What is the difference between SAAS and Cloud Computing?

There are SAAS vendors (RackSpace Salesforce etc.), Cloud Vendors (Amazon, Microsoft , Google etc). So, what is the difference between the services offered? XaaS, where X is some kind of service, describes a specific Service Model of Cloud Computing. Therefore, an XaaS designates the nature of the service delivered to a client. There are lots of arconyms describing such models, however a vast majority of sources focus on the following three:

• Software as a Service (SaaS)
• Platform as a Service (Paas)
• Infrastructure as a Service (IaaS)

You can also meet the term Hardware as a Service (Haas) which is closely related to #3. The obvious difference between SaaS and the rest, is that SaaS delivers software, and not a platform (for software development) or infrastructure.

It can target the end-users, while PaaS and IaaS usually target developers or organizations that want to use them in order to create Saas (for internal purposes or for delivering software to users).

For more information about Cloud Computing taxonomies, please search for the following papers:

• Cloud Computing Use Case Discussion Group: Cloud Computing Use Cases White Paper v. 4.0

• Bhaskar Prasad Rimal et. al., A Conceptual Approach for Taxonomical Spectrum of Cloud Computing

• Lamia Youseff et. al., Toward a Unified Ontology of Cloud Computing.

The idea of SaaS is that the method of Software development and delivery deviates from the standard model. The Term SaaS existed even before the one of Cloud Computing. It's meaning can be highly confusing as the semantics look similar to plenty of web-service-based terms and architectures(e.g. SOA). Always bear in mind that SaaS describes a Service Model, and not some kind of architecture or methodology. Some good scientific sources about the origins of the term, as well as the evolution of it as a development and business model are the following:

• Keith Bennett et. al., Service-Based Software: The Future for Flexible Software

• Vidyanand Choudhary, Software as a Service: Implications for Investment in Software Development

• Hancheng Liao et. al., An Anatomy to SaaS Business Model Based on Internet.

(Article source: https://stackoverflow.com/questions/5803949/saas-vs-cloud-computing)