How to talk to the world...

Messages, Messages and, yes, Messages!

To communicate, you use ‘messages’ (which explains the last item in the list on the What is a SOA? page).

We’ll look at what messages contain in a moment – for now, imagine them like text messages sent to your mobile phone.

Implementation Approaches

You can do it all yourself.

Or, you can use a product from suppliers like IBM, Iona, Sonic Software or CapeClear

If you use a product, you get added value like tools to manage the flow of messages.

Enterprise Service Bus

One of the implementation mechanisms is to use an “Enterprise Service Bus” (ESB)

As its name implies, it’s designed for use within an Enterprise – that’s another name for a company.

Basically, it lets you wrap your existing applications up and get them talking to each other

Many vendors maintain that SOA = ESB but, in fact, it’s just one possible implementation.

Nonetheless, it’s a good way to think about implementing an SOA.

This is the standard diagram used to explain the ESB:

As you see, you add something called an “adaptor” to each of your existing applications. This allows them to deliver services to other applications.

Typically, ESB products also add a set of tools to let you administer and monitor the traffic over the ESB.

What goes along the Bus?

Yes, hopefully, you’ve guessed…

Messages, messages and more messages.

Typically, these are implemented as Web Services.

What's a Web Service?

At an implementation level, a Web Service is a service delivered by XML encoded messages.

However, there’s a much broader view – that they will allow the Web to be used to share knowledge, rather than just look at information. There’s a good introduction to this in Tim Berners-Lee’s article on the “Semantic Web” in the May 2001 issue of Scientific American.

The Benefits of Web Services

When you link your ESB to one of your suppliers, you can use the Internet to send and receive messages.  Nearly everyone is on the Internet so it makes sense to use an existing communication medium.

From a more practical viewpoint, an increasing number of development tools support Web Services 'out of the box'.