Glossary

This glossary includes terms that are useful for understanding the different options available when deploying enterprise applications. It only provides brief description of the most common terms. Some of the descriptions are partially or completely reproduced from Wikipedia and/or other public information sources.

API
An Application Programming Interface (API) is an interface that a software program implements in order to allow other software to interact with it, much in the same way that software might implement a user interface in order to allow humans to interact with it.

Cloud API
The Cloud Servers API launched on 2009-07-14 under the Creative Commons Atribution 3.0 license allows clients to create, configure and control virtual servers. In addition to issuing basic management commands, it "enables elastic scenarios" whereby servers are instantiated and destroyed in response to fluctuating load (one of the key characteristics of cloud computing).

Cloud Computing
Cloud computing combines virtualization with other technologies to provide dynamic scalability and agility. Application images can run on private clouds (on premises), on public clouds (off premises) or both (hybrid clouds). The concept generally incorporates combinations of the following:

• Infrastructure as a service (IaaS)
• Platform as a service (PaaS)
• Software as a service (SaaS)

Cloud OS
Refers to an Internet-based operating system where the only software you need to access the cloud is a browser.

Elastic Computing
The ability to manage, measure, predict and adapt responsiveness of an application based on real-time demands placed on an infrastructure, using a combination of local and remote computing resources.

Grid Computing
Grid computing is the combination of computer resources from multiple administrative domains applied to a common task, usually to a scientific, technical or business problem that requires a great number of computer processing cycles or the need to process large amounts of data.

Guest OS
The operating system installed inside a virtual machine (or a partition). In a virtualization solution the guest OS can be completely different from the host OS.

Hardware Appliance
Generally a separate and discrete hardware component specifically designed to provide a specific computing resource.

Host OS
The operating system hosting one or more virtual machines (or partitions) and sharing physical resources with them. It's where the virtualization product or the partitioning product is installed.

Hybrid Cloud
A computing environment that combines both private and public cloud computing environments.

Hypervisor
A hypervisor, also called virtual machine monitor (VMM), is a computer software/hardware platform virtualization software that allows multiple operating systems to run on a host computer concurrently.

IaaS
Infrastructure as a Service (IaaS) is the delivery of computer infrastructure (typically a platform virtualization environment) as a service.

Interoperability
The term is used to describe the capability of different programs to exchange data via a common set of exchange formats, to read and write the same file formats, and to use the same protocols.

Mashups
It is a web page or application that combines data or functionality from two or more external sources to create a new service

Middleware
Middleware sits "in the middle" between application software that may be working on different operating systems. Multi-tenant
Refers to a principle in software architecture where a single instance of the software runs on a server, serving multiple client organizations (tenants).

On Premises
On-premises software is installed and run on computers on the premises (in the building) of the person or organisation using the software, rather than at a remote facility, such as at a server farm somewhere on the internet.

On Demand
Frequently refers to Software as a Service (SaaS).

PaaS
Platform as a service (PaaS) is the delivery of a computing platform and solution stack as a service. It facilitates deployment of applications without the cost and complexity of buying and managing the underlying hardware and software layers

Pay as you Go
A way to pay application services as they are being used. Typically used for On Demand software while On Premises software mainly uses the more traditional licensing model.

Public Cloud
A cloud computing environment that is open for use to the general public.

Private Cloud
An internal cloud laying behind the organization’s firewall.

SaaS
Software as a Service (SaaS) refers to a model of software deployment whereby a provider proposes an application for use as a service on demand.

Service Oriented Architecture (SOA)
It provides a set of principles or governing concepts used during phases of systems development and integration.

Utility Computing
Utility computing is the packaging of computing resources, such as computation and storage, as a metered service similar to a traditional public utility (such as electricity, water, natural gas, or telephone network).

Virtualization
A software technology allowing an operating system to run unmodified on an isolated virtual environment, called virtual machine, where a platform's physical characteristics and behaviours are reproduced.

Virtual Machine
An empty, isolated, virtual environment, lying on top of a host OS, equipped with virtual hardware (processor, memory, disks, network interfaces, etc) and managed by a virtualization product. It's where the guest OS is installed.

Virtual Appliance
A virtual appliance is a virtual machine image designed to run on a virtualization platform (e.g. VMware Workstation, Xen, VirtualBox).

Web Services
A web service can be defined as "a software system designed to support interoperable machine-to-machine interaction over a network.

Web 2.0
The term "Web 2.0" is commonly associated with web applications which facilitate interactive information sharing, interoperability, user-centered design and collaboration on the World Wide Web.

XaaS
Commonly refers to "everything as a service". It includes today Infrastructure as a Service, Software as a Service, Platform as a Service.