Ontology-Driven Software Development with Protégé and OWL Holger Knublauch Stanford Medical Informatics Model-Driven Semantic Web Workshop

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

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

Semantic Web Architecture

Ontologies Travel Ontology ActivityProvider ContactAddress Activity AdventureActivity providesActivityhasContact BungeeJumpingCaving HeliBungeeJumping Geography Ontology GeographicArea CountryCity hasLocation Travel Extension Ontologies

Software Architecture (1) Travel.owlCustomer.owl HeliBungee.owl... Semantic Web Layer Internal Layer Ontology representation as Java objects ActivityX.owl Reasoners (OWL DL, SWRL,...) End-User Interface (JSP) Web Service Interface (WSDL) Web Service, Control Logic (Java Code) Core Ontologies

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..* 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..* 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 OntPropertyOntClass RDF Triple Store CustomerActivity Bungee Generic Level Application Level

Software Architecture (2) Travel.owlCustomer.owl HeliBungee.owl... Semantic Web Layer Internal Layer Activity.java... Customer.java... Dynamic Object Model (Jena) ActivityX.owl Reasoners (OWL DL, SWRL,...) End-User Interface (JSP) Web Service Interface (WSDL) Web Service, Control Logic (Java Code) Core Ontologies

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 a new dialect of OO Model ViewControl

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 ViewControl Incremental Code Generation Agile Modeling Agile Programming

Future Work with Protégé (1) Embrace UML, encourage use of OWL Incremental OWL-Java code generation 1.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