What makes it a PaaS not SaaS - or examples

I found some questions here on how to create a SaaS. This much is easy, but what I don't understand is what makes an application a PaaS and not a SaaS. What lines does an application cross before we can start calling it a PaaS (platform as a service) and not just a SaaS (software as a service)? It seems like a small difference but I can't pinpoint it.

I would welcome even examples of PaaS if you can point something about them that makes them a PaaS and not a SaaS. A common name in this area is salesforce but I don't know much about the service itself to understand from it why i开发者_运维问答t's a PaaS.

Edit: I feel that from a programmer's perspective, it's the same job, or no? I think the only difference is the PaaS is for developers as end users and SaaS is for regular users as end users. Does that sum it up?

Using Salesforce.com as an example - they offer the Force.com platform, which provides a database, a programming language, integration features and so on. You can use this platform to build whatever you need/like.

Salesforce also offer their own, prebuilt CRM applications - this is software-as-a-service as the application has been built for you, you simply start using it.

PaaS provides you with the components and tools to build something; SaaS provides you a prebuilt application you can pick up and use straight away. The line can be blurred - again, using the Salesforce example, you can tailor their SaaS offerings by using some of their PaaS technologies.

On the surface it looks pretty simple; Think of Amazon's EC2 or Microsoft's Azure as PaaS and various Services (like a weather serivce) or CMS as SaaS.

PS. Try searching for "PaaS vs. SaaS" on google.

This definition is also pretty common:

• Level 1: IaaS > Virtualization, Server, Storage, Network (AWS, Rackspace …)
• Level 2: PaaS > Runtime, Middleware, OS (Heroku, appfog, dotcloud …)
• Level 3: SaaS > Application, Data (most startups)

Basically, SaaS is a specific online software solution such as CRM, Project Management, Billing, Accounting etc. that mostly flexible by providing some scalability and extensibility features.

On the other hand, PaaS is kind of base services that contains required features to host many different type of online softwares including SaaS applications.

At this point i can say that there are different kind of PaaS in the market. Some of them are targeting the developer by providing infrastructures and frameworks in specific technologies such as Microsoft Azure, Google Apps, Heroku and more ...

The others (including Force.com and Viravis) provides complete solution for a specific needs (such as online database applications) for developers and business analysts as well as the end users by providing required tools to develop online applications without programming.

As a result, all of the PaaS providers in the market presents a simlified solution for creating and running online softwares including SaaS applications. I think this is the main difference between SaaS and PaaS.

Check this Question for other opinions.

I think this is how it is -

IaaS - Like having a computer with or without an OS/operating system. Think brand new computer with or without Windows OS.

PaaS - Like having a computer with an OS, and tools/software to make your own tools/software or apps.
Think computer where you are allowed to touch only things like an installed database, IDE, web server etc.

SaaS - Like having a computer with a pre-loaded software/tool. You can tweak the pre-loaded tool as per your needs, but you don't get to make your own tools. Think computer where you are allowed to use only excel spreadsheets. You can change the font size and stuff, but you are pretty much stuck with excels features. If you wanted to make a software like excel yourself, you need PaaS or even IaaS.

Real world examples -

IaaS - Rackspace, Amazon Ec2 etc.

PaaS - Heroku, Google App Engine

SaaS - SalesForce, Workday

PAAS (Platform As A Service) :

• A layer on top of IAAS (Infrastructure As A Service)
• Examples: Runtimes (like java runtimes), Databases (like mySql, Oracle), Web Servers (tomcat etc)

SAAS (Software As A Service) :

• A layer on top on PAAS
• Examples: Applications like email (Gmail, Yahoo mail etc), Social Networking sites (Facebook etc)

source

When you develop an application and deploy it on server(Example: www.gmail.com), then many user comes and start using your application. Your application will be SaaS for the users who are using your application.

When you have developed an application and want a server(Pre configured server like having linux, java, hibernate, mysql etc.) that can run your application. Application that provides you that pre configured server will be PaaS for you.