電端運算（Cloud Computing）何其多？

資料來源：
乒乓王 Blog
David Akka Blog

SaaS - Software-as-a-Service is a model of software deployment whereby a provider licenses an application to customers for use as a service on demand. One example of SaaS is the Salesforce.com CRM application.
IaaS - Infrastructure-as-a-Service is the delivery of computer infrastructure (typically a platform virtualization environment) as a service. Rather than purchasing servers, software, data center space or network equipment, clients instead buy those resources as a fully outsourced service. One such example of this is the Amazon web services.
PaaS - Platform-as a-Service is the delivery of a computing platform and solution stack as a service. It facilitates the deployment of applications without the cost and complexity of buying and managing the underlying hardware and software layers. PaaS provides the facilities required to support the complete lifecycle of building and delivering web applications and services. An example of this would the GoogleApps.
DaaS - Desktop-as-a-Service enables users to use their desktops virtually from anywhere. Commonly known as "Desktop Virtualization", this concept separates personal computer desktop environments from the physical machine through a client-server computing model. Nowadays, with the rise of SaaS and RIA (Rich Internet Applications) this method of usage is becoming obsolete.