TOOL PRESENTATION?: Rule languages and inference engines incorporate reasoning capabilities to Web information systems. This demonstration paper presents a tool for the development of rulebased applications for the Web based on OWL and SWRL ontologies. The tool applies a model-driven approach to an ontology representing a domain conceptualization and inference model of the problem domain. It automatically generates a rich, functional Web architecture based on the Model-View-Control architectural pattern and the JavaServer Faces technology, embedding a Jess rule engine for reasoning and deriving new information.
been presented, the TwoUse Toolkit 3 [
This demo presents a tool which provides a model-driven approach to develop rule-based Web applications based on OWL and SWRL models created with TwoUse. The tool applies MDD to produce the implementation of a functional, rich Web architecture which embeds the Jess rule engine for inferencing tasks. The functionality for the generated rule-based Web application is prede ned to enable end-users to create, retrieve, update and delete instances (CRUD). In contrast to current tools for automatic generation of CRUD systems that perform those functions on relational databases, our contribution is that this functionality is executed on the rule engine working memory, enabling the execution of a forward-chaining inference mechanism to drive the reasoning process.
This paper is organized as follows: Section 2 introduces the model-driven approach applied in the tool. Next, Section 3 describes the architecture for the rule-based Web application generated. Finally, the main conclusions and future work are summarized. 2
Model-driven process implemented in the tool The proposed tool uses OWL and SWRL ontologies created with TwoUse as source models for the model-driven approach. We focus on OWL DL sublanguage of OWL. Classes, properties, and individuals de ne the structure of data, whereas rules describe logical dependencies between the elements of the ontology refereed in the rule's antecedent and consequent.
Figure 1 shows a simpli ed schema of the MDD process implemented in the
proposed tool. Two di erent results are found from the single ontology model.
On one hand, a Jess [
Both MDD processes can be executed separately, enabling the decision logic of rule-based applications to be changed regardless of the ontology structure. When the rule model changes, the new rule base can be regenerated and deployed
Platform Independent
Models EMF IPnrteesraecnttiaotnio&n
OWL + SWRL TwoUse Toolkit for OWL & SWRL
Eclipse Modeling
M2M Transformations
Platform Specific Models Java and JSF Web model Jess Rule model
Default Presentation, Navigation, Functionality
M2T Transformations
JET
Code Rule-based Web application Java classes JSF pages
integration Jess rule base into the Web application without a ecting the full architecture. This approach makes Web applications easier to maintain and evolve.
The tool was developed using MDD tools provided in Eclipse, and it is supported by the TwoUse toolkit for the creation of ontology and rule models. Metamodels for representing platform-speci c models in Jess and the Java/JSF are de ned using EMF5 (Eclipse Modeling Framework).
Model-to-model (M2M) transformations are designed with ATL6 (Atlas Transformation Language). The rst one (bottom ow in Fig. 1) maps an ontology and rule model to a Jess platform-speci c model. The second one (top ow in Fig. 1) transforms the ontology model into a Java/JSF Web speci c model.
The outputs of both ATL transformations are the respective inputs of two
model-to-text (M2T) transformations implemented in JET7 (Java Emitter
Templates). As a result, the code for the rule-based Web application is obtained. On
one hand, source les with Jess rules and facts, and on the other hand, the Web
application components, the con guration les, the Java classes, and a
JessEngine Bean which uses the Jess API (Application Programming Interface) to
embed the rule engine into the architecture. Moreover, a set of JSP/JSF web
pages is generated for the user interface which are based on the RichFaces
library [
Architecture of rule-based Web applications
Apache Tomcat business logic
Java Classes JSF + RichFaces pages
Jess Rule set rule engine working memory (facts)
Jess facts
The embedded rule engine manages the Jess rule base and the text le of persistent instances of concepts, called facts. Basically, the rule engine consists of three parts: the working memory contains all the information or facts, the rule set are all the rules, and the rule engine checks whether the rules match the working memory and executes them then.
The Web application enables the user to perform basic functions for instance management (create, list, update and delete instances). Current tools for automatic generation of that kind of Web applications perform those operations on relational databases. The contribution of our approach is that instance management is executed on the rule engine working memory. The rule engine executes a forward-chaining inference mechanism to drive the reasoning process, ring the rules with conditions evaluated as true, and executing their actions to infer new values or modify existing ones.
The use of both rules and AJAX technology improves instance management since each single value is validated and submitted as it is entered by the user, then the rule engine can re suitable rules and deduce new information on the y, driving the instance creation or edition. 4
This tool presentation paper presents a tool that applies MDD to rich Web system development, incorporating a rule engine for deduction and inference. OWL and SWRL formalisms are used as modeling languages by the modeldriven approach.
Since expressiveness in rule-based production systems such as Jess is poorer
than OWL and SWRL semantics, only a subset of those formalisms is currently
supported. Issues related with the combination of rules and ontologies have also
an e ect on the proposed approach. For example, the semantics of OWL and
SWRL adopts an open world assumption, while logic programming languages
such as Jess are based on a closed world assumption. As a consequence, only
DL-Safe SWRL rules [
Another semantic di erence between OWL and classic rule engines such as Jess is related to the fact base and state assertions. While in OWL the ABox containing the assertions about the individuals in the domain can not be modi ed, on the other hand, in a rule-based systems facts can be asserted and modi ed during the inference.
Although these semantic di erences are present, the proposed tool demonstrates how OWL and SWRL can be used as speci cation formalisms in rulebased Web applications development. The bene ts come from the widely use of these formalisms and the many tools available for editing and reasoning over OWL and SWRL speci cations.
The tool is planned to be evaluated in several domains such as pest control in agriculture and medical diagnosis. Future work extends the generated Web application with semantic Web functionalities, such as semantic search based on ontology classes hierarchy as well as instance search.