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

Agentcommunication,ontologies,protocols,semanticWeb
http://www.lsi.upc.es/~webia/KEMLG
Agent communication, ontologies, protocols,
semantic Web
October 30, 2003
Luigi Ceccaroni, Steven Willmott

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 …

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

Key technology issues in the case of services

Service interaction over a network, and semantics

Service composition

Automated service components
Restaurant
Restaurant
Restaurant
Hotel
Server
Hotel
DF
Barcelona
DF
Paris
ACL
SL
Ontologies

http://www.lsi.upc.es/~webia/KEMLG
Modeling an Agent Service
Platform Deployment
Communication Stack
Design Methodology

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

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

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

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.

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

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

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?)

Descriptions
 Box-Diagram Descriptions

UML-based
n o t - u n d e r s t o o d r e f u s e
r e a s o n
f a ilu re
r e a s o n
in fo rm
D o n e (a c t io n )
in fo rm
( io ta x ( r e s u lt a c t io n ) x )
a g r e e
r e q u e s t
a c t io n

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

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

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

Service Modeling
Recommendations from
Agentcities experience

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

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 UP
1. Have a performative for everything
2. Have very limited content language
 Or push semantics DOWN
1. Use only “request”
2. Define the semantics of every request in the Ontology

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

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

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

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

Agentcities Examples
Evening Organizer Perspective
Travel
Information
Geo
Information
Cinema
Guide
Ratings
Agent
Event Organizer Perspective
Ontology
Ticket
Market Talent
Market
Event
Publicity
Security
Event
Planner
Personal
Agent
Evening
Organiser
Hotel Guide
Restaurant
FinderRestaurant
Guide
Restaurant
Restaurant
Restaurant
Restaurant
Restaurant
Restaurant
Restaurant
Music
Venue
Restaurant
Restaurant
Restaurant
Hotel
Restaurant
Restaurant
Restaurant
Band/
Performer
Restaurant
Restaurant
Restaurant
Cinema
Restaurant
Restaurant
Restaurant
Theatre
Bank
Personal
Agent

Evening Organizer
Personal
Agent
Evening
Organiser
Hotel Guide
Restaurant
Finder
Restaurant
Guide
Restaurant
Restaurant
Restaurant
Restaurant
Restaurant
Restaurant
Restaurant
Music
Venue
Restaurant
Restaurant
Restaurant
Hotel
Restaurant
Restaurant
Restaurant
Band/
Performer
Restaurant
Restaurant
Restaurant
Cinema
Restaurant
Restaurant
Restaurant
Theatre
Travel
Information
Geo
Information
Ratings
Agent
Cinema
Guide
Ticket
Market
Event News

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

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