Web Services Platform Architecture: SOAP, WSDL, WS-Policy, WS-Addressing, WS-BPEL, WS-Reliable Messaging and More
Read an excerpt:
Chapter 3: Web Services: A Realization of SOA
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Be the First to Write a Review and tell the world about this title!People who purchase this book frequently purchase: - Service-Oriented Architecture: A Field Guide to Integrating XML and Web Services; Thomas Erl, $31.95, 36% Off!
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"Other books claim to present the complete Web services platform architecture,
but this is the first one I've seen that really does. The authors have been
intimately involved in the creation of the architecture. Who better to write
this book?"
--Anne Thomas Manes, Vice President and Research Director, Burton
Group
"This is a very important book, providing a lot of technical detail and
background that very few (if any) other books will be able to provide. The
list of authors includes some of the top experts in the various specifications
covered, and they have done an excellent job explaining the background motivation
for and pertinent details of each specification. The benefit of their perspectives
and collective expertise alone make the book worth reading."
--Eric Newcomer, CTO, IONA Technologies
"Most Web services books barely cover the basics, but this book informs
practitioners of the "real-world" Web services aspects that they need to
know to build real applications. The authors are well-known technical leaders
in the Web services community and they helped write the Web services specifications
covered in this book. Anyone who wants to do serious Web services development
should read this book."
--Steve Vinoski, Chief Engineer, Product Innovation, IONA Technologies
"There aren't many books that are as ambitious as this one is. The most
notable distinguishing factor of this book is that the authors have tried
to pair down the specifications for the user and rather than focusing on
competing specifications, they focus on complementary ones. Nearly every
chapter provides a business justification and need for each feature discussed
in the Web services stack. I would recommend this book to developers, integrators,
and architects."
--Daniel Edgar, Systems Architect, Portland General Electric
"Rarely does a project arrive with such a list of qualified and talented
authors. The subject matter is timely and significant to the industry. "
--Eric Newcomer, author of Understanding SOA with Web Services
and Understanding Web Services and Chief Technology officer, IONA
The Insider's Guide to Building Breakthrough Services with Today's New Web
Services Platform
Using today's new Web services platform, you can build services that are
secure, reliable, efficient at handling transactions, and well suited to
your evolving service-oriented architecture. What's more, you can do all
that without compromising the simplicity or interoperability that made Web
services so attractive. Now, for the first time, the experts who helped
define and architect this platform show you exactly how to make the most
of it.
Unlike other books, Web Services Platform Architecture covers the entire platform.
The authors illuminate every specification that's ready for practical use, covering
messaging, metadata, security, discovery, quality of service, business-process
modeling, and more. Drawing on realistic examples and case studies, they present
a powerfully coherent view of how all these specifications fit together -- and
how to combine them to solve real-world problems.
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Service orientation: Clarifying the business and technical value propositions
-
Web services messaging framework: Using SOAP and WS-Addressing to deliver
Web services messages
-
WSDL: Documenting messages and supporting diverse message interactions
-
WS-Policy: Building services that specify their requirements and capabilities,
and how to interface with them
-
UDDI: Aggregating metadata and making it easily available
-
WS-MetadataExchange: Bootstrapping efficient, customized communication
between Web services
-
WS-Reliable Messaging: Ensuring message delivery across unreliable
networks
-
Transactions: Defining reliable interactions with WS-Coordination,
WS-AtomicTransaction, and WS-BusinessActivity
-
Security: Understanding the roles of WS-Security, WS-Trust, WS-SecureConversation,
and WS-Federation
-
BPEL: Modeling and executing business processes as service compositions
Web Services Platform Architecture gives you an insider's view of the platform
that will change the way you deliver applications. Whether you're an architect,
developer, technical manager, or consultant, you'll find it indispensable.
Preface
"Web services are a mess!"
"There are more than 150 Web services (WS-*) specs!"
"Simple? This stuff is more complicated than CORBA!"
"There is no architecture; just a bunch of competing specs!"
"These specs are denser than plutonium!"
Those are some of the statements we've heard from people"”including our
own colleagues"”about Web services. That's why we wrote this book: to show
that the WS-* platform is not a random walk through a space of WS-* specifications
but rather an organized, structured architecture with well-defined design
and architectural objectives. We apply these objectives when working on
WS-* specifications and when deciding whether or not we need a new specification
in a certain area.
The objective of this book is to present the cohesive, structured architecture
of the Web services platform that we have been helping to define. The architecture
is designed to enable loosely coupled interaction between services with
business-quality reliability, security, and transactional capabilities.
We start by presenting some of the business world"“driving forces that
are motivating the creation of the service-oriented computing platform (Chapter
1, "Service-Oriented Architectures"). Then we focus on Web services as a
realization of this service-oriented computing platform and indicate which
specifications contribute to the platform (Chapter 3, "Web Services"). After
that, we consider each major part of the platform and offer the insight
that went into defining the specifications that govern that component. We
cover the messaging framework, describing metadata, reliable interaction,
security, and service composition in different parts of the book. Before
concluding, we consider two case studies to illustrate how the Web services
platform can address both intranet and extranet integration scenarios. In
the concluding part, we summarize the platform and give our perspectives
on why the integrated architecture we present makes sense and will "win"
the standards battle. Finally, we present our thoughts on the future of
the Web services platform.
At the end of this book, you should no longer feel that Web services has
no architecture or that the architecture is hidden somewhere between 150+
WS-* specifications. You might not agree with our choice of components that
comprise the architecture, but we chose the set based on the fact that those
were designed from the ground up to work together to solve a single problem:
that of being a ubiquitous platform for integrating heterogeneous systems
to enable rich business communication.
Who Should Read This Book?
We wrote this book for technical professionals and students. Although Chapter
2, "Background," briefly introduces the requisite background material about
major XML technologies, we assume that you have a fair grasp of those technologies
coming into this book. Developers who want to understand the overall Web
services platform will appreciate this book. However, this is not a "developer
book" in the sense of providing detailed, code-level understanding. That
was not our objective. Architects, consultants, and technically oriented
management should find this book useful. Students who have already attended
introductory courses in distributed systems or database systems will be
able to understand the Web services platform.
Table of Contents
Foreword
by Steve Mills.
Foreword
by Ronald Schmelzer.
Preface.
Acknowledgments.
About
the Authors.
I. INTRODUCTION.
1. Service-Oriented
Architectures.
Virtual Enterprises.
Business Process Optimization.
Collaborations, Mergers, and Acquisitions.
Resource Sharing.
The Need for Loose Coupling.
Issues with Current Distributed System Technologies.
Advantages of Message-Oriented Middleware.
Future Proofing.
What Is a Service?
Evolution of Major Software Granules.
The Software Version of a Service.
Service-Oriented Architecture.
Bind/Publish/Find.
Framework for SOA.
Summary.
2. Background.
XML.
XML Basics.
DTDs, XML Schema, and RelaxNG.
XML Namespaces.
World Wide Web.
URIs.
HTTP.
MIME.
Summary.
3. Web
Services: A Realization of SOA.
Scope of the Architecture.
Transport Services.
Messaging Services.
SOAP.
WS-Addressing.
Service Description.
WSDL.
Policy.
Discovery Services.
UDDI.
MetaData Exchange.
Quality of Service.
WS-Security.
Reliable Messaging.
Transactions.
Service Components.
Composition of Web Services.
Composeability.
Interoperability.
WS-I.
REST.
"Representational" in REST.
"State Transfer" in REST.
REST Interface Structure.
REST and Web Services.
Scope of Applicability of SOA and Web Service.
Summary.
II. MESSAGING
FRAMEWORK.
4. SOAP.
A Brief History of SOAP.
Architectural Concepts.
Defining Some Terms.
The SOAP Processing Model.
SOAP Roles.
SOAP Faults.
Documents and RPC.
Message Exchange Patterns.
SOAP Bindings.
SOAP
Attachments.
Differences Between SOAP 1.1 and 1.2.
Summary.
5. Web
Services Addressing.
Addressing Web Services.
Architectural Concepts.
Endpoint References.
Comparing Endpoints.
Message Information Headers.
Binding Endpoint References to SOAP Messages.
Request-Reply Pattern in WS-Addressing.
Example.
Future Directions.
Summary.
III.
DESCRIBING METADATA.
6. Web
Services Description Language (WSDL).
Role of WSDL in WS-*/SOA.
History.
Architectural Concepts.
Extensibility.
Support for Multiple Type Systems.
Unifying Messaging and RPC.
Separation of "What" from "How" and "Where".
Support for Multiple Protocols and Transports.
No Ordering.
No Semantics.
WSDL 1.1.
Language Structure.
Best Practices.
Problems and Limitations.
WSDL v2.0.
Overall Language Structure.
Interface Extensions.
Elimination of <message>.
Message Exchange Patterns.
Services.
Features and Properties.
Future Directions.
Summary.
7. Web
Services Policy.
Motivation for WS-Policy.
Architectural Concepts.
Policy Framework.
Attaching Policies to Web Services.
Future Directions.
Summary.
IV. DISCOVERING
METADATA.
8. Universal
Description, Discovery, and Integration (UDDI).
Role of UDDI in SOA and the WS Stack.
Use of UDDI During Design and Development.
Use of UDDI at Runtime.
Motivation for UDDI.
Architectural Concepts.
UDDI V3 Data Model.
UDDI and WSDL.
UDDI and WS-Policy.
UDDI V3 Architecture and APIs.
New Features in UDDI V3.
Future Directions.
Standardization of Taxonomy Language.
Semantic Searching.
Instance-Based Security.
Summary.
9. Web
Services Metadata Exchange.
Architectural Concepts.
Extensibility of Metadata Dialects.
Use of Indirection: Metadata References and Locations.
Metadata Request Operations.
Default Protocol Binding.
Future Directions.
Summary.
V. RELIABLE
INTERACTION.
10. Reliable
Messaging.
Motivation for Reliable Messaging.
The Network Is Reliable.
Latency Is Zero.
There Is One Administrator.
Reliable Messaging Scenarios.
Store and Forward.
Batch Window.
Failure Recovery.
Long-Running Transactions.
Architectural Concepts.
Processing Model.
Sequence Lifecycle.
Basic Syntax.
Sequence Element.
SequenceAcknowledgement Element.
AckRequested Element.
SequenceFault Element.
Delivery Semantics Supported.
Policy Assertions.
Inactivity Timeout.
Retransmission Interval.
Acknowledgement Interval.
Basic WS-Reliable Messaging Profile.
Strengths and Weaknesses.
Examples.
Future Directions.
Summary.
11. Transactions.
Role of Transactions in Web Services/SOA.
Motivation for Transactions.
Classic Transactions.
Business Transactions.
Architectural Concepts.
Definition of Transaction Architectural Terms.
Services and Protocols.
Example.
Travel Agent Scenario Using Atomic Transaction.
Travel Agent Scenario Using Business Activity.
Summary.
VI. SECURITY.
12. Security.
A Motivating Example: Travel Agent Web Services.
Roles of Security in Web Services.
Motivation for Using WS-Security.
End-to-End Security When Intermediaries Are Present.
Federating Multiple Security Domains.
A Brief History.
Architectural Concepts.
Processing Model.
XML Signature.
XML Encryption.
Putting the Pieces Together.
The Basic Model.
Model with Intermediary.
Trust Relationships.
Interoperability.
Basic Security Profile.
Future Directions.
Summary.
13. Advanced
Security.
WS-Trust.
In-Band.
Out-of-Band.
WS-SecureConversation.
WS-Privacy.
WS-Federation.
WS-Authorization.
Web Services Authorization Model.
Security and Policy.
Assertion Model.
Other Security Topics.
Public-Key Cryptography.
Non-Repudiation.
Data Integrity and Data-Origin Authentication.
Proof of Message Origin.
Proof of Message Receipt.
Delivery of Proof of Message Receipt.
Summary.
VII.
SERVICE COMPOSITION.
14. Modeling
Business Processes: BPEL.
Motivation for BPEL.
A Brief History.
Architectural Concepts.
Overview of the Process Composition Model.
Abstract and Executable Processes.
Recursive, Type-Based Composition.
Process Instance Lifecycle.
Event Handling.
Dealing with Exceptional Behavior.
Extensibility and the Role of Web Services Policies.
BPEL Processing Model.
Deployment.
Interacting with the Process.
Navigating the Process Model.
Scopes and Handlers.
Future Directions.
Summary.
VII.
CASE STUDIES.
15. Case
Study: Car Parts Supply Chain.
Scenario Description.
Architecture.
Web Service Descriptions.
Messages and Protocols.
Summary.
16. Case
Study: Ordering Service Packs.
Scenario Description.
Architecture.
Web Service Descriptions.
Messages and Protocols.
Summary.
IX. CONCLUSION.
17. Futures.
Semantics.
Wiring.
Ordering Constraints.
Contracting.
Summary.
18. Conclusion.
A Summary of the Web Services Platform.
Standardization.
Concerns About the Standardization Process.
Competing Specifications.
Perspectives.
Why Will It Succeed?
Risks.
Building on the Core Platform.
Summary.
References.
Index.
About the Authors
Sanjiva Weerawarana, research staff member for the component systems group
at IBM Research, helps define and coordinate IBM's Web services technical strategy
and activities. A member of the Apache Software Foundation, he contributed to
many specifications including the SOAP 1.1 and WSDL 1.1 specifications and built
their first implementations.
Francisco Curbera, IBM research staff member and component systems group manager,
coauthored BPEL4WS, WS-Addressing, and other specifications. He represents IBM
on the BPEL and Web Services Addressing working groups.
Frank Leymann directs the Institute of Architecture of Application Systems
at the University of Stuttgart. As an IBM distinguished engineer, he helped
architect IBM's middleware stack and define IBM's On Demand Computing strategy.
IBM Fellow Tony Storey has helped lead the development of many of IBM's middleware,
Web services, and grid computing products.
IBM Fellow Donald F. Ferguson is chief architect and technical lead for IBM
Software Group, and chairs IBM's SWG Architecture Board.
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