Cleaning Up a SaaS Terminology Mess
The concept of Software as a Service (SaaS) can be confusing, not least because different vendors, users, and commentators will describe SaaS products with many different terms. These include cloud computing, ASP, hosted services, services on demand, software plus service, multi-tenant applications, and utility computing, in addition to SaaS. These terms in fact have slightly different meanings, and the differences are quite significant. Therefore, it makes sense to clearly delineate the definition of each of these terms, so that users will know exactly which services they require.
Software as a Service : Software as a Service (SaaS), a model of software distribution in which applications are licensed to clients as a service on demand by providers, is just as much a business model as it is a technology. By definition, SaaS is typically associated by business associates and professionals with business software. It is typically held as a low-cost method for businesses to secure software rights as needed versus licensing every device with all applications. This on demand licensing allows the benefits of commercially licensed utilization without the associated complexity and possibly large cost of providing all devices with applications only used when needed. SaaS vendors may either host this application on their own servers, or download the application to a consumer device, then disabling it after finished using it, or after the on-demand contract expires.
Multi-tenancy: Multi-tenancy is an architectural software principle where the software runs on a software-as-a-service (Saas) vendor’s servers, while serving multiple client organizations, or tenants. Multi-tenancy allows many clients to co-exist securely on one infrastructure. SaaS’s applications architecture and design are built specifically with a "multi-tenant’ backend, which enables access by several customers or users to a shared data model, differentiating SaaS from client/server of ‘ASP’ (Application Service Provider) solutions. This is because Saas providers influence massive economies of scale in support, deployment, and management.
Application Service Provider: A business providing computer-based services to clients over a network is known as an Application Service Provider (ASP). In general, most applications supported by ASP were massive client-server programs with basic HTML Web interfaces. An ASP placed programs of your choice on their site’s server, but might not have possessed multi-tenant capability. The ASP model concentrates on providing organizations with the capacity to move specific application processing tasks to a server managed by a third party. Most ASPs did not consist of enough application and business domain expertise concerning applications they run.
“Hosted” : Hosted is an ambiguous term either meaning SaaS or ASP. A Hosted Service Provider (xSP) is a business bearing a combination of conventional IT functions such as Web development, infrastructure, email, applications (Software as a Service), monitoring, security, storage, and website hosting, over the Internet of other wide area networks (WANs). An xSP fuses the abilities of an Internet service provider (ISP) and an application service provider (ASP).
“On-Demand”: This software is not conventionally purchased but is rented as per the user’s requirements. It may or may not be hosted on a remote server and can also be multi-tenanted. On-Demand Computing is also called Utility Computing, wherein the grouping of computing and storage capabilities is utilized on a pay-as-you-use basis (just like water, gas, electricity or telephone utilities)
Software plus Services : The term "Software plus Services" is used to describe the idea of using locally running applications and hosted services in tandem, to get the greatest benefits from both architectures. Combined applications are generated by using remote services and traditional software installations. The resulting applications should allow users to employ the software from any device in any form that they need. The Software plus Services model allows for Software as a Service (SaaS) to be added to regular software suites running on servers and clients. This will allow a software vendor to benefit from the developing model of cloud computing while still employing the more traditional model of individual software installations, so that users can run their applications from any PC or any device that they have available.
Cloud Computing: The cloud computing model involves rapidly scalable computer resources provided to clients as a service through the World Wide Web. These resources are often virtualized. Users of the cloud do not need to control the technological infrastructure or know how it operates. There are three basic concepts that are usually part of cloud computing architecture, namely infrastructure as a service (IaaS), software as a service (SaaS), and platform as a service (PaaS)