The Role of Metadata in the Orchestration of Web Services

Inhaltsverzeichnis (Table of Contents)

• 1 Preface
• 2 Process Management and Web Services
  • 2.1 Enterprise Application Integration
  • 2.2 Workflow Management Systems
  • 2.3 From EAI and WfMS to Web Services
• 3 Introduction to XML-Technologies
  • 3.1 Extensible Markup Language
    • 3.1.1 Well-formed vs. valid
    • 3.1.2 XML Namespaces
  • 3.2 Document Type Definition
  • 3.3 XML Schema Definition
  • 3.4 The Extensible Stylesheet Language
  • 3.5 XML Path Language
  • 3.6 XML Query Language
• 4 Introduction to Web Services
  • 4.1 Service Oriented Architecture
  • 4.2 Web Service
  • 4.3 Basic Web Service Technologies
    • 4.3.1 SOAP
    • 4.3.2 Web Service Description Language
    • 4.3.3 Public and Private Registries
      • 4.3.3.1 Universal Description, Discovery, and Integration
      • 4.3.3.2 Representing Information within UDDI
      • 4.3.3.3 Representing Businesses and Providers
      • 4.3.3.4 Representing Services
      • 4.3.3.5 Representing Web Services
      • 4.3.3.6 Technical Models
• 5 Web Services in a Business World
  • 5.1 Web Service Orchestration
    • 5.1.1 Orchestration Requirements
    • 5.1.2 Orchestration Standards
  • 5.2 Business Process Executing Language for Web Services
    • 5.2.1 Document Structure
    • 5.2.2 Variables in BPEL
    • 5.2.3 Service Selection
    • 5.2.4 Activities
      • 5.2.4.1 Implementing Structured Activities
    • 5.2.5 Exceptions and Transactions
    • 5.2.6 Instance Routing
• 6 Realization
  • 6.1 Scenario Overview
  • 6.2 System Environment
    • 6.2.1 J2EE for Web Service Implementation
      • 6.2.1.1 JAX-WS
    • 6.2.2 The Oracle BPEL Process Manager for WS Orchestration
  • 6.3 Implementation
    • 6.3.1 Database Structure
      • 6.3.1.1 Connecting to the MySQL Database
    • 6.3.3 Building a JAX-WS Web service
    • 6.3.3 Developing the BPEL Process
      • 6.3.3.1 Dynamic Binding with WS-Addressing
      • 6.3.3.2 Dynamic Procurement Process Steps

Zielsetzung und Themenschwerpunkte (Objectives and Key Themes)

This diploma thesis aims to explore the role of metadata in the orchestration of web services. It investigates how metadata facilitates efficient and effective integration of different web services within a business context.

• The importance of metadata in web service orchestration.
• The use of XML technologies for metadata management.
• The application of BPEL (Business Process Execution Language) for web service orchestration.
• Practical implementation of a web service orchestration system.
• The challenges and opportunities of dynamic web service binding.

Zusammenfassung der Kapitel (Chapter Summaries)

2 Process Management and Web Services: This chapter lays the groundwork by introducing enterprise application integration (EAI) and workflow management systems (WfMS). It explores the evolution from traditional EAI and WfMS approaches to the more flexible and standardized approach offered by web services. The chapter highlights the limitations of older methods and positions web services as a superior solution for managing complex business processes, emphasizing the increased interoperability and scalability they afford. Key concepts like message-broker-based EAI are discussed, providing a historical context for the advancements presented later in the thesis concerning web service orchestration.

3 Introduction to XML-Technologies: This chapter provides a detailed overview of key XML technologies crucial for understanding web service architecture and metadata management. It comprehensively covers the Extensible Markup Language (XML) itself, differentiating between well-formed and valid XML documents and explaining the importance of XML namespaces. Further, the chapter delves into Document Type Definition (DTD), XML Schema Definition (XSD), the Extensible Stylesheet Language (XSLT), XML Path Language (XPath), and XML Query Language (XQuery). Each technology is explained in detail, highlighting its role in defining data structures, validating documents, and querying XML data, all vital elements for effective metadata handling within a web service environment.

4 Introduction to Web Services: This chapter introduces the fundamental concepts of web services and their underlying architecture. It thoroughly explains Service-Oriented Architecture (SOA) and elaborates on the characteristics and benefits of web services in general. The core web service technologies – SOAP (Simple Object Access Protocol), WSDL (Web Services Description Language) – are explained, underscoring their roles in communication and service description. A significant portion is dedicated to UDDI (Universal Description, Discovery, and Integration), exploring its function as a registry for discovering and integrating web services. This section details how UDDI represents information about businesses, providers, and services, clarifying the mechanisms for service location and interaction. The chapter effectively sets the stage for later chapters by establishing a firm understanding of the core technologies used in the thesis.

5 Web Services in a Business World: This chapter transitions from the technical aspects of web services to their application within a business context. It focuses on web service orchestration, defining its requirements and exploring standardization efforts. A primary focus is on BPEL (Business Process Execution Language for Web Services), detailing its document structure, variable handling, service selection mechanisms, and different activity types. The chapter describes how BPEL facilitates the coordination and management of multiple web services within complex business processes, underscoring its role in achieving robust and efficient business workflows. The discussion of exceptions, transactions, and instance routing illustrates BPEL's capabilities in handling complex scenarios and ensuring reliable execution. This chapter directly connects the theoretical foundations established in previous chapters with the practical applications of web services.

Schlüsselwörter (Keywords)

Metadata, Web Services, Orchestration, XML, BPEL, SOA, UDDI, SOAP, WSDL, J2EE, JAX-WS, Web Service Description Language, Enterprise Application Integration, Workflow Management Systems, Dynamic Binding, WS-Addressing.

Frequently Asked Questions: A Comprehensive Language Preview

What is the purpose of this document?

This document provides a comprehensive preview of a language-focused text, including the table of contents, objectives and key themes, chapter summaries, and keywords. It serves as a concise overview to understand the structure and content of the complete work.

What topics are covered in the document?

The document covers process management, web services, XML technologies, and the orchestration of web services using BPEL (Business Process Execution Language). It explores topics such as enterprise application integration (EAI), workflow management systems (WfMS), service-oriented architecture (SOA), SOAP, WSDL, UDDI, and the practical implementation of web services using J2EE and JAX-WS.

What is the focus of the main chapters?

Chapter 2 introduces process management and web services, outlining the evolution from traditional EAI and WfMS to web services. Chapter 3 details key XML technologies like XML, DTD, XSD, XSLT, XPath, and XQuery. Chapter 4 introduces core web service technologies including SOAP, WSDL, and UDDI. Chapter 5 focuses on web service orchestration within a business context, emphasizing BPEL. Finally, Chapter 6 discusses the practical realization of a web service orchestration system, covering the system environment and implementation details.

What are the key themes or objectives of the document?

The main objective is to explore the role of metadata in web service orchestration. Key themes include the importance of metadata, XML technologies for metadata management, the application of BPEL, practical implementation of a web service orchestration system, and the challenges and opportunities of dynamic web service binding.

What are the key technologies discussed?

The document discusses various technologies, including XML, DTD, XSD, XSLT, XPath, XQuery, SOAP, WSDL, UDDI, BPEL, J2EE, and JAX-WS. These technologies are central to understanding the architecture and implementation of web services and their orchestration.

What is the significance of metadata in the context of this document?

Metadata plays a crucial role in facilitating the efficient and effective integration of different web services. The document investigates how metadata contributes to the orchestration process and improves the overall management of complex business processes.

What is the role of BPEL in this context?

BPEL (Business Process Execution Language) is a key technology used for web service orchestration. The document details its application in coordinating and managing multiple web services within complex business processes, allowing for the creation of robust and efficient workflows.

What practical implementation aspects are covered?

The document covers the practical implementation of a web service orchestration system, including the system environment (J2EE, Oracle BPEL Process Manager), database structure (MySQL), building a JAX-WS web service, and developing the BPEL process, emphasizing dynamic binding using WS-Addressing.

What are the keywords associated with this document?

Key words include Metadata, Web Services, Orchestration, XML, BPEL, SOA, UDDI, SOAP, WSDL, J2EE, JAX-WS, Web Service Description Language, Enterprise Application Integration, Workflow Management Systems, Dynamic Binding, and WS-Addressing.