What is SOA (Service Oriented Architecture)?

Question

Call me a troll if you want, but I\'m serious: how exactly is the new SOA trend any different than the client-service architecture that I was building 15 years ago?

Answer 1

Let me use the famous whipping boy of Integration Hell: Telco.

Way back in the 90's, cell phone companies were plethoric in my neighborhood, almost as plentiful as the long distance resellers made possible by the communications deregulation of the mid 90's. Well, time goes on, and Bell Atlantic becomes the powerhouse that is Verizon, and swallows up company after company (and at least one Baby Bell). Every single one of these companies has technologies in place, in towers, in switching equipment, in billing systems that are COMPLETELY incompatible with one another.

So the company goes off and says, okay, we have these models for how we do business, let's put a friendly, consistent face on ALL of our technology in the form of WSDL/SOAP/XSD - every language and system we have today can be interfaced to this! Slowly but surely, the company is making all of it's systems capable of reporting on capabilities, being interrogated for load and billing purposes, and exposed for future visionaries to exploit in manners that haven't been accounted for yet.

Anyone can build a SOA client. Anyone with wget and a text editor. And anyone can parse the results (XML).

That is what's fundamentally different from past client/server architectures. I was just talking the other day to someone about interfacing Cobol and Smalltalk based systems to SOA architectures. That's an easy problem to solve. Tell me you can say the same for your DCOM systems.

Answer 2

Most of the answers here seems to convey that SOA (Service Oriented architecture) is about building application in a standardized manner so that other applications can interact with it in platform independent manner.

I am not sure if meaning has changed since but I have had an opportunity to work with a company that offers SOA suite and following are my thoughts on it.

Of course when you design an application you cannot guarantee it will be cross platform compliant. Take for example stock Trading systems. They use Fix protocol to transfer messages. Do you expect it now to return data in XML format so that it can be so called SOA compliant? Definitely not! SOA is an architectural approach that can help you decouple your application/services and let them interact with each other. Backbone of SOA is a ESB (Enterprise Service Bus) which is used to transfer data from one service to other. SOA architecture should take care of formats conversions. For example -

FIX(Service 1) -> (XML ---ESB---> XML) -> JSON (Service 2)

These conversion modules are commonly called as adapters and are generally part of SOA suite. For a bit more information refer to another answer -

Difference between SOA and ESB

Sure SOA is a word is hyped for marketing purpose. Technically speaking it as simple as de-serializing and serializing data so that services can be decoupled and platform independent but the idea behind it is concrete.

Also refer Wiki page for the same.

Answer 3

I think SOA is both a marketing term and an integration of existing solutions with the idea of instead of selling the whole software or machine, we sell the services.

Answer 4

In reality, SOA is a collection of well-defined services. Basically SOA use loosely coupled service to get the desire result easily. Implementation details of a service are hidden from the client/consumer so any change in the implementation doesn’t affect the service until the contract between them is change. Service providers are components that execute some business logic based on predetermined inputs and outputs, and expose this functionality through an SOA implementation. This allows systems based on SOA to respond more quickly and cost effectively for the business. The main difference between component and SOA is that, SOA provide a open standards message which is not specific to any programming language or platform. As a result, you can achieve a high degree of loose coupling and interoperability across platforms and technologies. In a traditional client-server world, the provider will be a server and the consumer will be a client.You can read more about SOA here :Service Oriented architecture (SOA)

Answer 5

SOA is nothing but a way of design, in which the modules comunicates with each others through "services". It is just that, and now the next question is: what is exactly a "service" and what is its difference with a regular "method"??

A service is an operation that performs a single, atomic business operation. This atomicity make it highly reusable from many modules. Then a complex business operation is just the orchestation of the invokation of many of these services in a specific order.

SOA has nothing to do with specific technology, is just an specific way of designing.

Answer 6

Service-oriented architecture (SOA) is a design approach where multiple services collaborate to provide some end set of capabilities. A service here typically means a completely separate operating system process. Communication between these services occurs via calls across a network rather than method calls within a process boundary. SOA emerged as an approach to combat the challenges of the large monolithic applications. It is an approach that aims to promote the reusability of software; two or more end-user applications, for example, could both use the same services. It aims to make it easier to maintain or rewrite software, as theoretically we can replace one service with another without anyone knowing, as long as the semantics of the service don’t change too much.