Nutshell Definitions

When conducting the Practical SOA workshops in different Australian cities last month, I felt the need to explain a few concepts for my audience in very simple and memorable terms. I realised I have already been doing this for myself for a long time. I try and distil a concept into a single word, or at most a short phrase, in order to understand it. This has been very useful to me in evaluating the merits of technologies and comparing them to others. Call these my trade secrets which I'm now sharing with you :-).

OK, so here are some of my definitions of popular terms, each in a nutshell:

Service-Oriented Architecture (SOA):

1. In one word, dependencies. More precisely, it is the science of analysing and managing dependencies - making implicit dependencies explicit and eliminating unnecessary dependencies between systems. That's what it's all about.

2. Alternative definition: Lego-isation of the Enterprise, i.e., refactoring the various application silos in an enterprise into reusable building blocks based on their core functions.

Middleware:

That which converts organisational silos into Lego blocks.

Integration:

This is a tricky one. When you point your browser at a website and the page loads, no one thinks of it as integration. For something to be recognised as "integration", it seems it cannot afford to appear effortless! For this reason, I steer clear of trying to define integration in terms of technology. The best integration is seamless and not seen as such. It's an art that involves dependency management (see the definition of SOA above). Minimalism is a virtue here, and appropriate data design is an unacknowledged part of integration.

Governance, as opposed to plain old Management:

Governance has suddenly become a very fashionable word, and not just in IT. "Corporate governance" is a phrase that is parrotted by commentators when they often mean just management. So what's the difference?

In a nutshell,
Governance is about doing the right thing, the "what", the "goal".
Management is about doing things right, the "how", the "task".

Cloud computing as opposed to conventional "terrestrial" computing:

The leasing of IT capability as opposed to ownership. "IT capability" is a very loose term, and its nature varies based on the type of cloud (below). Leasing has several benefits as opposed to ownership - no upfront costs, pay-as-you-go scalability that is easy on startup operations, i.e., practically limitless capacity without having to provision it upfront, etc.

Infrastructure as a Service (IaaS):

Leasing infrastructure (storage, compute power and networking), and owning all applications above it.

Platform as a Service (PaaS):

Leasing infrastructure as well as some application frameworks and common utilities, and owning all applications above it. The frameworks and utilities make it easier to build the applications above.

Software as a Service (SaaS):

Leasing all the application functionality required, and owning nothing.

Virtualisation:

Imagine separating your "mind" from your "brain". We assume exactly one mind per brain and vice-versa. But what if you can have multiple minds within a single brain, a kind of benign schizophrenia? Or more eerily, if a mind can span multiple brains and think more powerful thoughts as a result? That's virtualisation - turning a one-to-one relationship between mind and brain into a many-to-many one.

Cloud computing as opposed to virtualised servers in "terrestrial" computing:

In virtualisation, you still own the brains. In cloud computing, you lease them.

Private cloud:

Leasing brains to yourself to run minds on. This may make sense in certain cases, like with transfer pricing between business units of the same enterprise. But because you haven't rid yourself of the responsibilities of ownership, it may not be as attractive as a public cloud. Nevertheless, it's attractive because sometimes legislation prevents minds from running on strange brains, and you may yourself be testing the concept of mind-brain separation before trusting someone else's brains with the sensitive job of running (and therefore knowing) your minds.