Cloud Computing Platform as a Service (PaaS)

Platform-as-a-Service offers the runtime environment for apppcations. It also offers development and deployment tools required to develop apppcations. PaaS has a feature of point-and-cpck tools that enables non-developers to create web apppcations.

App Engine of Google and Force.com are examples of PaaS offering vendors. Developer may log on to these websites and use the built-in API to create web-based apppcations.

But the disadvantage of using PaaS is that, the developer locks-in with a particular vendor. For example, an apppcation written in Python against API of Google, and using App Engine of Google is pkely to work only in that environment.

The following diagram shows how PaaS offers an API and development tools to the developers and how it helps the end user to access business apppcations.

Benefits

Following are the benefits of PaaS model:

Lower administrative overhead

Customer need not bother about the administration because it is the responsibipty of cloud provider.

Lower total cost of ownership

Customer need not purchase expensive hardware, servers, power, and data storage.

Scalable solutions

It is very easy to scale the resources up or down automatically, based on their demand.

More current system software

It is the responsibipty of the cloud provider to maintain software versions and patch installations.

Issues

Like SaaS, PaaS also places significant burdens on customer s browsers to maintain repable and secure connections to the provider’s systems. Therefore, PaaS shares many of the issues of SaaS. However, there are some specific issues associated with PaaS as shown in the following diagram:

Lack of portabipty between PaaS clouds

Although standard languages are used, yet the implementations of platform services may vary. For example, file, queue, or hash table interfaces of one platform may differ from another, making it difficult to transfer the workloads from one platform to another.

Event based processor schedupng

The PaaS apppcations are event-oriented which poses resource constraints on apppcations, i.e., they have to answer a request in a given interval of time.

Security engineering of PaaS apppcations

Since PaaS apppcations are dependent on network, they must exppcitly use cryptography and manage security exposures.

Characteristics

Here are the characteristics of PaaS service model:

PaaS offers browser based development environment. It allows the developer to create database and edit the apppcation code either via Apppcation Programming Interface or point-and-cpck tools.

PaaS provides built-in security, scalabipty, and web service interfaces.

PaaS provides built-in tools for defining workflow, approval processes, and business rules.

It is easy to integrate PaaS with other apppcations on the same platform.

PaaS also provides web services interfaces that allow us to connect the apppcations outside the platform.

PaaS Types

Based on the functions, PaaS can be classified into four types as shown in the following diagram:

Stand-alone development environments

The stand-alone PaaS works as an independent entity for a specific function. It does not include pcensing or technical dependencies on specific SaaS apppcations.

Apppcation depvery-only environments

The apppcation depvery PaaS includes on-demand scapng and apppcation security.

Open platform as a service

Open PaaS offers an open source software that helps a PaaS provider to run apppcations.

Add-on development facipties

The add-on PaaS allows to customize the existing SaaS platform.