The Myth and Reality of (Automated) Web Services Composition

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Oct 30, 2013 (3 years and 11 months ago)

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IBM Research

© 2008 IBM Corporation

The Myth and Reality of

(Automated) Web Services Composition


Dr. Biplav Srivastava

http://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, Athens

ASU: April 2008

IBM Research

© 2008 IBM Corporation

2

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 Corporation

3

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 Corporation

4

The Myth and Reality of Web Services Composition

Background: Web Services

Service
Broker

Service
Provider


Service
Requester

WSDL

Search 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 Corporation

5

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 Corporation

6

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 Corporation

7

The Myth and Reality of Web Services Composition

Case Study: Application Integration

IBM Research

© 2008 IBM Corporation

8

The Myth and Reality of Web Services Composition

Telco Ecosystem


Service/content providers are often 3
rd

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


3
rd

Party

Providers

Telco

Enterprise

User

User

User

IBM Research

© 2008 IBM Corporation

9

The Myth and Reality of Web Services Composition

Composed Service: Helpline Automation

Problem

Reporting

Registry

Update

Call

Setup

Help Desk

Message

Delivery

On Site

Problem

Classification

Location
-
based

Agent Selection

Expert Lookup

Agent Assignment

Desk
-
based Expert ID

Field Expert ID

Problem Ticket

Problem Ticket,

Problem Ticket,

Resolution Status

Problem Ticket,

Resolution Status

Problem 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 Corporation

10

The Myth and Reality of Web Services Composition

Creation of a new service


Main Issues


Scalability of composition solution


Level of automation


Modeling domain information


Leverage industry practices

Specify end
-
user
service capability

Select service
providers

Design the

flow

Deploy the

service

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 Corporation

11

The Myth and Reality of Web Services Composition

Synthy System Architecture

Abstract
Workflow

(Plan)

Domain
Ontology

Service
Registry

Deployable

Workflow

Service

Specification

Logical

Composer

Physical

Composer

Execution Environment

Service Creation

Environment


Key Components


Service Capabilities Database


Information about services available
in
-
house as well as with 3
rd

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/bipl av.Synthy.html

IBM Research

© 2008 IBM Corporation

12

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 Engineer

Service Developer

Web

Service

Rqmt.

Service

Discovery

Service

Selection

Service

Aggregation

Service

Deploy
-

-
ment

Composite

Service

OWL
-
S,

WSDL

BPEL

BPEL

OWL
-
S

IBM Research

© 2008 IBM Corporation

13

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 Corporation

14

The Myth and Reality of Web Services Composition

Case Study: Online Data Aggregation

IBM Research

© 2008 IBM Corporation

15

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,

IA
AI 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 Corporation

16

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,

IA
AI 2002

IBM Research

© 2008 IBM Corporation

17

The Myth and Reality of Web Services Composition

Case Study: Mashup Advisor

IBM Research

© 2008 IBM Corporation

18

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 Goodwin

Extended Team: Biplav Srivastava

IBM Research

© 2008 IBM Corporation

19

The Myth and Reality of Web Services Composition

System Architecture

MashupA

Repository Manager

Catalogue

Manager

Mashup
Repository

Domain
Ontology

Statistics

Manager

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 Corporation

20

The Myth and Reality of Web Services Composition

A Framework for Understanding WSCE

IBM Research

© 2008 IBM Corporation

21

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 Service

Composition and

Execution

Specification

of Requirement

Available

Capabilities

[ Templates,


Policies ]

Execution

Trace


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 Corporation

22

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 Corporation

23

The Myth and Reality of Web Services Composition

Search
-
based

Composition


Execution

Specifications

X={x
1
,x
2
,…x

}

T=

{t
1
,t
2
,…t

}

Interleaved Approach

On
-
line

Events

Example:
ConGolog, Heracles+Theseus


IBM Research

© 2008 IBM Corporation

24

The Myth and Reality of Web Services Composition

Monolithic

Composition

Runtime

Specifications

I={i
1
, i
2
,… i

}

X={x
1
,x
2
,…x

}

W={W
1
,W
2
,…W
L
}

T=

{t
1
,t
2
,…t

}

F
RE

R
IW

R
EW

Monolithic Approach

Off
-
line

On
-
line

Events






Example:
SWORD, SHOP
-
2 based, Petrinet
-
based, Astro, METEOR
-
S


IBM Research

© 2008 IBM Corporation

25

The Myth and Reality of Web Services Composition

Logical

Composition

Physical

Composition

Runtime

Specifications

C={c
1
,c
2
,…c

}

I={i
1
, i
2
,… i

}

S={S
1
,S
2
,…S
K
}

W={W
1
,W
2
,…W
L
}

T=

{t
1
,t
2
,…t

}

F
PC

F
RE

R
AW

R
IW

R
EW

Staged Approach

Off
-
line

On
-
line

Off
-
line

X={x
1
,x
2
,…x

}

Events










Example:
Synthy, Self
-
Serv with web communities (but informal modeling)


IBM Research

© 2008 IBM Corporation

26

The Myth and Reality of Web Services Composition

Template
-
based Approach: Creation of a Template

T= {t
1
,t
2
,…t

}

W={W
1
,W
2
,…W
L
}

S={S
1
,S
2
,…S
K
}

Generalize
:
remove commitments to get templates

Templates

Staged

Monolithic

Interleaved

Traces

Executable Workflow

Abstract Workflow

IBM Research

© 2008 IBM Corporation

27

The Myth and Reality of Web Services Composition

Usage of a Template

T= {t
1
,t
2
,…t

}

Templates

W={W
1
,W
2
,…W
L
}

S={S
1
,S
2
,…S
K
}

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 Corporation

28

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 Corporation

29

The Myth and Reality of Web Services Composition

Comparing Approaches

Interleaved

Monolithic

Staged

Template

Composition
Effort

O(

λ
)

O(
β
λ
)

Min: O(

λ
)

O(
α
λ

+ M
λ
)

O(M
λ
)

Composition
Control

None

Low:

< R
IW
; F
E

>

High:

< R
AW
;R
IW
; F
C
; F
E

>

High:

<template, underlying
composition method>

Ability to Handle
Composition
Failure

None

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)

Limitation

Search 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 Corporation

30

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 Corporation

31

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(
β
λ
)

Min: O(

λ
)

O(
α
λ

+ M
λ
)

O(M
λ
)

Composition Control

None

Low:

< R
IW
; F
E

>

High:

< R
AW
;R
IW
; F
C
; F
E

>

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)

Limitation

Search 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 Corporation

32

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(
β
λ
)

Min: O(

λ
)

O(
α
λ

+ M
λ
)

O(M
λ
)

Composition Control

None

Low:

< R
IW
; F
E

>

High:

< R
AW
;R
IW
; F
C
; F
E

>

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)

Limitation

Search 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 Corporation

33

The Myth and Reality of Web Services Composition

An Update on Progress in Automated WSC

IBM Research

© 2008 IBM Corporation

34

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 Corporation

35

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/bipl av.Planner4J.html

IBM Research

© 2008 IBM Corporation

36

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 Corporation

37

The Myth and Reality of Web Services Composition

Emerging Trends in Resolving WSC Issues

IBM Research

© 2008 IBM Corporation

38

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 Corporation

39

The Myth and Reality of Web Services Composition

Business
-
Process Driven SOA

Business Process

SOA Implementation

(Multiple vendors)

IBM Research

© 2008 IBM Corporation

40

The Myth and Reality of Web Services Composition

SAP

BPR

IBM

ReAL

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 Corporation

41

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 Corporation

42

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 Corporation

43

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 Corporation

44

The Myth and Reality of Web Services Composition

Additional Material

IBM Research

© 2008 IBM Corporation

45

The Myth and Reality of Web Services Composition

Web Services Adaptation

IBM Research

© 2008 IBM Corporation

46

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 Corporation

47

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 Corporation

48

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 Corporation

49

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 Corporation

50

The Myth and Reality of Web Services Composition

Speculation on Complexity of Handling of Events

Trivial

[0]

low

hanging

fruit [1]

Challenging

[3]

Many years

away

[4]

Impossible

[5]

Unknown

events

Marginal

QoS differences

(A
-
WSCE)

Ideas

exist

[2]


Template
-
based

negotiation

New clauses in

contract;

Renegotiation

Negotiate

Ignore

events

Structure

Contract

Business

QoS


Contract

cancellation


Protocol violations

E.g. controller synthesis

Semantic mediation