The cloud - some definitions

Over the last week I have been talking to quite a few people about the cloud and the potential ramifications. There seem to be a lot of issues and quite a few services out there. And there is a lot of buzz, marketing etc so sometimes it is hard to say what is what. Thus I decided to write down some definitions, just to make things clearer (hope it will help someone).

 Let's try to group the different aspects of the cloud somewhat (from Wikipedia):

1. Software as a Service (SaaS) - It is simply the delivery of a software over the internet.
2. Platform as a Service (PaaS) - The delivery of a computing platform
3. Infrastructure as a Service (IaaS) - The delivery of computer infrastructure

So now let's look at a few examples:

SaaS - Google Apps (including Google Docs), Microsoft Office 365

PaaS - Google Apps Engine, Microsoft Azure AppFabric

IaaS - Amazon Elastic Compute Cloud (EC2), Windows Azure

To access the cloud the user need a client. Normally this is naturally a PC or Mac or Linux or… But there are more options out there. The most notable would be the iPad (and derivatives) and ChromeOS. The last is admittedly not a device, but points in an interesting direction. In a cloud based future the device the end user use to interact with cloud services needs a few distinct characteristics: Ease of use, connectivity (to the Internet), Fast storage (for offline storage) and Graphics (to be able to show video, games etc) and sound plus video camera/camera (for online communication) .

So the stack would be (from the user), the client, IaaS, PaaS, SaaS. Ie you can build a SaaS on top of a PaaS which use IaaS to operate. You can naturally also build a SaaS on top of IaaS. And sometimes connect your client directly to a IaaS (like file storage).

With these definitions you might want to argue that the cloud is not something new? And yes, in some aspects it is not something new. The example of a mainframe from the 70's deliver software over the internet. We had Application Software Provider (ASP) in the 90's, it is basically the same thing as SaaS but it took some time (and a new acronym) before it caught on.

But the paradigm shift is in the ease of use, the massive (and growing) amount of services, the  hype, the scalability and the cost. Most notable is the scalability, a good cloud services allows a lot of users to use the same solution (in a multi tenancy environment).