KNOWLEDGE REPRESENTATION

Ontologies

Communication – Network Management Technologies

Rashid Mijumbi

Barcelona, April 2011

Data and Information ModelsDefinition

A model is a representation of the entities in a managed

environment.

Provides a common terminology for representing management

information, relationships, constraints, rules, and operations to specify data

syntax for a chosen domain of discourse

DM 1 DM 3

IM 1

DM 2

Conceptual/Abstract

model for designers and

operators – High Level

Representation

Concrete model (for

implementors) – Low

Level Representation –

More Details

Data Models (1)The “Necessary Evil”

IPsec VPN MPLS VPN MPLS – TE MPLS – QoS

Specific Device Model

Specific Device Model

Specific Device Model

Specific Device Model

Specific Device #1

Specific Device #2

Specific Device #3

Specific Device #4

Tra

nsla

tion

La

yer

N Different Technologies

Atleast N*M translations

needed

M Devices

Heterogeneity in systems makes different Data Models a necessity

Data Models (2)Problems

Data harmonisation problem in Data Models

Billing ApplicationCustomer Name: rashid.mijumbi

Fault Management Application

Customer Name: mrashid

Security ApplicationCustomer Name: rmijumbi

Information Models (1)Abstraction, Data Harmonised (no Conflicts)

Information Model

Standards – Based Data Model

Vendor – Based Data Model

1 : N

1 : M

Information Models (2)Router Configuration Example

CISCO

Juniper

Router(config)# router bgp autonomous-system

Router(config-router)# neighbor

{ ip-address | peer-group-name} remote-as number

Router(config-router)# neighbor ip-address activate

routing-instances { routing-instance-name {

protocols { bgp {

group group-name; { peer-as as-number;

neighbor ip-address; } } } } }

- Different Languages

- Different Semantics

- Different programming models

DEFINING BGP PEERS

Ontologies (1)

Ontologies (2) Ontology refers to the shared understanding of some domain of

interest which may be used as a unifying framework – Uschold and

Gruininger (1996)

An ontology is an explicit specification of a conceptualisation. – Gruber

1993

Ontologies offer a formal mechanism for defining an understanding of

data

Ontological Commitments

Ontology Requirements: Clarity, Coherence, Extensibility, Minimal

encoding bias, Minimal ontological commitment

Ontology Languages An ontology language is made up of three components

syntax, semantics (model theory), proof theory.

The syntax of an ontology language is itself divided into three areas

Logic lexicon, non-logic lexicon and Grammar. By Syntax

CycL and KIF are examples of languages that support expressions in first-order logic.

By Structure These languages use a markup scheme to encode knowledge,

most commonly XML. Ontology Inference Layer (OIL), OWL.

Ontology Tools Ontology development tools

Ontology development tools

can be further distinguished

as: those that are independent

of an ontology language, and

those that are tightly

dependent on one.

Protégé, Ontolingua.

Ontology merging tools

PROMPT, Chimaera.

Semantic Web (1)

User lives in Barcelona and

wants to buy a car locally. He

can afford up to £500. He

wants a red car.

<car><location>Hospitalet</location><price>€400</price><colour>maroon</colour><description>Old banger</description><model>Ford Escort</model>

</car>

UsedCars WebsiteUser

A new form of web content that is meaningful to computers - Berners-Lee 2001

This is because computers cannot process

the semantics that are associated with

web content

Semantic Web (2)

Ontologies:• Define relationships:

relationship between, say, a postcode, a town, a suburb, etc

Mapping Service

User

Wordnet

Ford New Cars

BCN Cars

UsedCars Website