Service-Oriented Architecture

Thomas Erl is a top-selling IT author, founder of Arcitura Education, and series editor of the Prentice Hall Service Technology Series from Thomas Erl. With more than 300,000 copies in print worldwide, his books have become international bestsellers and have been formally endorsed by senior members of major IT organizations, such as IBM, Microsoft, Oracle, Intel, Accenture, IEEE, HL7, MITRE, SAP, CISCO, HP, and many others. As CEO of Arcitura Education Inc., Thomas has led the development of curricula for the internationally recognized Big Data Science Certified Professional (BDSCP), Cloud Certified Professional (CCP), and SOA Certified Professional (SOACP) accreditation programs, which have established a series of formal, vendor-neutral industry certifications obtained by thousands of IT professionals around the world. Thomas has toured more than 20 countries as a speaker and instructor. More than 100 articles and interviews by Thomas have been published in numerous publications, including The Wall Street Journal and CIO Magazine.

Chapter 1:  Introduction     1
1.1 How Patterns Are Used in this Book     3
1.2 Series Books That Cover Topics from the First Edition     4
1.3 How this Book Is Organized     6
   Part I: Fundamentals     6
      Chapter 3: Understanding Service-Orientation     6
      Chapter 4: Understanding SOA     6
      Chapter 5: Understanding Layers with Services and Microservices     6
   Part II: Service-Oriented Analysis and Design     7
      Chapter 6: Analysis and Modeling with Web Services and Microservices     7
      Chapter 7: Analysis and Modeling with REST Services and Microservices     7
      Chapter 8: Service API and Contract Design with Web Services     7
      Chapter 9: Service API and Contract Design with REST Services and Microservices     7
      Chapter 10: Service API and Contract Versioning with Web Services and REST Services     7
   Part III: Appendices     7
      Appendix A: Service-Orientation Principles Reference     7
      Appendix B: REST Constraints Reference     7
      Appendix C: SOA Design Patterns Reference     8
      Appendix D: The Annotated SOA Manifesto     8
1.4 Page References and Capitalization for Principles, Constraints, and Patterns     8
Additional Information     9
   Symbol Legend     9
   Updates, Errata, and Resources (www.servicetechbooks.com)     9
   Service-Orientation (www.serviceorientation.com)     10
   What Is REST? (www.whatisrest.com)     10
   Referenced Specifications (www.servicetechspecs.com)     10
   SOASchool.com SOA Certified Professional (SOACP)     10
   CloudSchool.com Cloud Certified Professional (CCP)     10
   BigDataScienceSchool.com Big Data Science Certified Professional (BDSCP)     11
   Notification Service     11
Chapter 2: Case Study Backgrounds     13
2.1 How Case Studies Are Used     14
2.2 Case Study Background #1: Transit Line Systems, Inc.     14
2.3 Case Study Background #2: Midwest University Association     15

PART I:  FUNDAMENTALS
Chapter 3:  Understanding Service-Orientation     19
3.1 Introduction to Service-Orientation     20
   Services in Business Automation     21
   Services Are Collections of Capabilities     22
   Service-Orientation as a Design Paradigm     24
   Service-Orientation Design Principles     26
3.2 Problems Solved by Service-Orientation     29
   Silo-based Application Architecture     29
   It Can Be Highly Wasteful     31
   It’s Not as Efficient as It Appears     32
   It Bloats an Enterprise     32
   It Can Result in Complex Infrastructures and Convoluted Enterprise Architectures     33
   Integration Becomes a Constant Challenge     34
   The Need for Service-Orientation     34
   Increased Amounts of Reusable Solution Logic     35
   Reduced Amounts of Application-Specific Logic     36
   Reduced Volume of Logic Overall     36
   Inherent Interoperability     37
3.3 Effects of Service-Orientation on the Enterprise     38
   Service-Orientation and the Concept of “Application”     38
   Service-Orientation and the Concept of “Integration”     40
   The Service Composition     42
3.4 Goals and Benefits of Service-Oriented Computing     43
   Increased Intrinsic Interoperability     44
   Increased Federation     46
   Increased Vendor Diversification Options     47
   Increased Business and Technology Domain Alignment     48
   Increased ROI     48
   Increased Organizational Agility     50
   Reduced IT Burden     52
3.5 Four Pillars of Service-Orientation     54
   Teamwork     54
   Education     55
   Discipline     55
   Balanced Scope     55
Chapter 4:  Understanding SOA     59
Introduction to SOA     60
4.1 The Four Characteristics of SOA     61
   Business-Driven     61
   Vendor-Neutral     63
   Enterprise-Centric     66
   Composition-Centric     68
   Design Priorities     69
4.2 The Four Common Types of SOA     70
   Service Architecture     71
   Service Composition Architecture     77
   Service Inventory Architecture     83
   Service-Oriented Enterprise Architecture     85
4.3 The End Result of Service-Orientation and SOA     86
4.4 SOA Project and Lifecycle Stages     91
   Methodology and Project Delivery Strategies     91
   SOA Project Stages     94
   SOA Adoption Planning     95
   Service Inventory Analysis     96
   Service-Oriented Analysis (Service Modeling)     97
      Step 1: Define Business Automation Requirements     99
      Step 2: Identify Existing Automation Systems     99
      Step 3: Model Candidate Services     100
      Service-Oriented Design (Service Contract)     101
   Service Logic Design     103
   Service Development     103
   Service Testing     103
   Service Deployment and Maintenance     105
   Service Usage and Monitoring     105
   Service Discovery     106
   Service Versioning and Retirement     106
   Project Stages and Organizational Roles     107
Chapter 5:  Understanding Layers with Services and Microservices     111
5.1 Introduction to Service Layers     113
   Service Models and Service Layers     113
   Service and Service Capability Candidates     115
5.2 Breaking Down the Business Problem     115
   Functional Decomposition     115
   Service Encapsulation     116
   Agnostic Context     117
   Agnostic Capability     119
   Utility Abstraction     120
   Entity Abstraction     121
   Non-Agnostic Context     122
   Micro Task Abstraction and Microservices     123
   Process Abstraction and Task Services     123
5.3 Building Up the Service-Oriented Solution     124
   Service-Orientation and Service Composition     124
   Capability Composition and Capability Recomposition     127
      Capability Composition     129
      Capability Composition and Microservices     130
      Capability Recomposition     132
   Logic Centralization and Service Normalization     134

PART II:  SERVICE-ORIENTED ANALYSIS AND DESIGN
Chapter 6:  Analysis and Modeling with Web Services and Microservices     139
6.1 Web Service Modeling Process     140
   Case Study Example     141
   Step 1: Decompose the Business Process (into Granular Actions)     142
   Case Study Example     142
   Step 2: Filter Out Unsuitable Actions     144
   Case Study Example     145
   Step 3: Define Entity Service Candidates     146
   Case Study Example     146
   Step 4: Identify Process-Specific Logic     149
   Case Study Example     149
   Step 5: Apply Service-Orientation     150
   Step 6: Identify Service Composition Candidates     151
   Case Study Example     151
   Step 7: Analyze Processing Requirements     152
   Case Study Example     152
   Step 8: Define Utility Service Candidates     153
   Case Study Example     154
   Step 9: Define Microservice Candidates     154
   Case Study Example     155
   Step 10: Apply Service-Orientation     155
   Step 11: Revise Service Composition Candidates     156
   Case Study Example     156
   Step 12: Revise Capability Candidate Grouping     157
Chapter 7:  Analysis and Modeling with REST Services and Microservices     159
7.1 REST Service Modeling Process     160
   Case Study Example     162
   Step 1: Decompose Business Process (into Granular Actions)     164
   Case Study Example     164
   Step 2: Filter Out Unsuitable Actions     165
   Case Study Example     165
   Step 3: Define Entity Service Candidates     166
   Case Study Example     167
   Step 4: Identify Process-Specific Logic     169
   Case Study Example     169
   Step 5: Identify Resources     170
   Case Study Example     171
   Step 6: Associate Service Capabilities with Resources and Methods     172
   Case Study Example     173
   Step 7: Apply Service-Orientation     174
   Case Study Example     174
   Step 8: Identify Service Composition Candidates     175
   Case Study Example     175
   Step 9: Analyze Processing Requirements     176
   Case Study Example     177
   Step 10: Define Utility Service Candidates (and Associate Resources and Methods)     178
   Case Study Example     179
   Step 11: Define Microservice Candidates (and Associate Resources and Methods)     180
   Case Study Example     181
   Step 12: Apply Service-Orientation     181
   Step 13: Revise Candidate Service Compositions     181
   Case Study Example     182
   Step 14: Revise Resource Definitions and Capability Candidate Grouping     182
7.2 Additional Considerations     183
   Uniform Contract Modeling and REST Service Inventory Modeling     183
   REST Constraints and Uniform Contract Modeling     186
   REST Service Capability Granularity     188
   Resources vs. Entities     189
Chapter 8:  Service API and Contract Design with Web Services     191
8.1 Service Model Design Considerations     193
   Entity Service Design     193
   Utility Service Design     194
   Microservice Design     196
   Task Service Design     196
   Case Study Example     198
8.2 Web Service Design Guidelines     208
   Apply Naming Standards     208
   Apply a Suitable Level of Contract API Granularity     210
   Case Study Example     212
   Design Web Service Operations to Be Inherently Extensible     212
   Case Study Example     213
   Consider Using Modular WSDL Documents     214
   Case Study Example     214
   Use Namespaces Carefully     215
   Case Study Example     215
   Use the SOAP Document and Literal Attribute Values     216
   Case Study Example     217
Chapter 9:  Service API and Contract Design with REST Services and Microservices     219
9.1 Service Model Design Considerations     221
   Entity Service Design     221
   Utility Service Design     222
   Microservice Design     223
   Task Service Design     225
   Case Study Example     226
9.2 REST Service Design Guidelines     231
   Uniform Contract Design Considerations     231
   Designing and Standardizing Methods     231
   Designing and Standardizing HTTP Headers     233
   Designing and Standardizing HTTP Response Codes     235
   Customizing Response Codes     240
   Designing Media Types     242
   Designing Schemas for Media Types     244
   Complex Method Design     246
   Stateless Complex Methods     249
      Fetch Method     249
      Store Method     250
      Delta Method     252
      Async Method     254
   Stateful Complex Methods     256
      Trans Method     256
      PubSub Method     257
   Case Study Example     259
Chapter 10:  Service API and Contract Versioning with Web Services and REST Services     263
10.1 Versioning Basics     265
   Versioning Web Services     265
   Versioning REST Services     266
   Fine and Coarse-Grained Constraints     266
10.2 Versioning and Compatibility     267
   Backwards Compatibility     267
      Backwards Compatibility in Web Services     267
      Backwards Compatibility in REST Services     268
   Forwards Compatibility     271
   Compatible Changes     273
   Incompatible Changes     275
10.3 REST Service Compatibility Considerations     276
10.4 Version Identifiers     279
10.5 Versioning Strategies     282
   The Strict Strategy (New Change, New Contract)     282
      Pros and Cons     283
   The Flexible Strategy (Backwards Compatibility)     283
      Pros and Cons     284
   The Loose Strategy (Backwards and Forwards Compatibility)     284
      Pros and Cons     284
   Strategy Summary     285
10.6 REST Service Versioning Considerations     286

PART III:  APPENDICES
Appendix A:  Service-Orientation Principles Reference     289
Appendix B:  REST Constraints Reference     305
Appendix C:  SOA Design Patterns Reference     317
What’s a Design Pattern?     318
What’s a Design Pattern Language?     320
Pattern Profiles     321
Appendix D:  The Annotated SOA Manifesto     367
The SOA Manifesto     368
The SOA Manifesto Explored     369
   Preamble     370
   Priorities     371
   Guiding Principles     375
About the Author     383
Index     384