Slide1 l.jpg
This presentation is the property of its rightful owner.
Sponsored Links
1 / 40

A distributed agent architecture and case-based approach for information system integration PowerPoint PPT Presentation


  • 107 Views
  • Uploaded on
  • Presentation posted in: General

A distributed agent architecture and case-based approach for information system integration. Computer Science Institute University of Ancona. Loris Penserini ([email protected]). In collaboration with:. Maurizio Panti ([email protected]) Luca Spalazzi ([email protected]).

Download Presentation

A distributed agent architecture and case-based approach for information system integration

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Slide1 l.jpg

A distributed agent architectureand case-based approachfor information system integration

Computer Science Institute

University of Ancona

Loris Penserini ([email protected])

In collaboration with:

Maurizio Panti ([email protected])

Luca Spalazzi ([email protected])

(these slides are available at: http://www.cs.toronto.edu/~mkolp/tropos/)

Computer Science Institute - University of Ancona


Slide2 l.jpg

Motivation

In a network environment the principal problems of Information System Integration are:

- distribution: the needing of sharing sources between LANs and/or WANs

- dynamism: new sources can be inserted or deleted, the schemas can be modified and so on

- heterogeneity: discrepancies in physical, logical, and conceptual levels

Computer Science Institute - University of Ancona


Slide3 l.jpg

Work Purpose

- to use an Agent Platform to face the distribution

- to solve dynamic problems by a Distributed CBR approach

- to adopt a Mediator architecture to face the heterogeneity

- to evaluate both the efficacy and the efficiency of the Mediator cooperation strategies by a prototype implementation

Computer Science Institute - University of Ancona


Slide4 l.jpg

* Agent Platform architecture FIPA compliant

* Mediator agent that uses a Distributed CBR

Software

* Mediator prototype and Cooperation Strategies

Case Memory2

Agent

Case Memory1

Mediator1

Mediator2

Wrapper1

Wrapper2

Agent

Management

System

Directory

Facilitator

db1

db2

Agent Communication Channel

Summary

Computer Science Institute - University of Ancona


Slide5 l.jpg

JEAP&FIPA

FIPA Reference Model

Agent Platform (AP) architecture.

AP 1

AP 2

?

?

DF

DF

AMS

AMS

ACC

ACC

Agents

Agents

IIOP

The network

IIOP

IIOP

?

ACC

AMS

DF

Agents

AP 3

Computer Science Institute - University of Ancona


Slide6 l.jpg

JEAP&FIPA

Communication Protocol

FIPA Specification:

FIPA defines two types of communication:

  • Intra-platform

No constraints

  • Inter-platform

Internet Inter-ORB Protocol

CORBA allows several mechanisms in order to locate distribute objects, which are incompatible each other, but FIPA does not specify which one must be used.

Computer Science Institute - University of Ancona


Slide7 l.jpg

JEAP&FIPA

Communication Protocol

AP prototype implementation:

Intra-platform protocol: IIOP

  • IIOP is a well known standard.

  • Code Portability.

  • ACC is simpler.

Computer Science Institute - University of Ancona


Slide8 l.jpg

JEAP&FIPA

Communication Protocol

AP prototype implementation: CORBA mechanisms

  • Interoperable Object Reference (IOR)

  • Transient Name Service (TNS)

Wide compatibility with other FIPA compliant platforms.

Computer Science Institute - University of Ancona


Slide9 l.jpg

JEAP&FIPA

Agent Communication Channel (ACC)

and Agent Management System (AMS)

FIPA Specification:

ACC and AMS strictly interact each other.

ACC supports two kinds of request:

  • implicit ACC request;

  • explicit ACC request (forward action);

Computer Science Institute - University of Ancona


Slide10 l.jpg

JEAP&FIPA

ACC and AMS

Example:

A second source of overload is the task that ACC must do for explicit requests:

(request

:sender [email protected]://192.168.1.1:800/acc

:receiver [email protected]://192.168.1.1:800/acc

:language sl0

:ontology fipa-agent-management

:protocol fipa-request

:content

(action [email protected]://192.168.1.1:800/acc

(forward

(MESSAGE)

))

:reply-with 0)

Computer Science Institute - University of Ancona


Slide11 l.jpg

JEAP&FIPA

ACC and AMS

Agent_i

Agent_j

ACC

AMS

1: request for Agent_j

2: request

3: agree

4: authenticate

5: inform

6: request

from Agent_i

7: agree for

Agent_i

8: request

9: agree

10: authenticate

11: inform

12: agree from Agent_j

13: inform done

for Agent_i

14: request

15: agree

16: authenticate

17: inform

18: inform done from

Agent_j

Computer Science Institute - University of Ancona


Slide12 l.jpg

JEAP&FIPA

ACC and AMS

AP prototype implementation:

ACC and AMS are realised as a single agent:

  • It removes the interaction between ACC and AMS.

  • It does not decrease fault-tolerance capability of the platform.

  • It is still FIPA compliant.

Computer Science Institute - University of Ancona


Slide13 l.jpg

JEAP&FIPA

ACC and AMS

AP prototype implementation:

We only use implicit requests.

  • It reduces the overload for the ACC.

  • It is still FIPA compliant.

Computer Science Institute - University of Ancona


Slide14 l.jpg

JEAP&FIPA

Directory Facilitator (DF)

FIPA Specification:

The DF provides a yellow-pages service.

The agents registered at the DF are classified by means of service-type and service-name.

A Domain is the set of all the agents registered at the DF.

The Agent Universe is the union of all the domains.

Each Agent Platform must have at least one DF (the default DF).

Computer Science Institute - University of Ancona


Slide15 l.jpg

JEAP&FIPA

FIPA Platforms and Domains

Computer Science Institute - University of Ancona


Slide16 l.jpg

JEAP&FIPA

Directory Facilitator (DF)

AP prototype implementation:

Specification are not clear on what default DF can contain and which kind of service-name it must use.

default DF

Service Type Level

FIPA-DF

FIPA–ACC

FIPA – AMS

Service Name Level

Airport

Railway

Agent DF Level (GUID)

DF_i

DF_j

DF_k

Logic structure of the default DF.

Computer Science Institute - University of Ancona


Slide17 l.jpg

JEAP&FIPA

Agent Platform

1:Search for a domain

Agent_i

DF Default

2:Answer with DF_j address

3:Search for an agent

5:Invoke the service

6:Results

4:Answer with agent address (Agent_k)

DF_j

Agent_k

Directory Facilitator (DF)

AP prototype implementation: example

A possible situation in which Agent_i would like to use a service that can perform the Wrapper_i, but at the begin Agent_i doesn’t know that.

Computer Science Institute - University of Ancona


Slide18 l.jpg

JEAP&FIPA

Some Remarks on FIPA

FIPA is an effective solution to agent cooperation in heterogeneous and distributed environments.

Nevertheless FIPA specification are not clear:

  • Communication protocols: intra-platform and inter-platform;

  • ACC and AMS: they have a strictly interaction and ACC is overburdened by the forward action;

  • Default DF: its role and organisation are not clear.

Computer Science Institute - University of Ancona


Slide19 l.jpg

DCBR approach

Project Overview

Computer Science Institute - University of Ancona


Slide20 l.jpg

CBR approach

Query Representation: Case Memory

Example:

Computer Science Institute - University of Ancona


Slide21 l.jpg

CBR approach

Local Query Rewriting: Terminology

The problems (queries, Q) are classifies according to subsumption relation.

In particularly, in this work, Q is decomposed and then classified.

For example:

Computer Science Institute - University of Ancona


Slide22 l.jpg

CBR approach

Local Query Rewriting

Query Evaluation: the Mediator sends a decomposition of Q to the related information source and wait for their answers.

Local Failure in Query Reuse: the Mediator is not able to rewrite Q since its case memory contains no past cases that can be used to do it. For example, it is the first time that the consumer formulates such a query, i.e., the consumer has a new information need.

Local Failure in Query Evaluation: the Mediator sends a rewritten query to related sources and receives at least an empty answer. This means that the case memory of the mediator is not updated (an information source has been removed from system or changed its schema).

Computer Science Institute - University of Ancona


Slide23 l.jpg

DCBR approach

Distributed Query Rewriting

Principal Cooperation Strategies:

Partners

Queries

Answers

Mediators

Sources

Original

Rewritten

Rewritten

Data

all, the newer, the older, ...

the whole query, its components, ...

Computer Science Institute - University of Ancona


Slide24 l.jpg

DCBR approach

Distributed Query Rewriting

A first strategy: the Mediator cooperates with other mediators, send them the original query, and asks for receiving the rewritten query.

First consideration

Theorem. Let M, N be two mediators such that M interacts with N when M fails. Let Cn(M) be the case memory of M after n interactions with N. Let Cn(N) be the case memory of N such that it does not change while N interacts with M. Then

redundancy

Computer Science Institute - University of Ancona


Slide25 l.jpg

DCBR approach

Distributed Query Rewriting

A first strategy: the Mediator cooperates with other mediators, send them the original query, and asks for receiving the rewritten query.

Second consideration

Theorem. Let be n information sources. Let V be a view of . Let M, N be two mediators such that M interacts with N when M fails. Let Cn(M) be the mediated schema of M after n interactions with N. Then

Computer Science Institute - University of Ancona


Slide26 l.jpg

DCBR approach

Distributed Query Rewriting

A second strategy: the Mediator cooperates with information sources, sends them the original query, and receives the rewritten query.

Theorem. Let be n information sources. Let V be a view of . V is represented as a case memory that does not change. Let M be a Mediator such that M interacts with when it fails. Let Cn(M) be the case memory of M after n interactions with . Then

Computer Science Institute - University of Ancona


Slide27 l.jpg

DCBR approach

Some Considerations

Notation

Sol (Q) :

the solution of Q (problem) respect the source S --> rewritten

I (Sol (Q)) :

the interpretation of the solution of Q both respect the source S --> data

S

S

S

Computer Science Institute - University of Ancona


Slide28 l.jpg

Mediator Prototype

Mediator Prototype

- Its language is a restrict set of Sequel Query Language

- It implements a wide set of cooperation strategies

- It collaborates with other mediators and ‘simple’ wrappers

- Its Solution-Analysing and the Case-Memory Updating phases are still user driven

Computer Science Institute - University of Ancona


Slide29 l.jpg

Mediator Prototype

PROB:select EmployeeInfo from Employee

SOL:"select EmployeeName from [email protected]@ iiop:// 129.100.27.30:900/acc" and "select EmployeeAddr from [email protected]@iiop://193.205.128.40:1000/acc"

Case Memory Organization

Computer Science Institute - University of Ancona


Slide30 l.jpg

Mediator Prototype

Failure in Retrieval

Different cases of failure during retrieval:

- in reuse

- in evaluation (partial or total)

- by the user feedback

Computer Science Institute - University of Ancona


Slide31 l.jpg

Mediator Prototype

Session Example

failure in reuse

Agent i

Mediator

Wrapper 1

Wrapper 2

1: solution requests

to mediator

2: It checks in its knowledge

ð

OK

Wrapper interrogation

3.1: request to wrapper 1

solve

4.1:

3.2: request to wrapper 1

solve

4.2:

3.3: request to wrapper 2

4.3: solve

5.1: data

partial failure in evaluation

5.2: failure

5.3: data

6: Case Memory update

7.1: data

user feedback

7.2: failure

7.3: data

Computer Science Institute - University of Ancona


Slide32 l.jpg

Mediator Prototype

select EmployeeInfo from Employee

Cooperation Strategies

Computer Science Institute - University of Ancona


Slide33 l.jpg

Mediator Prototype

1: request

Mediator 1

Mediator 2

2: rewrite

3: data

2: data

3: data

W1

W2

W3

Cooperation Example

Computer Science Institute - University of Ancona


Slide34 l.jpg

Mediator Prototype

Strategies Evaluation

The tests have evaluated, for each strategy, these kinds of problems :

- knowledge growing

- knowledge redundancy

- response time

- network overload

Computer Science Institute - University of Ancona


Slide35 l.jpg

Mediator Prototype

Strategies Evaluation

The principals tests consist in five general queries (problems) all performed on the following five different strategies:

Strategy 1: a mediator (M) sends the original query (Q) to another mediator (N) and requests for a rewrite

Strategy 2: M sends a decomposition of Q to N and requests for a rewrite

Strategy 3: M sends to N only the rewrited components of Q that it cannot solve and asks for the data

Strategy 4: M directly sends a decomposition of Q to the wrappers and asks them for the data

Strategy 5: M directly sends only the rewrited components of Q to the wrappers and asks for the data

Computer Science Institute - University of Ancona


Slide36 l.jpg

Mediator Prototype

Strategies Evaluation: Results

Computer Science Institute - University of Ancona


Slide37 l.jpg

Mediator Prototype

Strategies Evaluation: Results

Computer Science Institute - University of Ancona


Slide38 l.jpg

Mediator Prototype

Strategies Evaluation: Results

Steps: principal phases of a communication (without any FIPA protocols)

Service Messages: they do not contain data (query responses) inside otherwise they should be considered ‘Data Messages’

Small/Big Messages: it is another possible type of messages subdivision based on the content of a FIPA message (e.g. an ‘agree’ message is considered ‘small’, whereas an ‘inform’ messages is big, and so on)

Computer Science Institute - University of Ancona


Slide39 l.jpg

Future Development

- The designing and developing of a Mediator agent that uses a CBR engine based on DL

- The designing of protocols that automatically choice the best strategy in response to a particular failure

- To consider other useful cooperation strategies

- To apply this architecture in a real case of interest to test its capacity (e.g. some kind of web applications)

Computer Science Institute - University of Ancona


Slide40 l.jpg

References

- M. Panti, L. Penserini, L. Spalazzi, S. Valenti, "A FIPA Compliant Agent Platform for Federated Information Systems", International Journal of Computer & Information Science, R. Y. Lee and H. Fouchal (eds), ACIS, 2000.

- C. Cioffi, M. Panti, L. Penserini, L. Spalazzi, E. Tonucci, S. Valenti, ``An Agent-Based Platform for Federated Information Systems: Some Design Issues'', in Proc. of the International Conference on Software Engineering Applied to Networking and Parallel/Distributed Computing (SNPD '00), Reims, France, May 18-21, 2000.

- M. Panti, L. Penserini, L. Spalazzi, ``A Critical Discussion about an Agent Platform based on FIPA Specification'', in Atti dell'Ottavo Convegno Nazionale su Sistemi Evoluti per Basi di Dati (SEBD 2000), L'Aquila Italia, 26-28 Giugno 2000.

- M. Panti, L. Spalazzi, A. Giretti, “A case-based approach to information integration”, In Proceedings of the 26th International Conference on Very Large Databases, Cairo, Egypt, 10–14 September 2000.

- Foundation for Intelligent Physical Agents, Fipa 2000 Specification. Geneva, Switzerland, October 2000. Available at: http://www.fipa.org/

- E. Plaza, J. L. Arcos, and F. Martìn, “Cooperative Case-Based Reasoning”, In G. Weiss, editor, Distributed Artificial Intelligence meets Machine Learning, Lecture Notes in Artificial Intelligence, Berlin, 1997. Springer Verlag.

- G. Wiederhold, “Mediators in the architectures of future information systems”, in IEEE Computer, vol. 25, N. 3, pp. 38--49, 1992.

Computer Science Institute - University of Ancona


  • Login