Monolithic Staged Template
Composition Effort O(λ)O(βλ)
Min: O(λ)O(αλ + Mλ) O(Mλ )
Composition Control NoneLow:
< RIW; FE >
High:
< RAW;RIW; FC; FE >
High:
<template, underlying composition method>
Composition Failure Resolution
None Low High Low
Adaptation High Medium Medium Low to Medium
Information Modeling Simple (Instances) Simple (Instances)Elaborate (Types and
Instances)Elaborate (Templates and
Instances)
LimitationSearch should be dead-
end free
Always a time-lag between service information offline
v/s online
Always a time-lag between service
information offline v/s online
Search restricted by template – can cause
INCOMPLETENESS; Any restriction of the underlying
composition method
IBM Research
© 2008 IBM Corporation33 The Myth and Reality of Web Services Composition
An Update on Progress in Automated WSC
IBM Research
© 2008 IBM Corporation34 The Myth and Reality of Web Services Composition
Tracing Trends by References
Logic/ Constraints/ Planning– Semantic Web Services , McIlraith, S., Son, T.C. and Zeng, H. IEEE Intelligent Systems. Special Issue on the Semantic Web.
16(2):46--53, March/April, 2001. Copyright IEEE, 2001.– SWORD: A Developer Toolkit for Web Service Composition, Shankar R. Ponnekanti and Armando Fox, WWW 2002– Getting from Here to There:. Interactive Planning and Agent. Execution for Optimizing Travel, José Luis Ambite et al, 2002.
Web Service Composition - Current Solutions and Open Problems, B. Srivastava and J. Koehler, 2003
Semantics, Planning, Model Checking– Semi-automatic Composition of Web Services using Semantic Descriptions, E. Sirin, James Hendler and Bijan Parsia,2003
– Planning and Monitoring Web Service Composition, Pistore et al, 2004
– Automated Composition of Semantic Web Services into Executable Processes, P. Traverso and M. Pistore, 2004
Semantics, Planning, Non Functional requirements– A Service Creation Tool Based on End-to-End Composition of Web Services, V. Agarwal et al, 2005
– Planning with Templates, IEEE Intelligent Systems special issue, 2005
Web Service Composition as Planning, Revisited: In Between Background Theories and Initial State Uncertainty, J. Hoffmann, P. Bertoli, M. Pistore, AAAI 2007.
Understanding approaches for web service composition and execution, Vikas Agarwal, Girish Chafle, Sumit Mittal, Biplav Srivastava, ACM COMPUTE 2008
Domain Specific, Adaptation– SewNet - A Framework for Creating Services utilizing Telecom Functionality, WWW 2008
– Dagstuhl Seminar on Autonomous and Adaptive Web Processes, http://www.dagstuhl.de/programm/kalender/semhp/?semnr=07061
IBM Research
© 2008 IBM Corporation35 The Myth and Reality of Web Services Composition
Myth – WSC is Planning and Readily Solvable!
Resolve scale-up and search issues, and WSC will be solved with existing, or incrementally enhanced, planners
WSC has much commonality with Planning– Services are Actions
– Side-affects and inputs/ outputs can be modeled as preconditions/ effects
– Use existing or favorite new methods
Many research papers but not many wide-scale systems– Success in generating compositions
– But generation is one thing, execution another• How to prove composition is correct at runtime?• Are middleware available to execute?• Can domain models be built by typical IT professionals?
Anecdote – – Planner4J family of Java planners: Classical, Metric and Contingent planners in three different composition systems
– Never encountered a composition situation where the scalability of the planner was an issue!
– More work on making planner integratable with external systems• Automatic Parameter Turning (AAAI 05)• Analyzing plans (IAAI05)• Validating input domain and problem models (ISWC 2005)• Generating diverse plans (IJCAI 07)• Reachability analysis to identify potentially relevant services from a large repository• See AAAI06 Nectar paper for details
Planner4J: http://domino.research.ibm.com/comm/research_people.nsf/pages/biplav.Planner4J.html
IBM Research
© 2008 IBM Corporation36 The Myth and Reality of Web Services Composition
Reality – Why is WSC not Solved as yet?
Modeling domain is hard– Which expert to believe? Companies in monopolistic situations
(e.g. Windows, SAP) have easier time.
– Can domain models be built by typical IT professionals?
– What is the right level of abstractions?
Handling runtime– How to prove composition is correct at runtime?
– Are middleware available to execute?
Tooling
IBM Research
© 2008 IBM Corporation37 The Myth and Reality of Web Services Composition
Emerging Trends in Resolving WSC Issues
IBM Research
© 2008 IBM Corporation38 The Myth and Reality of Web Services Composition
Business-Process Driven IT
Figure Source: Model-driven Business Process Platforms, David Frankel, SAP
Packaged Middleware: SAP, Oracle, PeopleSoft
Custom-assembly (IBM)
IBM Research
© 2008 IBM Corporation39 The Myth and Reality of Web Services Composition
Business-Process Driven SOA
Business Process
SOA Implementation
(Multiple vendors)
IBM Research
© 2008 IBM Corporation40 The Myth and Reality of Web Services Composition
SAPBPR
IBMReAL
Tagged Content
Content Sources
Specialize
40
Reuse business processes
Reuse services implementing business processes
– Reuse plans representing composite services
Plan Modification and Reuse
IBM Research
© 2008 IBM Corporation41 The Myth and Reality of Web Services Composition
Model-Lite Planning is Planning with incomplete models
..“incomplete” “not enough domain knowledge to verify correctness/optimality”
How incomplete is incomplete?
Missing a couple of preconditions/effects?
Knowing no more than I/O types?
Source: Model-Lite Planning for the Web Age Masses, S. Kambhampati, AAAI07
IBM Research
© 2008 IBM Corporation42 The Myth and Reality of Web Services Composition
Challenges in Realizing Model-Lite Planning
1. Planning support for shallow domain models (Helping human planners)
2. Plan creation with approximate domain models(Planners deal with incompleteness)
3. Learning to improve completeness of domain models (Help complete the model)
Source: Model-Lite Planning for the Web Age Masses, S. Kambhampati, AAAI07
IBM Research
© 2008 IBM Corporation43 The Myth and Reality of Web Services Composition
Conclusion
IT Issues Faced by Businesses Today
Web Services Composition is very important– Model for looking at WSC– Case Studies
Looked at progress in automated WSC– Myth: Resolve scale-up and search issues for WSC composition – Reality: Resolve composition set-up issues (at problem set-up or solving
phases)
Emerging Trends – Plan reuse and modification in the context of richer, but unstructured, domain
models – Planning in the presence of impoverished domain models: model-lite planning
Future Issue: Adaptation
IBM Research
© 2008 IBM Corporation44 The Myth and Reality of Web Services Composition
Additional Material
IBM Research
© 2008 IBM Corporation45 The Myth and Reality of Web Services Composition
Web Services Adaptation
IBM Research
© 2008 IBM Corporation46 The Myth and Reality of Web Services Composition
What Causes the Change (inputs/ events)
Structural
– Component specific events (reconfiguration) e.g. failures
– Temporal specific events e.g. timeouts, unexpected (w.r.t. protocol) messages
Contractual: contract as list of attributes and possible values
– Contract violations or cancellation
– Request for re-negotiation from providers
Non-functional (QoS) parameter changes
– Maintain efficiency or optimality
– Avoid contract violations
Changes in the business environment
– E.g. New laws, business models, personnel changes, technology changes
IBM Research
© 2008 IBM Corporation47 The Myth and Reality of Web Services Composition
What Could the Techniques Change in the Process (outputs/reactions)
Structural
– Spatial/ component: activity/ topology – addition and deletion
– Temporal: change in ordering constraints
Contractual
– Contract as list of attributes and possible values
• Agreement sections: attributes and tolerable values • Separation clauses; re-negotiation clauses
– Differences
• Adaptation: governed by agreement section• Re-negotiation: governed by re-renegotiation section• Separation followed by negotiation: there are be no constraints
– Approach: choose the change provided by the contract and perform
• To what extent can be done automatically?
IBM Research
© 2008 IBM Corporation48 The Myth and Reality of Web Services Composition
A Narrow Mapping from Event Types to Possible Reactions Does Not Exist !!
Default for any event
– Ignore
Marginal QoS Changes
– Ignore
– Re-configuration (using policies)
– Contract cancellation, re-negotiate violating contract, re-adjust other contracts
Contractual cancellation
– Ignore
– Re-configuration (using policies)
– Re-negotiate/ re-adjust violating contract, re-adjust/ cancel other contracts
IBM Research
© 2008 IBM Corporation49 The Myth and Reality of Web Services Composition
Adaptation Techniques
Ignore
Hard-wired ad-hoc changes– Procedural hacks
– Using policies/ rule-based systems/ Event-Condition-Action
Mediation– Ontology-based (semantics)
• Type mapping in Meteor-S– Behavioral
• Controller synthesis (Karsten Wolf’s work)
Re-configuration – Using policies
– Using LP (Benatallah)
– Using Logic (Berardi, ConGolog)
– Graph transformation (Hyperedge replacement - Ugo Montanari)
Negotiation and Re-negotiation – Game theory
Ooops … ask the human!
IBM Research
© 2008 IBM Corporation50 The Myth and Reality of Web Services Composition
Speculation on Complexity of Handling of Events
Trivial[0]
lowhangingfruit [1]
Challenging[3]
Many years away[4]
Impossible[5]
Unknownevents
MarginalQoS differences(A-WSCE)
Ideasexist[2]
Template-based negotiation
New clauses in contract;Renegotiation
Negotiate
Ignoreevents
Structure
Contract
Business
QoS
Contract cancellation
Protocol violationsE.g. controller synthesis
Semantic mediation
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