Jens Lemcke Research Associate, SAP AG Co-Authors: Michael Altenhofen, Egon Börger An Execution...

Jens LemckeResearch Associate, SAP AG

Co-Authors: Michael Altenhofen, Egon Börger

An Execution Semantics for Mediation Patterns

Interaction Mismatches

Outlook

Introduction

Virtual Providers

SAP AG 2005, An Execution Semantics for Mediation Patterns / Jens Lemcke / 4

Introduction and Research Context

WSMO Framework Actors: Business Partners (BP)

Behavioural Interfaces (WSMO: Choreographies)

Interactions of arbitrary BPs

WSMO Process Mediation Mapping Choreographies for Interoperation

Problem: Interaction Mismatches

Solution: Process Mediators (PMs) as transparent connectors


Motivation – Resolvable Interaction Mismatches I

Motivation Informal graphical representation

Ambiguous Interpretations What do two successive links mean? Ordering constraint. What do links mean, and what capitals (A, B)? Links: Messages; Capitals:

Data sets. What connection mode is assumed? Reliable connecions.

Hidden, implicit knowledge

– D13.7, WSMO Deliverable


Motivation – Resolvable Interaction Mismatches II







Motivation – Resolvable Interaction Mismatches III







Motivation – Resolvable Interaction Mismatches IV







Motivation – Resolvable Interaction Mismatches V





Conclusion: A formal representation would be highly appreciable.



Outlook

Introduction

Virtual Providers


Mediators as Virtual Providers (VPs) I

What is the Virtual Provider (VP)? Mediator described by an abstract procedural semantics (given as ASM)

What can be done by using VP? Receive multiple related initial messages

Generate subsequent messages from initial & returned message contents

Receive returned answers

Send answer to initiator


Mediators as Virtual Providers (VPs) II







Mediators as Virtual Providers (VPs) III







Mediators as Virtual Providers (VPs) IV







Mediators as Virtual Providers (VPs) V







Mediation in Virtual Providers (VPs) I

What does the PROCESSing machine do? Working one current request

Controls sending & receiving machines

How can communications be mediated? Incoming messages Create request (from their content)

Compute request by generating a sequence of parallel new requests (msgs)

Generate returning answer


Mediation in Virtual Providers (VPs) II







Mediation in Virtual Providers (VPs) III







Mediation in Virtual Providers (VPs) IV







Outlook

Introduction

Virtual Providers


Refinement of Virtual Provider

Basic Patterns Refine VP

What to do?

Refine data structures

Define:Where to refine? In ReceiveReq


Pattern a) Discard first message

Forward second

Implementation Stateful Block until receipt of second message

Resolvable Interaction Mismatches – Pattern a) I


Pattern a) Discard first message

Forward second


Resolvable Interaction Mismatches – Pattern a) II


Pattern b) Extension to a)

Save both messages

Forward in reverse order


Keep first message in memory

Resolvable Interaction Mismatches – Pattern b) I


Pattern b) Extension to a)

Save both messages

Forward in reverse order


Keep first message in memory

Resolvable Interaction Mismatches – Pattern b) II


Pattern d) Extension to b)

Save both messages

Forward combined message


Keep first message in memory & combine

Resolvable Interaction Mismatches – Pattern d)

Changes over b)


Pattern c) Forward splitted message

Implementation No State Don’t block

Resolvable Interaction Mismatches – Pattern c)


Pattern e) Acknowledge receipt

( Reliable connection implied)

Implementation No State Directly send confirmation

Resolvable Interaction Mismatches – Pattern e)


Outlook

Introduction

Virtual Providers


Mediator Patterns (MPs)

Complex Interaction Patterns VP’s homogeneous Communication structure Chaining VPs

Yields tree-like structure of VP composition:1. A request can be transformed into a sequence of parallel new requests

2. New requests can be handled as in 1 (by a chained VP)

Mediation Component Choose appropriate Mediator Patterns from a library

Mediator Pattern

Virtual Provider


DN, AH, BH

BN

Virtual Internet Service Provider Transparently contacting 3rd parties

via their (different) interfaces

Situation Different interfaces

Solution Library of Mediator Patterns

Mediator Patterns Example – VISP

AN

BN

DN

AH, BH, DH

Req

ues

to

rAN, BN, DN

AH, BH, DH

Pro

vid

er

1

AN

AH

DH

Pro

vid

er

2BH


DN, AH, BH

BN






AN

BN

DN

AH, BH, DH

Req

ues

to

rAN, BN, DN

AH, BH, DH

Pro

vid

er

1

AN

AH

DH

Pro

vid

er

2BH

Library

MP 1

MP 2


DN, AH, BH

BN






AN

BN

DN

AH, BH, DH

Req

ues

to

rAN, BN, DN

AH, BH, DH

Pro

vid

er

1

AN

AH

DH

Pro

vid

er

2BH

Library

MP 1

MP 2

MP 1


DN, AH, BH

BN






AN

BN

DN

AH, BH, DH

Req

ues

to

rAN, BN, DN

AH, BH, DH

Pro

vid

er

1

AN

AH

DH

Pro

vid

er

2BH

Library

MP 1

MP 2

MP 2


Summary and Conclusion

Summary Formal high-level mediator specification

Composition into Mediator Patterns

Representation of interaction mismatches

Using ASM facilitates Unambiguous formal specification

Clear separation of abstraction layers

Identification of refinement spots

Future Work Classification of interaction mismatches

Automated pattern selection / definition

Formalize further components using ASMLike discovery module spec. (Andreas Friesen, Stephan Grimm)

Questions

or Comments ?

Jens Lemcke Research Associate, SAP AG Co-Authors: Michael Altenhofen, Egon Börger An Execution...

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