Implementation Of Softwares

One of the companies that sells that kind of service classifies SaaS into four "maturity levels," whose key attributes are configurability, multi-tenant efficiency, and scalability.Each level is distinguished from the previous one by the addition of one of those three attributes:
Level 1 - Ad-hoc/custom: Each customer has a customized version of the hosted application that runs as its own instance on the host's servers. Migrating a traditional non-networked or client–server application to this level of SaaS typically requires the least development effort, and reduces operating costs by consolidating server hardware and administration.
Level 2 - Configurable: This adds greater program flexibility through configurable metadata, so many customers use separate instances of the same application code. This lets the vendor meet different customer needs through detailed configuration options, while simplifying common code base maintenance and updating.
Level 3 - Configurable, multi-tenant-efficient: This adds multi-tenancy to the second level, so a single program instance serves all customers. This enables more efficient server resource use without apparent difference to the end user, but ultimately faces scalability limits.
Level 4 - Scalable, configurable, multi-tenant-efficient: The fourth and final SaaS maturity level adds scalability through a multitier architecture that supports a load-balanced farm of identical application instances that run on a variable number of servers. The provider can adjust system capacity to match demand by adding or removing servers without further altering the software architecture.
SaaS architectures may also use virtualization, either in addition to multi-tenancy, or in place of it. A principal virtualization benefit is that it can increase system capacity without additional programming. On the other hand, much programming may be required to construct a more efficient multi-tenant application. Combining multi-tenancy and virtualization provides still greater flexibility to tune the system for optimal performance. In addition to full operating system-level virtualization, other virtualization techniques applied to SaaS include application virtualization and virtual appliances.
SaaS application development may use various types of software components and frameworks. These tools can reduce time-to-market and the cost of converting a traditional on-premise software product or building and deploying a new SaaS solution. Examples include components for subscription management, grid computing software, web application frameworks, and complete SaaS platform products