RESTful Web Services vs. Big Web Services: Making the Right Architectural Decision

Transcription

1 ful Web Services vs. Big Web Services: Making the Right Architectural Decision Cesare Pautasso Olaf Zimmermann Frank Leymann University of Lugano IBM Zurich Research Lab University of Stuttgart Switzerland Switzerland Germany 1

2 The only religious quote 2

3 Can we really compare vs.? 3

4 Can we really compare vs.? Middleware Interoperability Standards Architectural style for the Web 4

5 How to compare? Middleware Interoperability Standards Architectural Decision Modeling Architectural style for the Web 5

6 Architectural Decisions Architectural decisions capture the main design issues and the rationale behind a chosen technical solution The choice between vs. is an important architectural decision for integration projects Architectural decisions affect one another Architectural Decision: Communication Protocol Architecture Alternatives: 1. TCP 2. SMTP 3. HTTP 4. MQ 5. BEEP 6. CORBA IIOP 7. Rationale 6

7 Application Integration Styles Shared Database Remote Procedure Call Message Bus File Transfer Integration Technology Platform 7

8 Related Decisions () Shared Database Remote Procedure Call Message Bus File Transfer 8

9 Related Decisions (RPC) Shared Database Remote Procedure Call Message Bus File Transfer 9

10 Decision Space Overview 10

11 Outline 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 or 11

12 Architectural Principles 1. Protocol Layering HTTP = Application-level Protocol () HTTP = Transport-level Protocol () 2. Dealing with Heterogeneity 3. Loose Coupling 12

13 ful Web Service Example HTTP Client (Web Browser) Web Server Database GET /book?isbn=222 POST /order 301 Location: /order/612 POST /order/612 SELECT * FROM books WHERE isbn=222 INSERT INTO orders UPDATE orders WHERE id=612 13

14 HTTP Client (Stub Object) Big Web Service Example (from perspective) Web Server Web Service Implementation POST /soap/endpoint POST /soap/endpoint POST /soap/endpoint return getbook(222) return new Order() order.setcustomer(x) 14

15 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 POX RSS JSON SOAP () HTTP GET HTTP POST HTTP PUT HTTP DEL SMTP HTTP POST MQ Resource URI Application Endpoint URI Application 15

16 Dealing with Heterogeneity Web Applications Enterprise Computing HTTP CICS IMS Picture from Eric Newcomer, IONA 16

17 Conceptual Comparison 17

18 Technology Comparison 18

19 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 Alternatives Decisions with 1 or more alternative options 19

20 Measuring Complexity Decisions Alternatives Decisions with more than 1 alternative options Decisions Alternatives Decisions with 1 or more alternative options 20

21 Measuring Complexity Decisions Alternatives Decisions with more than 1 alternative options URI Design Resource Interaction Semantics Payload Format Service Description Service Composition 21

22 Measuring Complexity Decisions Alternatives Decisions with more than 1 alternative options Decisions 12 2 Decisions with only 1 alternative option 22

23 Measuring Complexity Payload Format Data Representation Modeling Decisions 12 2 Decisions with only 1 alternative option 23

24 Measuring Effort Do-it-yourself Alternatives 5 0 Decisions with only do-it-yourself alternatives Decisions 12 2 Decisions with only 1 alternative option 24

25 Measuring Effort Do-it-yourself Alternatives 5 0 Decisions with only do-it-yourself alternatives Resource Identification Resource Relationship Reliability Transactions Service Discovery 25

26 Freedom of Choice Freedom from Choice 26

27 Comparison Summary Architectural Decisions measure complexity implied by alternative technologies simplicity = freedom from choice 5 decisions require to choose among 16 alternatives 12 decisions are already taken (but 5 are do-it-yourself) complexity = freedom of choice 12 decisions require to choose among 32 alternatives 2 decisions are already taken (SOAP, WSDL+XSD) 27

28 Conclusion You should focus on whatever solution gets the job done and try to avoid being religious about any specific architectures or technologies. has strengths and weaknesses and will be highly suitable to some applications and positively terrible for others. Likewise with. 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. 28

29 PhD positions available! Cesare Pautasso University of Lugano, Switzerland 29

30 What is a nice URI? Prefer Nouns to Verbs Keep them Short +switzerland&layer=&ie=utf8&z=12&om=1&iwloc=addr 30