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Can someone explain in plain english what is SOA all about? I hear SOA here, SOA there but I cannot understand exacly what it is and what is used for. Was it some simple concept and later evolved into something huge or what?
All documents, including wiki are a bit abstract or maybe I'm an idiot and don't get it. Is there an idiot's guide on this?
What exactly is there behind these three letters?
SOA is a new badge for some very old ideas:
Divide your code into reusable modules.
Encapsulate in a module any design decision that is likely to change.
Design your modules in such a way that they can be combined in different useful ways (sometimes called a "family" or "product line").
These are all bedrock software-development principles, many of them first articulated by David Parnas.
What's new in SOA is
You're doing it on a network.
Modules are communicating by sending messages to each other over the network, rather than by more tradtional programming-language mechanisms like procedure calls. In particular, in a service-oriented architecture the parts generally don't share mutable state (global variables in a traditional program). Or if they do share state, that state is carefully locked up in a database which is itself an agent and which can easily manage multiple concurrent clients.
You might find this article (What is SOA? - SOA and Web Services Explained ) helpful.
A little teaser:
SOA is a style of architecting applications in such a way that they are composed of discrete software agents that have simple, well defined interfaces and are orchestrated through a loose coupling to perform a required function.
There are 2 roles in SOA- a service provider and a service consumer. A software agent may play both roles. SOA is not an entirely new concept – however, this article mainly focuses on SOA as implemented with web services.
I see many answers explaining a Service Oriented Architecture (SOA) using even more advanced words and technical terms. I'd like to give a shot at explaining it for the layman, using an analogy in plain english.
But first a description of a SOA
SOA could be described in three layers as seen in the picture below. On one side we have the Provider and on the other side we have the Consumer, separated by a Bridge where the two sides communicate.
The consumer uses a number of Applications necessary for it's business and the provider uses Components that provide these applications with information. They communicate through a set of Services using a common architecture.
The analogy
Imagine a house on the country side, that in many ways is part of a larger community, like a city or town. The city has it's own complex systems for providing water and electricity, handling sanitation, providing transportation and other utilities. The House is the consumer in this model, the City (or community) is the provider and the pipes, sewers, powerlines, optical fibers etc. is the Infrastructure in which they communicate.
This model could loosely be compared to a SOA. The people in the house uses a number of different "applications" like radiators, computers, toilets, lamps, underfloor heating, bathtubs etc. These applications don't care how the city generates the water, creates the electricity or handles the waste as long as it works. The components of the city are generators, water pumps and sanitation areas. It provides the house with all these needs but it's up to the house to use it in what ever way it sees fit.
I hope this gave at least someone a better picture of a SOA.
Let's assume you have four cooks. In SOA, you assume they hate each other, so you strive to let them have to talk to each other as little as possible.
How do you do that? Well, you will first define the roles and interface -- cook 1 will make salad, cook 2 will make soup, cook 3 will make the steak, etc.. Then you will place the dishes well organised on the table (so these are the interfaces) and say, "Everybody please place your creation into your assigned dishes. Don't care about anybody else.".
This way, the four cooks have to talk to each other as little as possible, which is very good in software development -- not necessarily because they hate each other, but for other reasons like physical location, efficiency in making decisions etc.
It also means you can recombine the dishes (services) as you like. For example, you might just use the dessert to service a cafe, or just take the soup and combine it with a bread you bought from another company to provide a cheaper menu, or let other restaurants use your salads to combine with their dishes, etc.
One of the most successful implementation of SOA was at Amazon. Because of their design, they could re-package their whole infrastructure and sell it as Amazon Web Service.
*This is only one aspect of SOA.
SOA is an architectural style but also a vision on how heterogeneous application should be developped and integrated. The main purpose of SOA is to shift away from monolithic applications and have instead a set of reusable services that can be composed to build applications.
IMHO, SOA makes sense only at the enterprise-level, and means nothing for a single application.
In many enterprise, each department had its own set of enterprise applications which implied
Similar feature were implemented several times
Data (e.g. customer or employee data) need to be shared between
several applications
Applications were department-centric.
With SOA, the idea is to have reusable services be made available enterprise-wide, so that application can be built and composed out of them. The promise of SOA are
No need to reimplement similar features over and over (e.g.
provide a customer or employee service)
Facilitates integration of applications together and the access
to common data or features
Enterprise-centric development
effort.
The SOA vision requires an technological shift as well as an organizational shift. Whereas it solves some problem, it also introduces other, for instance security is much harder with SOA that with monolithic application. Therefore SOA is subject to discussion on whether it works or not.
This is the 1000ft view of SOA. It however doesn't stop here. There are other concepts complementing SOA such as business process orchestration (BPM), enterprise service bus (ESB), complex event processing (CEP), etc. They all tackle the problem of IT/business alignement, that is, how to have the IT be able to support the business effectively.
SOA is acronym for Service Oriented Architecture.
SOA is designing and writing software applications in such a way
that distinct software modules can be
integrated seamlessly with high degree
of re-usability.
Most of the people
restrict SOA as writing client/server
software-web-services. But it is too
small context of SOA. SOA is much
larger than that and over the past few
years web-services have been primary
medium of communcation which is
probably the reason why people think
of SOA as web-services in general
restricting the boundaries and meaning
of SOA.
You can think of writing a database-access module which is so independent that it can work on its own without any dependencies. This module can expose classes which can be used by any host-software that needs database access. There's no start-up configuration in host-application. Whatever is needed or required is communicated through classes exposes by database-access module. We can call these classes as services and consider the module as service-enabled.
Practicing SOA gives high degree of
re-usability by enforcing DRY [Don't
repeat your self] which results into
highly maintainable software.
Maintainability is the first thing any
software architecture thinks of - SOA
gives you that.
As far as I understand, the basic concept there is that you create small "services" that provide something useful to other systems and avoid building large systems that tend to do everything inside the system.
So you define a protocol which you will use for interaction (say, it might be SOAP web services) and let your "system-that-does-some-business-work" to interact with the small services to achieve your "big goal".
I would suggest you read articles by Thomas Erl and Roger Sessions, this will give you a firm handle on what SOA is all about. These are also good resources, look at the SOA explained for your boss one for a layman explanation
Building a SOA
SOA Design Pattern
Achieving integrity in a SOA
Why your SOA should be like a VW Beetle
SOA explained for your boss
WCF Service Performance
what tends to happen in large organizations is that over time everything is either monolithic or disparate systems everywhere or a little of both. Someone eventually comes in and says we've got a mess. Now, you want to re-design (money to someone) everything to be oriented in a sort of monotlithic depends on who you pay paradigm but at the same time be able to add pieces and parts independently of the master/monolith.
So you buy Oracle's SOA and Oracle becomes the boss of all your parts. All the other players coming in have to work with SOA via a service (web service or whatever it has.) The Oracle monolith takes care of everything (monolith is not meant derogatory). Oh yeah, you got ASP.NET MVC on the front or something else.
main thing is moving things in and out of they system without impact and keeping the vendor Oracle SOA, Microsoft WCF, as the brains of it all. everything's all oop/ood like, fluid, things moving in and out with little to no impact, even human services, not just computers.
To me it just means a bunch of web services (or whatever we call them in the future) with a good front end. And if you own the database just hit the database and stop worrying about buzzwords. it's okay.
Only one suggestion:-
Read SOA Concepts, Technology and Design by Thomas Erl.
It has very beautifully given the details about SOA in plain English and with case studies.
Well You see.. SOA stands for Service Oriented Architecture.... In simplest words, you write a piece of code that is very generic i.e. it does some thing that can be used in a lot of applications ... may be something like a address book or may be a calculator. and you launch this code on the IIS. So you provide a service through your code. So you are a service provider. Now someone wants to use a similar code then he does not have to write the code again. He simply uses your code maybe through a web service. Hence he becomes a service consumer. Hence making a program using such services is called SOA. And the loose coupling is there as the service provider and consumer may be interacting even if they are using diff programming languages.
Hope you understand.
from ittoolbox blogs.
The following outlines the similarities and differences to past design techniques:
• SOA versus Structured Programming
o Similarities: Most similar to subroutine calls where parameters are passed and the operation of the function is abstracted from the caller - e.g. CICS link and execute and the COBOL CALL reserved word. Copybooks are used to define data structure which is typically defined as an XML schema for services.
o Differences: SOA is loosely coupled implying changes to a service have less impact to the consumer (the "calling" program) and services are interoperable across languages and platforms.
• SOA versus OOA/OOD
o Similarities: Encapsulation, Abstraction and Defined Interfaces
o Differences: SOA is loosely coupled with no class hierarchy or inheritance, Low-level abstractions - class level versus business service
• SOA versus legacy Component Based Development (CBD) - e.g. CORBA, DCOM, EJB
o Similarities: Reuse through assembling components, Interfaces, Remote calls
o Differences: Wide adoption of standards, XML Schemas vs. Marshaled Objects, Service Orchestration, Designing for reuse is easier, services are business focused vs. IT focused, business services are course grained (broad in scope)
• SOA (for integration) versus Enterprise Application Integration (EAI)
o Similarities: Best practices (well defined interfaces, standardized schemas, event driven architecture), reusable interfaces, common schemas
o Differences: Standards, adoption, and improved tools
Reading the responses above, it sounds to me that SOA is what developers (good ones at least) have been doing from day one.
It could also stand for "Struct of Arrays" (as opposed to "Array of Structs") which is a common topic in parallel (especially SIMD) programming, but I'm guessing that's not what you mean here!
SOA is a buzzword that was invented by technology vendors to help sell their Enterprise Service Bus related technologies. The idea is that you make your little island applications in the enterprise (eg: accounting system, stock control system, etc) all expose services, so that they can be orchestrated flexibly into 'applications', or rather become parts of aggregate enterprise scoped business logic.
Basically a load of old bollocks that nearly never works, because it misses the point that the reasons why technology is the way it is in an organisation is down to culture, evolution, history of the firm, and the lock in is so high that any attempt to restructure the technology is bound to fail.
Have a listen to this week's edition of the Floss Weekly podcast, which covers SOA. The descriptions are pretty high level and don't delve into too many technical details (although more concrete and recognizable examples of SOA projects would have been helpful.
A traditional application architecture is:
A user interface
Undefined stuff (implementation) that's encapsulated/hidden behind the user interface
If you want to access the data programmatically, you might need to resort to screen-scraping.
SOA seems to me to be an architecture which focus on exposing machine-readable data and/or APIs, instead of on exposing UIs.
SOA or Service-Oriented Architecture is a software architecture pattern in which applications or systems are constructed from underlying (and usually distributed) software services that conform to a specific set of characteristics, namely:
Interface, Policy and Contract based
Location transparency
Autonomous
Abstract
Reusable
Composable
Stateless
Discoverable
Extensible
Loosely coupled
The primary goal of SOA is sofware development agility, i.e. the ability to respond the change easily, and cheaply, thus allowing businesses to rapidly respond to changing markets.
Services are typically (but by no means exclusively) implemented as web services, i.e. they operate over the ubiquitous web HTTP protocol, and are implemented either using XML-based SOAP or the lightweight (and more popular) REST paradigm.
Depends on who you are!
If you're an business owner, SOA is a solution to increase your incomes and business agility. If you're an entreprise architect, SOA is a way to draw nice and clean piece of software on a blank canvas. If you're an architect SOA is the solution to design loosely coupled services over an integration platform, to just plug services into outlets. If you're a developper SOA is a programming paradigm where a service is in the center of the design and the code.
You should read 100-SOA-Questions [pdf]
Cheers
Service Oriented Architecture (SOA) is a software architectural style that builds applications as a collection of pluggable parts, each of which can be reused by other applications.
I frequently hear Service-Oriented Architecture (SOA) being tossed around as a buzzword among non-technical customers or program managers with little concern or understanding for what it actually entails (example: "Can I buy a SOA?"). There's also a lot of misinformation about SOA (example: "Only web apps can use SOA") and a general lack of understanding for its capabilities (example: "SOA can make your make all of your data work together").
What are some key facts that you, as someone who understand the technical side of SOA, use to educate program managers on the appropriate use and understanding of SOA? What's the best way to set the record straight with non-technical folks?
For non technical people I would use the following concept. The whole professional world is service oriented.
Instead of baking a cookie by
youself, you go to the baker.
Instead of trying to cure yourself,
you go to the doctor.
Instead of writing a program, you
ask a programmer to do this for
you.
This implies two major advantages:
Each one does his job better than if
we all were trying to solve all our
tasks separately.
There is a way, which allows non
professionals to communicate with
those, who will solve our task (in
real world such way is money and
business contracts)
In the world of software such architecture is implemented by defining specialized services (applications) which are dedicated to perform specific tasks and by defining protocols, which are solving problem of communications between such applications.
When such architecture is deployed, you get some benefits, which can be also mapped to the real world:
If doctor is unavailable, you cannot
be cured but at least you can get a
cookie from the bakery! In software this means one failed service does not break the whole system.
Usually doctors and bakers do not share the same room and this allows them to operate better. Just like in software you can place each service on its own hardware.
For software world this means, better availability, maintainability, reuse, and reduced costs.
Good luck!
"SOA is like hiring new employees when the job gets too large for the current team." Each part of the whole system is analogous an employee. Managers understand employees ;)
Maybe you have some applications in your company to use as a demonstration.
Try to show them the big picture with lots of loosely dependent services with some common needs/features created by various teams, and pulling out those embedded but commonly used features and use them as service providers.
The other thing that came into my mind is to show them the various connectors that the services can use to communicate (maybe there are some really old screenscraping legacy apps). Also, the message bus concept with normalizing and transaction handling needs to be clarified. In my opinion, non-technical people should see this whole SOA concept as loosely coupled services talking to each other with any kind of messages, where services are written/managed/governed by different teams (so formal service declarations and SLAs can come handy).
Try to avoid mentioning vendors, if possible. Or mention lots of vendors and technologies for each part in order to show them the various options.
Let's suppose I have a large middleware infrastructure mediating requests between several business components (customer applications, network, payments, etc). The middleware stack is responsible for orchestration, routing, transformation and other stuff (similar to the Enterprise Integration Patterns book by Gregor Hohpe).
My question is: is it good design to put some business logic on the middleware?
Let's say my app A requests some customer data from the middleware. But in order to get this data, I have to supply customer id and some other parameter. The fetching of this parameter should be done by the requesting app or is the middleware responsible for 'facilitating' and providing an interface that receives customer ids and internally fetches the other parameter?
I realize this is not a simple question (because of the definition of business logic), but I was wondering if it is a general approach or some guidelines.
Apart from the routing, transformation and orchestration, performance should be kept in mind while loading middleware with functional requirements. Middlware should take a fraction of the entire end-to-end transaction life time. This can be achieved only by concentrating on the middleware core functionalities, rather than trying to complement the host system functionalities.
This is the "Composite Application" pattern; the heart of a Service Oriented Architecture. That's what the ESB vendors are selling: a way to put additional business logic somewhere that creates a composite application out of existing applications.
This is not simple because your composite application is not just routing. It's a proper new composite transaction layered on top of the routing.
Hint. Look at getting a good ESB before going too much further. This rapidly gets out of control and having some additional support is helpful. Even if you don't buy something like Sun's JCAPS or Open ESB, you'll be happy you learned what it does and how they organize complex composite applications.
Orchestration, Routing and Transformation.
You don't do any of these for technical reasons, at random, or just for fun, you do these because you have some business requirement -- ergo there is business logic involved.
The only thing you are missing for a complete business system is calculation and reporting (let us assume you already have security in place!).
Except for very low level networking, OS and storage issues almost everything that comprises a computer system is there because the business/government/end users wants it to be there.
The choice of 'Business Logic' as terminoligy was very poor and has led to endless distortions of design and architecture.
What most good designers/architects mean by business logic is calculation and analysis.
If you "%s/Business Logic/Calculation/g" most of the architectural edicts make more sense.
The middleware application should do it. System A should have no idea that the other parameter exists, and will certainly have no idea about how to get it.