IaaS, SaaS and PaaS are the obvious as-a-service offerings, but there are plenty of others. In fact, just about every letter of the alphabet has an "as a service."
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Access as a service
AaaS can also mean authentication as a service, which also refers to cloud security, and a single- or two-factor authentication system to access cloud data.
Backup as a service
Compute as a service
AT&T offers compute as a service, meaning computing capacity on an as-needed basis for enterprises.
Database as a service
Forrester noted the term in a 2008 report.
It can also mean desktop as a service, which Dell offers.
Email as a service
Also known as webmail, of course, the federal government experimented with using the term.
EaaS can also refer everything as a service, which is how HP describes its cloud strategy.
Firewall as a service
Coined to describe cloud security, as the Trend Cloud Security blog explains.
Google platform as a service
ZDNet has a reference guide for the difference between the Google PaaS and Amazon's model.
Hardware as a service
Infrastructure as a service
A variety of providers use the term IaaS.
Java platform as a service
A type of application development, as IBM describes here.
Knowledge as a service
Log on as a service
Management as a service
Management as a service can take many forms, including cloud security, as described by Verizon.
Also, you might see marketing as a service, which is just that, explains the CRM Search blog.
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Network as a service
Open platform as a service
Platform as a service
Used to describe a cloud-based application development and testing model.
Query as a Web service
A product by SAP used by business enterprises.
Robot as a service
RaaS is a term used by Intel in a white paper to describe service-oriented robotics computing.
Software as a service
A widely used term to describe cloud-based software that is accessed via the network.
Testing as a service
HP offers testing as a service for application developers to test their research.
User interface as a service
Salesforce.com announced in 2007 its user interface as a service model, which it describes here.
Video surveillance as a service
Video surveillance as a service is an emerging trend in the SaaS market, as a CSO report explains.
Website as a service
X as a service
As the blog SearchCloudComputing.com describes it, XaaS means anything as a service.
You as a service
As this study points out, a variety of cloud-based initiatives can be classified as you as a service.
Zebra as a service
Not yet an enterprise IT term, sales firm Selling to Zebras is attempting to make it one.
(Note: This list is not meant to be all-inclusive; if you have suggested additions to the list, send them to BButler@nww.com.)