Semantic Interoperability

Submitted by fokus on Tue, 08/19/2008 - 14:34
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Semantic Interoperability

Semantic interoperability is achieved when the meaning of exchanged information is understood by applications and services. Achieving semantic interoperability, i.e. mastering semantic heterogeneity, today is seen as one of the biggest challenges for the integration of information systems. Basically, this is due to the fact that meaning changes by context and over time and different requirements in different domains result in different information models. The focus of this work package is on identifying semantic integration approaches, analysing semantic capabilities of FOSS middleware and FOSS forges, developing exemplary platform enhancements (proof-of-concepts) and performing experiments based on these developments.

The following figure illustrates how the semantic interoperability work package is structured.

The following document provides a short and precise overview of the of the developed semantic interoperability approaches and components, the experiments carried out and the conclusions drawn:

In the following, the various tasks and results are described in more detail.

State-of-the-art Evaluation, Identification of Important Issues and Requirements

In order to provide a foundation for the discussion of open challenges and important issues with regard to semantic interoperability in the FOSS domain information on state-of-the-art semantic technologies and corresponding Open Source tools are collected. Several knowledge models and knowledge representation languages as well as their underlying semantics are discussed. Furthermore, in this context the Semantic Web initiative and the technologies it has produced are discussed. The exchange of information between different applications is strongly related with the thematic topic of application integration. Hence, various standards and Free Open Source tools which have emerged in the area of semantically described Web Services.

Having captured the technological and conceptual state-of-the-art a holistic approach towards semantic interoperability of FOSS is followed, addressing FOSS itself as well as its development. In order to improve semantic interoperability of FOSS on a large scale, the semantic integration capabilities of Open Source middleware have to be addressed in the first place. Hence, semantic middleware services are analysed which are of fundamental relevance and which promise to deliver quick wins for semantic application integration problems.
The second goal is related to the development process of FOSS. A considerable number of collaborative FOSS development platforms (so called forges) can be found. In order to tap the full potential of the European FOSS community, the exchange of information (e.g. documentation, project tasks, source code) between different collaboration platforms is needed. In fact, this is more a semantic than a technical challenge. Hence, important issues and potential approaches towards the semantic interoperability of FOSS forges are discussed.

Semantic Capabilities of FOSS Middleware and Forges; Requirements Specification and Conceptual Model for Enhancements

Based on the identification of important issues and requirements (see above), selected semantic interoperability enhancements of FOSS middleware and FOSS forges are addressed.
The idea is to focus on a set of exemplary developments in order to demonstrate how semantic technologies can be used to cope with the diversity and heterogeneity of software and services in the FOSS domain. More specifically, five semantic interoperability areas were selected for further investigation: Semantic mapping, semantic-based Web service integration, semantic harmonisation of security policies, semantics-based cross-forge search and cross-forge project migration. For each of these areas semantic interoperability approaches are developed based on existing FOSS tools and middleware platforms. A detailed requirements specification and conceptual models for the selected developments are provided.

Development of Platform Enhancements

For each of the selected exemplary semantic interoperability approaches (see above) for FOSS middleware and FOSS forges a proof-of-concept (PoC) is developed. The detailed architecture is presented and described. Moreover, technological problems experienced and lessons learnt are reflected. The development is carried out in an iterative way. The idea behind using an iterative process is to start with a simple implementation of the core system functionality and then develop new as well as revise and modify existing parts of the system until the complete system is implemented.

The following document represents a collection of artefacts created in the iterative development process (class diagrams, interaction diagrams, test cases, code documentation etc.). The document in the development phase only project-internally. This is why the document contains various links to resources that are accessible only by QualiPSo project partners. Nevertheless it might be of interest for readers in order to understand the technical realization of the various PoCs.

The main outcome of this task are the developed proof-of-concept implementations. A brief description for each proof-of-concept and a link to the project (containing source code, installation guides etc.) is provided below. For conceptual details on the approach and on the implementation please have a look at the documents listed above.

OSS Middleware Platform Enhancements

Semantic Business Process Integration

The integration and composition of Web services from different domains (organisational domains and/or application domains) raises significant interoperability challenges due to the heterogeneous information models used to describe and interact with the services. The de-facto industry standard for service composition and process integration is BPEL. A concept for incorporating rule-based semantic mappings (so called semantic bridges) into BPEL and for extending Free Open Source BPEL engines with semantic mapping capabilities was elaborated. The necessary FOSS BPEL engine extensions are implemented along with a prototypical composition tool that supports the user in the integration process.

Semantic Harmonisation of Security Policies

The goal of the SecureComm implementation is the creation of a security “mediator” module deployable in an Open Source Enterprise Service Bus (ESB) middleware. The module mediates among service consuming applications (clients) and service providing applications (servers). The purpose of the mediation is to bridge incompatible security models implemented in applications that should interoperate. Ontology mapping allows bridging to be designed and implemented at a conceptual level.

Semantic Mapping Testing

The analysis of information integration approaches provided in D3.1.1b revealed that semantic mapping, i.e. ontology mapping, is a central semantic middleware service. Hence, rule-based ontology mappings are fundamental to most of the other semantic interoperability platform enhancements developed within this work package. However, ontology mapping is a complex and error-prone process. In order to determine the quality of mappings, users and developers need to be enabled to systematically test the semantic mappings created by domain experts. An approach and a tool for the systematic testing of rule-based ontology mappings has been developed.

Semantic Interoperability Enhancement for OSS Forges

Semantics-based Cross Forge Project Migration

Taking into account the high number of existing OSS forges (just in Europe more than 50) the exchange of information between different forges is desirable. In fact, this is more a semantic than a technical challenge. The interoperability of different collaborative OSS development platforms has not been addressed so far. This proof-of-concept demonstrates an approach for enabling the migration of projects or their parts between OSS forges. Bearing in mind the heterogeneity of forges, a presented approach assumes that the data model of each platform is described by its own ontology. In the project migration process semantic mapping is applied to achieve interoperability.

Semantics-based Cross Forge Search

Users of OSS forges demand efficient and precise search engines for retrieving content, such as projects, users, documentation, bug reports etc. The scatteredness of the OSS forges landscape forces users who are searching for a piece of software to start the search in one forge and to repeat it in other OSS forges. Moreover, since different forges apply different information models (e.g. different project categorisations), the search criteria have to be modified accordingly. This proof-of-concept demonstrates how semantic technologies and semantic mapping approaches can be leveraged to search for artefacts across heterogeneous OSS forges.

Semantic Interoperability Experiments, Scenarios and Evaluation

Based on the developed proof-of-concepts real scenarios are developed and experiments are carried out in order to evaluate the semantic interoperability approaches. The OSS middleware tools and platform enhancements are applied to align different information models, to achieve the semantically sound interoperation of heterogeneous services, to align security policies etc. Moreover, semantic interoperability scenarios for searching and migrating projects across heterogeneous OSS forges are developed and demonstrated. The experienced benefits and problems are assessed.

Conclusions, Strategy and Roadmap Definition

Roadmaps for the adoption of the developed semantic interoperability approaches in the problem-specific domains, e.g. in the OSS forges domain and in the OSS middleware domain, are worked out. Relevant steps and open research issues are described. Finally, common aspects for future semantic interoperability R&D are identified.

Semantic interoperability - Platform enhancements and experiments

This document provides a short and precise overview of the above described tasks, i.e of the developed semantic interoperability platform enhancements, the experiments carried out and the conclusions drawn.