@lis agent communication, ontologies, protocols, semantic web 2003

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http://www.lsi.upc.es/~webia/KEMLG

Agent communication, ontologies, protocols, semantic Web

October 30, 2003

Luigi Ceccaroni, Steven Willmott

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Problem

While there are all sorts of useful databases, services and modeling packages being developed by companies and universities, they all exist in isolated developmental bubbles. Each such tool expects the world to conform to its requirements. Since the tools are so valuable, the world will do exactly that, but …

… we expect to see vast resources applied to the problem of getting data from one bubble into another.

There is a fractured mess of data, services and modeling fiefdoms (feudos). The medium for data transfer will continue to be sleep-deprived individual human researchers until …

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Solution

… the time when we know how to make software that is good at bridging bubbles on its own.

Ontologies are the semantic foundation of this software.

Intelligent agents are the autonomous components of this software

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Key technology issues in the case of services

Service interaction over a network, and semantics Service composition Automated service components

RestaurantRestaurantRestaurant

HotelServer

Hotel

DFBarcelona

DFParis

ACLSL

Ontologies

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http://www.lsi.upc.es/~webia/KEMLG

Modeling an Agent Service

Platform Deployment

Communication Stack

Design Methodology

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Deploying an agent Platform

Machine Any operating system Outside the firewall (or with necessary access) Permanent connection if possible

FIPA Compliant Agent Platform “Roll your own” Use one of the 20 or so available, better if it’s JADE

Install and Deploy the Platform External Address

Register the platform Create a group on [http://www.agentcities.net] Register you platform data (address, name, …) Activate the monitoring services

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Communication Stack among agents

Level Description Example

Conversation Sequence of communicative acts related to a particular topic

Communicating about buying and eating an apple

Communicative Act

Communication about a piece of content

Requesting somebody to perform the action of eating an apple

Content Expression

Description of states of the world over objects

Expressing the action of eating an apple

Ontology Description of objects in the domain

Meaning of apple and eat

Syntax Representation of Content HTML, JPG, SQL

Protocol Data exchange protocol HTTP, GIIOP, SMTP

Transport Physical transport and low level transport protocols

Optical Fiber, TCP-IP

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Design Methodology for services

Service Specification What functionality do we want? What agents do we

need?

Design Protocols: map into interaction sequences Performatives (e.g.: ask, tell, advertise): find out which

ones you need Content Expressions: work out what content is needed Ontology: build a domain model

Top-down design recommended Bottom-up design might also be valid for very generic

services

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Need for Ontologies: a definition

Ontology, or semantic mapping, is the base of semantic processing. An ontology is a network of concepts, relationships and axioms to represent, organize, understand a domain of knowledge relevant to an organization. An ontology provides the common frame of reference for all applications in the environment. An ontology defines the applications’ domain and its boundaries.

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Need for Ontologies: requirements

The meaning of the things referred to in the domain (Vocabulary)

To know what possible values exist (Vocabulary) To know about underlying relationships among items

(Conceptualization) To know how to make inferences (Axioms) To effectively interpret return values and parameter

values

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Other needs

Structured Content Expression Content Languages structure content communication

Performatives Two models:

• One communication act with semantics Do this: easily understood but very general

• A complex infinity of communication acts: user defined and often with no semantics defined

Method calls (actions) • Performatives pick a fixed action set with well defined and

agreed semantics, and a broad coverage of most applications

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Other needs

Interaction Protocols String together several communicative acts (interactions)

into a useful sequence, with coherent aim and semantic description

In general we require• Extended Interactions with multiple steps• Asynchronous Interactions• Link with Semantics (what does a certain sequence mean in

total?)

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Descriptions

Box-Diagram Descriptions UML-based

no t-unders tood re fusereason

fa i lu rereason

in fo rmD one(ac t ion)

in fo rm(io ta x ( resu lt act ion) x)

ag ree

requestac t ion

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Information Exchange, SL, ontologies

Agent Communication uses: asynchronous message passing SL as content language

Terminals in SL often bottom out into: Strings Numerical constants (these need to be replaced by things in the ontology)

Example ((action (agent-identifier :name X)

(read-book :title “Fundamentals of SQL”

:author …) ) )

FIPA Agent Management Ontology

Domain Ontology

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Frame Representation

Frame

Ontology

agent-identifier

FIPA-Agent-Management

Parameter Description Presence Type

name The symbolic name of the agent.

Mandatory Word

addresses A sequence of ordered transport addresses where the agent can be contacted. The order implies a preference relation of the agent to receive messages over that address.

Optional Sequence of URL

resolvers A sequence of ordered AIDs where name resolution services for the agent can be contacted. The order in the sequence implies a preference in the list of resolvers.

Optional Sequence of agent-identifier

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Agent-identifier

Example

(agent-identifier :name Arnold.Schwarzenegger :addresses (sequence http://www.governor.ca.gov, …):resolvers (sequence (agent-identifier :name Hollywood.LA, …)

)

- Green underlined items are named in the ontology- Orange italic items are values (may or may not be in the

ontology)- Black items part of SL syntax

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Service Modeling

Recommendations from

Agentcities experience

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Distribute Complexity over Layers

(query-ref :sender …i :receiver …j :content (iota ?x (is_car

:color red:make

ford )

))

(request :sender …i :receiver …j :content (action j

(send-information(iota ?x (is_car

:color red:make

ford )

)))Could be defined in any

way the programmer likes

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Distribute Complexity over Layers

The two versions are potentially equivalent In the right hand version, semantics is redefined in the

ontology We could have a performative for everything or put

everything in the ontology

We could push semantics UP1. Have a performative for everything 2. Have very limited content language

Or push semantics DOWN1. Use only “request”2. Define the semantics of every request in the Ontology

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Focus on Application Characteristics

What is happening at the application level? Try to abstract away implementation details

Make ontologies generic Concentrate on general descriptions of the world which

feed into your application This leads to greater re-use

Focus on the goals of the interactions between your agents

Not on the details of how your particular mechanism works

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Use Real Data Sources

The Web is full of information Ontologies and service models exist for many domains When working in a domain, identify the industry

standards body or group which guide consensus

Data sources International and business organizations Domain leading web sites ebXML, BizTalk, UDDI, Jini community -> all producing

and storing XML based examples Dublin core

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Work Top-Down

It keeps you focused on your application Try to restrict your view (the generally intelligent agent is

a while away…) Build simple models first Select the correct granularity (is a hotel an agent or

should it be a hotel chain?) Match the real world in granularity (hotels are

independent but don’t often have their own websites)

Smaller granularity More work More potential re-use in other services

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Be Rigorous

Formal models are important and useless if they are not adhered to

Formal models are almost never adequate If you need to deviate from them

• Do so in a principled way • Document how and why you deviated• Feed them back to the community

Be rigorous in your descriptions Precise specifications Formal grammars Correct use of the agreed semantics

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Agentcities ExamplesEvening Organizer Perspective

TravelInformation

GeoInformation

CinemaGuide

RatingsAgent

Event Organizer Perspective

Ontology

TicketMarket Talent

Market

EventPublicity

Security

EventPlanner

PersonalAgent

EveningOrganiser

Hotel Guide

RestaurantFinderRestaurant

Guide

RestaurantRestaurantRestaurantRestaurant


MusicVenue


Hotel


Band/Performer


Cinema


Theatre

Bank

PersonalAgent

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Evening Organizer

PersonalAgent

EveningOrganiser

Hotel Guide

RestaurantFinder

RestaurantGuide

RestaurantRestaurantRestaurantRestaurant


MusicVenue


Hotel


Band/Performer


Cinema


Theatre

TravelInformation

GeoInformation

RatingsAgent

CinemaGuide

TicketMarket

Event News

Documents

@lis agent communication, ontologies, protocols, semantic web 2003