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Ontology-Driven Software Development with Protégé and OWL
Holger KnublauchStanford Medical Informatics
Model-Driven Semantic Web Workshop21.09.2004
Protégé
Core System (since 1990s)
• Generic metamodel (OKBC)• Configurable• Open platform with “Plugins”
OWL Plugin (since 2003)
• OWL Full metamodel• Optimized user interface• Built-in reasoning access • Several thousand users
Protégé / OWL Plugin
Protégé / OWL Plugin
Overview
• How to develop Semantic Web applications?– Example– Architecture and OWL-Java mapping– Tool support
• Can we apply this to general purpose MDA?– OWL is often more suitable than UML– Major benefit: Semantics at edit-time & run-time
Example Scenario
Traditional Web Architecture
Travel PlanningPortal
Database
AccommodationPortal
Database
Cruise Operator
Boat Rental
Hotel
Submission Forms Query Interfaces
End User
Manual actionsAutomated actions
Semantic Web Architecture
Cruise Operator
Boat Rental
Hotel
Service Metadata
End User
OWL
OWL
OWL
CrawlerAgent
Travel ServicesDatabaseand Agent
OWL
User Profile
Query Interface
Manual actionsAutomated actions
Web
Ser
vice
OntologiesTravel Ontology
ActivityProvider
ContactAddressActivity
AdventureActivity
providesActivity hasContact
BungeeJumping Caving
HeliBungeeJumping
Geography Ontology
GeographicArea
CountryCity
hasLocation
Travel Extension Ontologies
Software Architecture (1)
Travel.owl Customer.owl
HeliBungee.owl ...
Sem
antic
Web
Lay
erIn
tern
al L
ayer
Ontology representationas Java objects
ActivityX.owl
Reasoners (OWL DL, SWRL, ...)
End-UserInterface
(JSP)
Web ServiceInterface(WSDL)
Web Service, Control Logic(Java Code)
Cor
e O
ntol
ogie
s
Ontology Code in Java
OntModel model = ...;OntProperty nameProperty = model.getOntProperty(baseURI + “name”);Individual myActivity = model.getIndividual(baseURI + “test”);String name = myActivity.getPropertyValue(nameProperty);Bookings.book(myActivity);...
XYModel model = ...;Activity myActivity = model.getActivity(baseURI + “test”);String name = myActivity.getName();myActivity.book();...
Typical approach with a generic API (Jena):
Nicer approach with a customized API:
UML to Java (conventional)
Activity
- name : String
ActivityProvider
providedBy
0..*
0..*
public class Activity {
private String name;
private Collection providers;
public String getName()
public void setName(String name)
public Iterator listProviders()
public void addProvider(ActivityProvider p)
public void removeProvider(ActivityProvider p)}
OWL to Java (Jena)
Activity
- name : String
ActivityProvider
providedBy
0..*
0..*
public class Activity extends OntClassImpl {
public String getName()
public void setName(String name)
public Iterator listProviders()
public void addProvider(ActivityProvider p)
public void removeProvider(ActivityProvider p)}
Working with Jena Classes
Resource
OntProperty OntClass
RDFTriple Store
Customer Activity
Bungee
Generic Level
Application Level
Software Architecture (2)
Travel.owl Customer.owl
HeliBungee.owl ...
Sem
antic
Web
Lay
erIn
tern
al L
ayer
Activity.java...
Customer.java...
Dynamic Object Model (Jena)
ActivityX.owl
Reasoners (OWL DL, SWRL, ...)
End-UserInterface
(JSP)
Web ServiceInterface(WSDL)
Web Service, Control Logic(Java Code)
Cor
e O
ntol
ogie
s
Dynamic Object Model• Model is accessible at run-time:
– Generic algorithms/reasoners can be executed– Generic test cases available at run-time– Generic serialization, database storage etc.– Generic user interfaces can be generated– Classes can be handled as individuals
(Metaclasses are supported)– Instances can have multiple types
(dynamic polymorphism using Jena API)– Instances can be classified & change types
Other OWL to Java Benefits
Traditional Code:
Code based on generated Jena classes:
Collection patients = model.getPatients();for(Iterator it = patients.iterator(); it.hasNext(); ) { Patient patient = (Patient) it.next(); if(patient.isMale()) { patient.doSomething(); }}
for(Iterator it = model.listIndividuals(MALE, true); it.hasNext(); ) { Patient patient = (Patient) it.next(); patient.doSomething();}
Generalizing This Approach
• Every program has a “domain model”– Customers, Accounts, Products– Patients, Diseases, Treatments
• Domain model is potentially most reusable
• No real need for UML
• Paradigm shift to anew dialect of OO
Model
View Control
Dynamic Object Models and MDA
• MDA taken to extremes
• Design not only to generate code
• Design is part of the deployed system– Open ontologies to share between applications– Machine-accessible semantics at run-time– Built-in reflection across metalevels
• However: Limited expressivity of OWL; Coding needed (procedural attachment).
Advantages of OWL over UML
• Explicit, sharable modeling artifacts
• Open architecture of Semantic Web
• OWL has rich semantics– closer to domain than UML– built-in reasoning support (DL, SWRL)
• A single language across metalevels
Strengths of tools like Protégé
• Can be used by domain experts
• Better scalable than visual UML modeling
• Reasoning support at edit-time
• Rapid prototyping of models
• Individuals can be acquired using forms
• Open architecture / adaptability
• Start your application as a plugin
Ontology-Driven Development
Model
View ControlIncrem
ental Code
Generation
Agile Modeling
Agile Programming
Future Work with Protégé (1)
• Embrace UML, encourage use of OWL
• Incremental OWL-Java code generation1. Determine optimal mapping OWL to Java,
(using an example application)
2. Define rules for updating code in response to changes in the ontology (create, rename, etc).
3. Write Eclipse plugin to perform the updating (either directly or in batch mode)
Future Work with Protégé (2)
• Use Protégé as an ODM editor
• Map core Protégé metamodel to RDF(S)
Collaborations?
ODM Bridge