Software as a Service (SaaS) is a cloud deployment model that provides users with access to software applications over the internet, without requiring them to install, maintain, or update the software on their own devices. SaaS is primarily focused on the application layer, as it delivers the complete functionality of the software to the end users, while abstracting away the underlying infrastructure, platform, and middleware layers. SaaS providers are responsible for managing the servers, databases, networks, security, and scalability of the software, as well as ensuring its availability, performance, and compliance. SaaS users only pay for the software usage, usually on a subscription or pay-per-use basis, and can access the software from any device and location, as long as they have an internet connection. Some examples of SaaS applications are Gmail, Salesforce, Dropbox, and Netflix. References:
* Shared Assessments CTPRP Study Guide, page 15, section 2.2.2
* Cloud Computing Deployment Models and Architectures, section on Cloud Computing Models
* Layered Architecture of Cloud, section on Application Layer