Question

Compare and contrast a web service and an SaaS solution within the context of cloud computing

Answer 1

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First, "web service" is not about offering "web site file maintenance," and it is not about offering one or more host services or not. In particular, a web service is an API that typically provides information for consuming apps. A typical "web site" or "web application," on the other hand, is something to be consumed by end customers (humans). For instance, google mail is a web application, whereas a web service is the Yahoo Weather API.

A web service could be deployed on a single physical host, a load-balanced cluster of multiple physical hosts, on a single virtual host, or a load-balanced cluster of virtual hosts. However, just because it is deployed on someone's "cloud infrastructure" (eg multiple virtual hosts) does not make it a "cloud service."

The term "SAAS" is mostly a marketing term that can mean two different things. Either an application/service that provides "cloud features," for example, Dropbox; or, a service that infrastructure providers deliver, typically consisting of virtual machine hosting / app containers and software defined networking, like AWS.

SaaS is only a software delivery technique. Think about it this way: You are a software provider and you need to provide software applications that you want to use to your customers. But you're not selling them a DVD and saying, "Here! Go install and use this on your servers." Instead, you are hosting the application on your own servers and providing customers with access to it over the internet for a subscription fee. It is outsourcing of apps (e.g. email, implementation of human resources, accounting, taxes, etc.).

When we're talking about SaaS, we're talking about fully functional standalone apps that provide some company service.

SOA is a comparable thing, but at a lesser level. It does not provide company service, but rather offers as a service tiny, isolated procedures.

SOA is a software construction architecture style. The concept is to construct your application by creating a collection of stateless, reusable, decoupled network services (e.g. web services) (or interacting with them).

Ref: service-architecture.com by Douglas K Barry

SOA is a software construction architecture style. The concept is to construct your application by creating a collection of stateless, reusable, decoupled network services (e.g. web services) (or interacting with them).

I believe that the word "service" is what confuses individuals. SaaS and SOA are both providing "services." But the goal is distinct: SOA provides services to other apps as opposed to SaaS, which provides customers with services.

You can use SOA to construct your SaaS application, of course. With SaaS, you provide services to more customers and having it constructed on top of an SOA architecture makes it simpler to scale the application than a more monolithic "do it all" application. In short, a web service is an API ; a SAAS is an infrastructure / platform with services.