REST vs. SOAP (Making the Right Architectural Decision) - 1st International SOA Symposium, Amsterdam, October 2008

REST vs. SOAP: Making the Right Architectural Decision Cesare Pautasso Faculty of Informatics University of Lugano (USI), Switzerland http:// www.pautasso.info

Agenda
Motivation: A short history of Web Services
Comparing REST vs. SOAP/WS-*
Architectural Decision Modeling
Conceptual Comparison
Technology Comparison
How to measure the “complexity” of WS-* or the “simplicity” of REST?
Conclusion: Making the right Architectural Decision

Web Sites (1992) HTTP HTML Web Browser Web Server

Web Sites (1992) HTTP HTML Web Browser Web Server (HTTP) SOAP Server Client XML WSDL WS-* Web Services (2000)

RESTful Web Services (2006) Client HTTP PO-XML RSS JSON Web Server WADL WS-* Web Services (2000) (HTTP) SOAP Server Client XML WSDL

XML URI HTTP MIME JSON RESTful SSL RSS

Is REST being used? Slide from Paul Downey, BT

Can we really compare WS-* vs. REST? WS-* REST

Can we really compare WS-* vs. REST? WS-* SOA Middleware Interoperability Standards REST Architectural style for the Web

How to compare? WS-* SOA Middleware Interoperability Standards REST Architectural style for the Web

How to compare? WS-* SOA Middleware Interoperability Standards REST Architectural style for the Web Architectural Decision Modeling

Architectural Decisions
Architectural decisions capture the main design issues and the rationale behind a chosen technical solution
The choice between REST vs. WS-* is an important architectural decision for integration projects
Architectural decisions affect one another
Architectural Decision:
Communication Protocol
Architecture Alternatives:
TCP
SMTP
HTTP
MQ
BEEP
CORBA IIOP
…
Rationale

Application Integration Styles File Transfer Shared Database Message Bus Remote Procedure Call

Application Integration Styles File Transfer Shared Database Message Bus Remote Procedure Call WS-* REST Integration Technology Platform

Related Decisions (WS-*) File Transfer Shared Database Message Bus Remote Procedure Call WS-* REST

Related Decisions (RPC) File Transfer Shared Database Message Bus Remote Procedure Call WS-* REST

Decision Space Overview

Decision Space Summary
21 Decisions and 64 alternatives
Classified by level of abstraction:
3 Architectural Principles
9 Conceptual Decisions
9 Technology -level Decisions

Decision Space Summary
21 Decisions and 64 alternatives
Classified by level of abstraction:
3 Architectural Principles
9 Conceptual Decisions
9 Technology -level Decisions
Decisions help us to measure the complexity implied by the choice of REST or WS-*

Architectural Principles
Protocol Layering
HTTP = Application-level Protocol (REST)
HTTP = Transport-level Protocol (WS-*)
Dealing with Heterogeneity
Loose Coupling

RESTful Web Service Example HTTP Client (Web Browser) Web Server Database GET /book?ISBN=222 SELECT * FROM books WHERE isbn=222 POST /order INSERT INTO orders 301 Location: /order/612 PUT /order/612 UPDATE orders WHERE id=612

Big Web Service Example (from REST perspective) HTTP Client (Stub Object) Web Server POST /soap/endpoint POST /soap/endpoint return new Order() order.setCustomer(x) Web Service Implementation POST /soap/endpoint return getBook(222)

Protocol Layering
“ The Web is the universe of globally accessible information” (Tim Berners Lee)
Applications should publish their data on the Web (through URI)
“ The Web is the universal (tunneling) transport for messages”
Applications get a chance to interact but they remain “outside of the Web”
Application Resource URI HTTP POST Application Endpoint URI POX HTTP GET HTTP PUT HTTP DEL HTTP POST SOAP (WS-*) MQ… SMTP RSS JSON …

Dealing with Heterogeneity
Enterprise Computing
Web Applications
CICS IMS Picture from Eric Newcomer, IONA HTTP

Conceptual Comparison

Technology Comparison

Measuring Complexity
Architectural Decisions give a quantitative measure of the complexity of an architectural design space:
Total number of decisions
For each decision, number of alternative options
For each alternative option, estimate the effort
Decisions with 1 or more alternative options 35 27 Alternatives 14 17 Decisions WS-* REST

Measuring Complexity Decisions with 1 or more alternative options Decisions with more than 1 alternative options 35 27 Alternatives 14 17 Decisions WS-* REST 32 16 Alternatives 12 5 Decisions WS-* REST

Measuring Complexity Decisions with more than 1 alternative options
URI Design
Resource Interaction Semantics
Payload Format
Service Description
Service Composition
32 16 Alternatives 12 5 Decisions WS-* REST

Measuring Complexity Decisions with more than 1 alternative options Decisions with only 1 alternative option 32 16 Alternatives 12 5 Decisions WS-* REST 2 12 Decisions WS-* REST

Measuring Complexity Decisions with only 1 alternative option
Payload Format
Data Representation Modeling
2 12 Decisions WS-* REST

Measuring Effort Decisions with only 1 alternative option Decisions with only do-it-yourself alternatives 2 12 Decisions WS-* REST 0 5 Do-it-yourself Alternatives WS-* REST

Measuring Effort Decisions with only do-it-yourself alternatives
Resource Identification
Resource Relationship
Reliability
Transactions
Service Discovery
0 5 Do-it-yourself Alternatives WS-* REST

Freedom of Choice Freedom from Choice

Comparison Summary
Architectural Decisions measure complexity implied by alternative technologies
REST simplicity = freedom from choice
5 decisions require to choose among 16 alternatives
12 decisions are already taken ( but 5 are do-it-yourself )
WS-* complexity = freedom of choice
12 decisions require to choose among 32 alternatives
2 decisions are already taken (SOAP, WSDL+XSD)

Conclusion
You should focus on whatever solution gets the job done and try to avoid being religious about any specific architectures or technologies.
WS-* has strengths and weaknesses and will be highly suitable to some applications and positively terrible for others. Likewise with REST.
The decision of which to use depends entirely on the application requirements and constraints.
We hope this comparison will help you make the right choice.

References
Cesare Pautasso, Olaf Zimmermann, Frank Leymann,
RESTful Web Services vs. Big Web Services: Making the Right Architectural Decision , Proc. of the 17th International World Wide Web Conference ( WWW2008 ), Bejing, China, April 2008.
Cesare Pautasso, BPEL for REST , Proc. of the 6th International Conference on Business Process Management ( BPM 2008 ), Milan, Italy, September 2008.
Cesare Pautasso, Gustavo Alonso: From Web Service Composition to Megaprogramming Proc. of the 5th VLDB Workshop on Technologies for E-Services (TES-04), Toronto, Canada, August 29-30, 2004.

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REST vs. SOAP (Making the Right Architectural Decision) - 1st International SOA Symposium, Amsterdam, October 2008

by Cesare Pautasso on Oct 14, 2008

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REST vs. SOAP (Making the Right Architectural Decision) - 1st International SOA Symposium, Amsterdam, October 2008 — Presentation Transcript