Software-as-a-Service (SaaS) is more than simply an application-hosting model. It is an integrated service that involves implementation, hosting, and ongoing maintenance services. In addition, the technical architecture of the SaaS model constrains clients' options for customizing the application at the core level of the application (e.g., changes in data schema). Customers also have less control over the changes that are made to the application by the vendor throughout its lifecycle.