To quote from the article:
"In meeting these significant challenges, DISA has actively leveraged the fact that these requirements have parallels in the general information technology industry. This fact has led to the rapid adoption and implementation of many commercial solutions. Service oriented architecture (SOA), hardware virtualization, and grid computing are just a few of these. The latest of these adoptions seems to be Cloud Computing.
First coined by Sun Microsystems’s John Gage over twenty years ago Cloud Computing is now taken hold as the “next step in the Internet’s evolution.  This concept, however, is more than just the provisioning of computing resources (i.e. hardware, software, storage, services, etc.). The basic provisioning of infrastructure is the typical description of grid computing. Cloud computing is more in that it relates to the underlying architecture in which the application services are designed. The application not only runs in the cloud, but the cloud allows for the development, deployment, capacity growth, performance and reliability of the application as well.
When fully employed, cloud computing infrastructures, the middleware and the application platforms, should have the following characteristics:
- Self-healing: In case of failure, there will be a hot backup instance of the application ready to take over without disruption (known as failover). It also means that if a failure causes the backup to become primary, the system will automatically launch a new backup to maintain required reliability policies.
- SLA-driven: The system is dynamically managed by service-level agreements so that if the system is experiencing peaks in load, it will create additional instances of the application on more servers in order to comply with the committed service levels — even at the expense of a low-priority application.
- Multi-tenancy: The system is built to allow the sharing of infrastructure, without the customers being aware of it and without compromising the privacy and security of each customer’s data.
- Service-oriented: The system allows for the composing of applications out of discrete services that are loosely coupled and independent of each other (mash-ups). It also provides for reuse of services and prevents the changes or failure of one service to disrupt others.
- Virtualized: Applications are decoupled from the underlying hardware. Multiple applications can run on one computer (i.e. VMware) or multiple computers can be used to run one application (grid computing).
- Linearly Scalable: The system will be predictable and efficient in growing the application.
- Data Management: The distribution, partitioning, security and synchronization of the system’s underlying data is actively managed"