SOA: Service-Oriented Architecture

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1 SOA: Service-Oriented Architecture Dr. Kanda Runapongsa Department of Computer Engineering Khon Kaen University 1 Gartner Prediction The industry analyst firm Gartner recently reported that By 2006, 60 percent of the $527 billion IT professional services industry will be based on exploiting Web services and technology By 2008, 80 percent of all software development would be based on SOA This means that more than half of all software development will revolve around the Web technology 2 Overview SOA Definition Loose Coupling Software Agents Service Provider Service Consumer Deriving Web Services from SOA SOAP Web Services REST Web Services Web 2.0: The Global SOA 3 Dr. Kanda Runapongsa, Computer Engineering, Khon Kaen University 1

2 SOA Definition Things should be made as simple as possible, but no simpler. -- Albert Einstein SOA is an architectural style whose goal is to achieve loose coupling among interacting software agents 4 Loose Coupling As we build more software systems, we see similar situations and patterns Naturally, we want to reuse the functionality of existing systems rather than building them from scratch 5 Real vs. Artificial Dependencies A real dependency is a state of affairs in which one system depends on the functionality provided by another If the world only contained real dependencies, Einstein s test would have been satisfied long time ago The problem is that we also create artificial dependencies along with real dependencies 6 Dr. Kanda Runapongsa, Computer Engineering, Khon Kaen University 2

3 Make Things Simpler We cannot remove artificial dependencies, but we can reduce them As artificial dependencies are reduced, we have achieved loose coupling Artificial dependencies should be reduced to the minimum but real dependencies should not be altered 7 Service Definition A service is a unit of work done by a service provider to achieve desired end results for a service consumer Both provider and consumer are roles played by software agents on behalf of their owners An agent is a program acting on behalf of a person or organization 8 Why do We Need a Service? We want experts to do work for us We are not experts in everything Consuming a service is usually cheaper and more effective than doing the work ourselves 9 Dr. Kanda Runapongsa, Computer Engineering, Khon Kaen University 3

4 An Example of SOA The CD player offers a CD playing service If you want to play it, put your CD into a CD player and the player plays it for you You can play the same CD on a portable player or on your expensive stereo The quality of service is different 10 SOA and OOP It is not a replacement for Object Oriented Programming (OOP) Architecture (which SOA falls into) Sets which functionality the system should perform, split the functionality between components Design (which OOP falls into) Design drill down in to the details relating to implementing certain components 11 How SOA Achieves Loose Coupling How does SOA achieve loose coupling among interacting software agents A small set of simple and ubiquitous interfaces to all participating software agents Descriptive messages constrained by an extensible schema delivered through the interfaces 12 Dr. Kanda Runapongsa, Computer Engineering, Khon Kaen University 4

5 Interfacing Interfacing is expensive and errorprone for distributed applications An interface needs to prescribe system behavior Difficult to implement correctly across different platforms and languages Instead of building new interfaces for each application, reuse a few generic ones for all applications 13 Messages Messages must be descriptive, rather than instructive The service provider is responsible for solving the problem Messages must be written in a format, structure, and vocabulary that is understood by all parties The more restricted a message is, the easier it is to understand 14 Extensibility The world is an ever-changing place and so is any environment in which a software system lives These changes demand corresponding changes in Software system Service consumers Service providers Messages they exchange 15 Dr. Kanda Runapongsa, Computer Engineering, Khon Kaen University 5

6 Service Discovery An SOA must have a mechanism that enables a consumer to discover a service provider Under the context of a service sought by the consumer The mechanism can be really flexible It does not have to be a centralized registry 16 Additional Constraints Additional constraints for SOA to improve its scalability, performance, and reliability Stateless Service Stateful Service Idempotent Request 17 Stateless Service Each message that a consumer sends to a provider must contain all necessary information for the provider to access it Make a service provider more scalable The provider does not have to store state information between requests Service in mass production Each request can be treated as generic 18 Dr. Kanda Runapongsa, Computer Engineering, Khon Kaen University 6

7 Stateless Example Service provider class counter { int count = 0; int add(int a) { count = count + a; return count; } } Service client add(2) --> Get the result as 2 add(3) --> Get the result as 3!!! 19 Stateful Service Stateful service is difficult to avoid in a number of situations One situation is to establish a session between a consumer and a provider Stateful services require both the consumer and the provider to share the same consumer-specific context Reduce the overall scalability Increase coupling 20 Idempotent Request Duplicate requests received by a software agent have the same effects as a unique request This constraint allows providers and consumers to improve the overall service reliability by simply repeating the request if faults are encountered 21 Dr. Kanda Runapongsa, Computer Engineering, Khon Kaen University 7

22 Deriving Web Services from SOA A Web service is a SOA with at least the following additional constraints Interfaces must be based on Internet protocols such as HTTP, FTP, and SMTP Except for

8 22 Deriving Web Services from SOA A Web service is a SOA with at least the following additional constraints Interfaces must be based on Internet protocols such as HTTP, FTP, and SMTP Except for binary data attachment, messages must be in XML 23 Two Styles of Web Services SOAP web services Except for binary data attachment, messages must be carried by SOAP The description of a service must be in WSDL REST web services A REST web service is an SOA based on the concept of resource A resource is anything that has a URI 24 Dr. Kanda Runapongsa, Computer Engineering, Khon Kaen University 8

9 A SOAP Web Service A SOAP web service is the most common and marketed form of web service in the industry SOAP acts like an envelope that carries its contents Two flavors of SOAP web services SOAP RPC web services are not SOA Document-centric SOAP web services are SOA 25 A SOAP RPC Web Service A SOAP RPC web service breaks the second constraint required by an SOA A SOAP RPC web service encodes RPC (remote procedure calls) in SOAP messages Effectively, it prescribes both system behaviors and application semantics 26 REST Web Services REST web services require little infrastructure support apart from standard HTTP and XML processing REST web services are simple and effective HTTP is the most widely available interface 27 Dr. Kanda Runapongsa, Computer Engineering, Khon Kaen University 9

10 The History of the Term Web 2.0 Web 2.0 was originally coined by O Reily s Dale Dougherty It was to describe the forces behind the huge success of Internet companies and applications Companies: Google, ebay, Amazon, itunes Applications: Wikipedia, BitTorrent 28 What is Web 2.0? Web 2.0 describes Web experiences that fundamentally engage users by Allow them to participate in sharing information and enriching data freely Readily offering their core functionality as open services to be composited or mashed up into new services and sites Placing the Web at the center of the software experience both in terms of data location as well as where the software is 29 Web 2.0 Architecture 30 Dr. Kanda Runapongsa, Computer Engineering, Khon Kaen University 10

11 Web 2.0 Characteristics Tim O Reilly provides seven classic characteristics of Web 2.0 software Web as platform Harnessing collective intelligence Data is the next Intel inside End of the software release cycle Lightweight programming models Software above the level of a single device Rich user experience 31 Web as Platform Software and services are now the same thing The Web has become a computing platform in its own right The Web is where most software is moving for cost, convenience, agility, and increased overall value 32 Harnessing Collective Intelligence The network effects of massive amounts of users make the collaborative Web a much more potent force than stand-alone software Online collaborative entities such as Wikepedia are a network effect of the combined contributions of their users Classic example of Web Dr. Kanda Runapongsa, Computer Engineering, Khon Kaen University 11

12 Data is the Next Intel Inside The core functionality of many modern information systems is not software It s the valuable data within the system that is actually more important Google s search database Amazon s products and associated reviews The data these sites posses are their real assets 34 End of the Software Release Cycle When software is on the Web, upgrading becomes a different experience Upgrades and improvements to service are instantly available and encouraged to be as nondisruptive as possible 35 Lightweight Programming Models When the clients of Web software are numerous and diverse Complex standards can get in the way Web 2.0 leverages the easiest methods that work well Lead to simpler services such as REST and RSS instead of SOAP and WS-* standards 36 Dr. Kanda Runapongsa, Computer Engineering, Khon Kaen University 12

13 Software Above the Level of a Single Device PCs are an increasingly smaller aspect of the Web With so many different devices such as mobile phones, PDAs, and even digital video recorders becoming connected to the Web Providing and consuming functionality and connectivity The software as a Service landscape of the Web now includes these in the picture 37 Rich user Experiences The Web has ceased to be about static Web pages They still exist, but they are much less important The AJAX browser application model is famously a Web 2.0 technique Provide the full interactive experience of native applications to the user Leveraging XML Web services on the backend to provide access to data and services 38 Comparison of Web 2.0 and SOA Concepts Web 2.0 SOA Service Model Perferred Service Standards Web services HTTP, XML, RSS, REST Web services WSDL, UDDI, SOAP, BPEL, WS-* 39 Dr. Kanda Runapongsa, Computer Engineering, Khon Kaen University 13

14 Comparison of Web 2.0 and SOA Concepts Composition Mechanisms Reusability User Interface Web 2.0 Web server aggregation (remixing, mash-ups) Yes, very Yes, explicit with AJAX and emphasis on RIAs SOA Orchestration, coordination, service wrapping Yes, somewhat No, implicit 40 Comparison of Web 2.0 and SOA Concepts Web 2.0 SOA Design Patterns AJAX Syndication Multi-device software Service Layer Service Bus Unit of Work Idempotent Message Reservation Point-to-Point Channel Publish- Subscribe Channel Content Routing 41 Comparison of Web 2.0 and SOA Concepts Web 2.0 SOA Architectural Principles Enhancement by extension Autonomy Radical Test Participation Loose Coupling Reusability Personalization Autonomy Statelessness Service Contracts Interface First Design Loose Coupling Consumability 42 Discoverability Dr. Kanda Runapongsa, Computer Engineering, Khon Kaen University 14

15 Comparison of Web 2.0 and SOA Concepts Web 2.0 SOA Core Competenci es Software as a Service, Control over data sources Trusting users as codevelopers Harnessing collective intelligence Functional encapsulation Data as an asset System and data integration B2B selfservice Open standards 43 SOA vs. Web 2.0 What SOA and Web 2.0 Shares Open access via standards. Embrace Web services Encourage composition and reuse What SOA and Web 2.0 Differs SOA usually has a more complex, hardwired service model Web 2.0 encourages simpler, malleable forms with clear overlap in the middle. 44 Connections between Web 2.0 and SOA Web 2.0 can indeed be conceptualized as a Global SOA Already ousting millions of services and thousands of composite applications Businesses that are currently implementing SOA will need to connect their Web-facing apps to their internal SOAs Further use and composition by their business partners and customers 45 Dr. Kanda Runapongsa, Computer Engineering, Khon Kaen University 15

16 How Web 2.0 and SOA Complete Each Other Web 2.0 emphasizes a social aspect that SOA is completely missing Web 2.0 talks about presentation and the front end is displayed to the user SOA is largely silent on the issue of presentation, though it admits its existence SOA has much more central configuration control while Web 2.0 has no command and control structure 46 Web 2.0 and SOA Conclusion Web 2.0 is really the Global SOA available to the whole world today Web 2.0 will also be connected to your local SOA in ways you will need Be prepared to leverage Web 2.0 and SOA and reap the benefits of these emerging mindsets and toolkits 47 References XML.com, What is Service-Oriented Architecture, The Agile Developer, SOA does not replace OOP, SOA Web Services Journal, Web 2.0 The Global SOA, 48 Dr. Kanda Runapongsa, Computer Engineering, Khon Kaen University 16

Introduction to SOA & Web 2.0

Introduction to SOA & Web 2.0 Asst. Prof. Dr. Kanda Runapongsa Saikaew (krunapon@kku.ac.th) Department of Computer Engineering Khon Kaen University 10/12/09 1 Overview Gartner Top 10 Technologies SOA Definition