Interoperability in eGovernment through Cross-Ontology Semantic Web Service Composition E-Book
Nils Barnickel
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- Herausgeber: GRIN Verlag
- Sprache: Englisch
Diploma Thesis from the year 2006 in the subject Computer Science - Applied, grade: 1,0, Free University of Berlin (Institut für Informatik), language: English, abstract: Due to the heterogeneous structure of the public sector, the achievement of interoperability is a key challenge for comprehensive electronic government. Service-oriented architectures lay the foundation for flexible application integration and process-orientation through Web service composition. Semantically enriched Web services promise to increase the level of automation and to reduce integration efforts significantly. Furthermore, a relatively high degree of formality in key areas of government activities encourages the application of Semantic Web concepts. This diploma thesis presents an approach for semi-automatically supporting the design and execution of data flows within the composition of semantically described Web services that are making use of different ontologies and data representations. The approach includes a rule-based mechanism for user-transparent mediation between ontologies. In order to validate the approach, a prototypical cross-ontology Semantic Web service composition tool has been implemented to be used in eGovernment scenarios spanning multiple application domains. The essence of this thesis was presented at the European Semantic Web Conference 2006 at the Workshop on eGovernment and Semantic Web and is published in the paper.
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Veröffentlichungsjahr: 2011
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Abstract
Due to the heterogeneous structure of the public sector, the achievement of interoperability is a key challenge for comprehensive electronic government. Service oriented architectures lay the foundation for exible application integration and process-orientation through Web service composition. Semantically enriched Web services promise to increase the level of automation and to reduce integration eorts signicantly. Further-more, a relatively high degree of formality in key areas of government activities encourages the application of Semantic Web concepts.
This diploma thesis presents an approach for semi-automatically supporting the design and execution of data ows within the composition of semantically described Web services that are making use of dierent ontologies and data representations. The approach includes a rule-based mechanism for user-transparent mediation between ontologies. In order to validate the approach, a prototypical cross-ontology Semantic Web service composition tool has been implemented to be used in eGovernment scenarios spanning multiple application domains.
The essence of this thesis was presented at the European Semantic Web Conference 2006 at the Workshop on eGovernment and Semantic Web and is published in the paper [1].
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Zusammenfassung
Aufgrund der heterogenen Struktur des öentlichen Sektors ist das Erreichen von Interoperabilität eine wesentliche Herausforderung für umfassendes eGovernment. Service-orientierte Architekturen bilden die Grundlage für exible Anwendungsintegration und Prozessorientierung durch die Komposition von Web-Services. Semantisch beschriebene Web-Services versprechen dabei den Grad der Automatisierung zu erhöhen und damit den Integrationsaufwand zu senken. In diesem Zusammenhang ermöglicht der relativ hohe Formalisierungsgrad der Aktivitäten im öentlichen Sektor die Anwendung von Semantic-Web-Technologien.
Diese Diplomarbeit präsentiert einen Ansatz für die semi-automatische Unterstützung bei Entwurf und Ausführung des Datenusses innerhalb der Komposition von semantisch beschriebenen Web-Services, die unterschiedliche Ontologien und Datenrepräsentationen verwenden. Der Ansatz beinhaltet einen regelbasierten Mechanismus für die transparente Mediation zwischen Ontologien. Um den Ansatz zu validieren, wurde ein Prototyp für die ontologien-übergreifende Komposition von semantischen Web-Services entwickelt. Dieser wird verwendet, um eGovernment-Szenarios zu realisieren, die mehrere Domänen überspannen.
Die Essenz dieser Arbeit wurde auf der European Semantic Web Conference 2006 im Workshop zu eGovernment und Semantic Web präsentiert und in [1] veröentlicht.
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1 Introduction
This chapter elaborates the motivation for the thesis. It gives an insight into the relation between the domain of electronic government (eGovernment) and Semantic Web research. It outlines the interoperability challenges in eGovernment process integration and domain specic conditions, which encourage the application of Semantic Web concepts. Furthermore, the goals of this thesis are explained and the scope of this work is claried. Finally, an outline of the thesis is given in the last section.
1.1 Motivation
Electronic Government is a term for describing the application of information and communication technology (ICT) in public sector processes. Focus is put on process reengineering to achieve more eective and ecient public sector activities and to enhance the relationship between citizen and government. eGovernment covers a wide range of elds such as eDomocracy or eHealth, which is discussed in more detail in chapter 2. One cross-eld problem is the integration of processes whenever dierent public agencies are involved in an activity. Processes are backed by ICT systems and applications have to be interconnected to seamlessly support process integration. In order to enable process integration, applications need to provide interfaces which are accessible by other applications. The demand for process integration has arisen from many domains, which has lead to standardized interfaces and protocols for inter-application communication. In the last years Web services [2] have taken the lead role in this eld. Today XML-based standards such as WSDL, SOAP and BPEL [3] are widely used for describing, composing and invoking Web services to achieve process integration. These technologies represent the foundation for establishing syntactical interoperability between dierent applications. But semantic interoperability issues are left open. Because the semantics of Web services are not described explicitly they can not be automatically processed. Thus, necessary steps for composing services are primarily done manually, which leads to a high degree of complexity. For example, in a rst step of composing appropriate services have to be selected from hierarchical repositories [4, 5], whereas the specic category for each service needs to be known a priori. Having chosen appropriate services a user needs to understand their implicit semantics in order to design the control ow and data ow.
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With respect to the multitude of services participating in a process the creation of the data ow, i.e. the parameter assignments between the activities is a complex task and it requires the user to have and extensive knowledge about the underlying type representations.
In particular, when using services from dierent application domains comprehensive data type transformations have to be added manually due to existing dierent information representations.
The idea of bringing implicitly dened service semantics to an explicit level by providing machine understandable Web service descriptions with formally dened semantics promises to ease the composition process. The long term vision is to enable dynamic goal-oriented service composition and to use powerful inference engines and matchmaking mechanisms, in order to automate the whole composition process including discovery, composition, execution and interoperation of Web services. As it has been argued in [6] on the road towards this goal still many problems need to be solved, whereby each
further step can increase the level of automation.
The interconnection between eGovernment and Semantic Web research is twofold: On the one hand from the perspective of Semantic Web research eGovernment provides an ideal testbed. Due to the heterogeneity of information space in eGovernment, it provides the challenge to achieve interoperability for process integration in a largely distributed environment. At the same time the eGovernment domain exhibits a high degree of formality in key areas imposed by laws and regulations, thus encouraging the application of Semantic Web concepts based on formal modeling and description logics. On the other hand from the perspective of eGovernment research Semantic Web technologies are the key for semantic interoperability in process integration and represent the foundation for achieving the vision of a knowledge-based, user centric, distributed and networked eGovernment [Mg2006].
1.2 Goals and Scope
As discussed before, achieving interoperability is an extensive process and thus often leads to signicant obstacles in process integration. Therefore, this thesis aims at reducing the complexity of process integration by means of enhancing interoperability. Chapter 3 describes the state-of-the-art in this context and elaborates the three dierent aspects of interoperability namely technical, semantic, and organizational aspects. Whereas this work focuses on semantic interoperability.
In particular, this thesis elaborates an approach for semi-automatic design of data ows within the composition of semantically described eGovernment Web services across different domains making use of dierent information representations.
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This thesis does not target automated planning as known in the context of articial intelligence research. The approach aims at easing the composition task by semi-automatic data ow design but leaves the planning task (i.e. which services to include at which part into the composition) to the eGovernment process expert. The data ow design should be supported by graphical modeling, which guides the process expert through the composition design and recommends parameter assignments between involved services. Thus, the technical and complex data ow design is shifted on a more abstract level. Necessary type transformation due to dierent information representations will be kept transparent from the design process. The core concept of the thesis will be the integration of a mechanism into the visual composition design realizing mediation between dierent information representations based on Semantic Web technologies. However, with respect to already existing or early evolving eGovernment Web services the approach should be realized as an additional layer on top of existing technology. The concept should allow to express the mediation on the level of domain models rather than on application level, so that mappings between dierent information representations only need to be dened once. Furthermore, the concept should take into account the realistic perspective, that dierent domain models and resulting information representations need to evolve relatively independent from each other to serve best for their domain. Additionally, the mediation mechanism has to provide a level of expressiveness that enables complicated mappings between information representations from dierent domain models. And at the same time the mechanism should be easy to handle to assure maintainability.
To validate the approach a prototypical composition tool has been developed, which includes a graphical composer and an execution engine to run the composed services. However, the tool assumes that all services involved in a composition have already been discovered. In order to focus on the data ow challenges, the composition description only allows to dene sequences of services and no further control ow design is supported. As input the tool requires eGovernment service descriptions and mappings between their dierent domain models. As the result of the composition design, an execution plan of the composed services specied in a proprietary format has been elaborated. Additionally, an execution engine has been realized which interprets the execution plan. Furthermore, it will be outlined how this execution plan, which is based on Semantic Web technology, can be mapped to existing industry languages for business process execution such as BPEL. The thesis will not focus on organizational questions, e.g. how to manage the representation of domain models and their mutual mappings. Chapter 6 refers back to the goals presented in this section to evaluate whether and how far they have been reached.
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1.3 Overview
Chapter 2 introduces into the domain of eGovernment and describes challenges arising from process integration. Subsequently, the motivation on how these issues can be addressed by applying Semantic Web concepts is outlined. Furthermore, an eGovernment scenario spanning multiple domains is presented to demonstrate the aforementioned integration challenge. The scenario is taken as a reference point in subsequent chapters. Finally, the chapter highlights the evolvement from eGovernment to eGovernance and points out its relation to this work.
The state-of-the-art is presented in Chapter 3. It gives information how the challenges in process integration can be addressed and sets the background for the later presented approach. The dimensions of interoperability are analyzed and related to the thesis goals. Base technologies for achieving interoperability are presented including Web Services, Web Service composition, Semantic Web services and information integration approaches. Finally, related work in the context of Web service composition support is presented.
Chapter 4 explains the concept of the developed approach for cross-ontology Semantic Web service composition. After specifying the requirements for the concept, the general idea of lifting the abstraction level in Web service composition is explained. Starting with an overview the dierent aspects of the concept are presented including domain ontologies and Semantic Web services, semantic bridges, the matching mechanism for data ow design and the process execution. Finally, a logical architecture for the concept is illustrated.
Chapter 5 deals with the implementation of the developed prototype. The implementation is divided into three parts: composition design, composition execution and scenario. Based on an illustrated system architecture the realization of the dierent components is explained. Finally, the validation and verication of the realized prototype is described and the usage of the prototype is claried.
Chapter 6 covers the evaluation of the presented approach. It analyzes to which extent the goals set in section 1.2 have been met. Furthermore, the impact of the presented approach on a large scale is analyzed.
Chapter 7 summarizes the presented approach and outlines the problems that have been left open. Moreover, it gives an outlook on future work.
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2 eGovernment
2.1 Fields of eGovernment
Electronic Government is a term for describing the application of information and communication technology (ICT) in the elds of state activity divided in its three branches legislature, judiciary and executive. It aims to improve operational processes in all three branches by re-engineering of traditional processes towards increased eectiveness and eciency and enhancement of participation and involvement of citizens. Each branch targets the aforementioned goals from its specic perspective. Applications in the legislature fall into categories such as eDemocracy or eParticipation. eDemocracy aims at enabling more direct democracy. By improving the citizen's awareness and knowledge through better information access and by easing the voting process through online voting, referendums could be held more frequently. eParticipation targets the involvement of citizens in public aairs. The idea is to increase participation, by for example online forums and polls based on open communicated government activities. Consequently, transparency increases, which in the long run should lead to a more accountable government.
Applications within the judiciary focus on assistance in legal processes. Terms like eJudice describe the application of trust and security technologies, e.g. digital identication. Furthermore, legal processes can be enhanced by legal knowledge based systems. The objective is to achieve better quality and eciency in decision making processes as well as improved accuracy and consistency. Thereby, legal documents as laws and regulations, which are the foundation for decision making in legal processes, are modeled by trying to extract the semantics and logical relationships within these documents. Thus, expert systems using inference machines can be developed to support the mentioned goals.
The executive branch is in charge of the implementation of law, thus opening a wide range of operational processes. Here, the focus of eGovernment or eAdministration in particular, is on process automatization and on process re-engineering to achieve more eective and ecient public administration and public services. Process re-engineering often includes process integration that raises interoperability problems, which are addressed in this thesis. As process integration is relevant in all three eGovernment elds but in particular in eAdministration the next section covers it in more detail.
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2.2 eAdministration
eAdministration covers a wide range of activities. Activities comprise the provision of online public services as online resident registration, online application of ocial documents such as a birth certicate, online application for social aid or online tax declaration for businesses to name a few examples. Another eld of activity for instance is to improve the administration in the health sector (eHealth), where lots of documents of patient data or treatment calculations need to be processed. An additional promising eld is eProcurement. The idea is that online aggregation of procurement orders from dierent collaborating agencies can reduce purchase prices due to large-scale orders. These various activities can be categorized into the following interaction elds:
•G2C: public services delivery from government to citizens
•G2B: public services delivery from government to businesses
•G2N: public services delivery from government to non-governmental organizations or to the non-prot third sector
•G2G: public services delivery from government to other governmental agencies on local, regional, or inter-/national level
However G2C, G2B and G2N interactions to deliver services from the front-oce often include G2G interactions with back-oces from other governmental agencies. Within these interaction elds the following interaction levels can be divided:
