OK, we need to understand what a SOA is.

That means we need to understand what an ‘architecture’ is and then explore what a ‘service’ is.
Then, we can put both these concepts together and see what an SOA is.

What is an Architecture?

Let’s start by considering a more traditional use of the word Architecture – when it’s used to describe the design of a building.

A nice house, with enough space for you and your family. The balconies are ideal for looking over the surrounding countryside.

But this is what you get...

“Well, I saved bricks by building it ‘in the round’” the builder says.

Yes, but…

He forget that the best view is where he didn’t put any windows.

He just focussed on one aspect, saving bricks, and didn’t take other things into account.
You need to consider the situation you're facing ‘in the round’. (whoops!)

Now, let's scale up the problem...

If we consider cities, as opposed to individual buildings, ‘getting all to work together’ becomes a lot more complex.

Let's apply this to IT...

We all develop software and have written wonderful applications that help many businesses work effectively such as for Sales, Billing and Quality Control but none of them should exist in isolation.

We need them to work together so that, say, a sales enquiry can be used as the basis of an invoice without the need to re-enter what’s being ordered.

We need all our applications to work together so we can save money.  (That’s what it’s all about)

So, we need an architecture for our IT systems

You could just consider the business and ensure that all the systems in it work together effectively and efficiently but, as we’ll see, that’s only half the story.

“No man is an island” is a famous saying, “Business IT systems don’t exist in isolation” is one which is becoming better known.

And, when SOAs become common, so the linkage of systems across businesses will become common as well.

Your Business and the World

Apart from customers, your company probably has suppliers and others who ‘enable’ your business, people such as accountants and consultants.

Taken together, all these organisations make up the world in which your business operates.

My key message...

You must begin to think of your IT system not in isolation but as a way to allow every company (be they suppliers, customers or enablers) involved in your business to work together.

But the role of SOAs isn’t limited to inter-company communication.  In fact, it makes sense to introduce an SOA inside your company before you try to communicate outside.

An SOA is...

Now, let’s explore Service Oriented Architectures.

They are, fundamentally, architectures designed around services.

What is a 'Service'?

Let’s explore what a “service” is…

It’s basically something you do for someone.

Suppose I am a Taxi Driver…

As the example shows, a “requester” requests a service that the “supplier” suppliers.

Characteristics of a Service

Granularity, Granularity, Granularity...

There’s an important word in SOA land – “granularity”.

It’s all too easy to treat everything as a service. That’s not a good idea – not least because you’ll find your IT systems grind to a halt.

Let’s pose a question…

Consider a Billing Application…

OR

And the answer is...

A service to submit an Invoice to a customer is probably closer to meeting the definition of a “Business Oriented Service” in an SOA than a bit of code to read a row from a database.

Put simply, Services should be Business Oriented.

Always ask yourself:

If it’s doable by a human, it’s probably Business Oriented enough to be a Service.  (I’ve not seen this definition anywhere else so, as far I know, it’s original)

Remember, we’re talking architecture, not how to code individual applications.

Where does SOA fit?

Should SOA affect the way you view the whole world?

Or, just the way you write your next line of code?

Try these statements: