Concurrent Models in Software Engineering: Types & Applications

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  • 0:04 Concurrent Models in Software
  • 0:39 The Waterfall Model
  • 2:25 The Prototype Model
  • 3:47 The Spiral Model
  • 5:02 Lesson Summary
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Lesson Transcript
Instructor: Meghalee Goswami

Meghalee has a masters of computer science and communication engineering.

This article provides information on the topic concurrent models in software engineering, along with models like the waterfall model, spiral model, and prototype model, and discusses their advantages, disadvantages, and applications.

Concurrent Models in Software

Most of the successful software out there involves a series of phases of development, such as requirements gathering and prototyping, that are put together to develop the software. These phases are discrete and often performed concurrently. Often there is an intertwining between the phases, which makes it inevitable to return to the earlier phases to make some changes according to the results obtained in the later phases. This type of a model, in which multiple phases are performed concurrently, can be coined as a concurrent model. Some examples of concurrent models in software engineering will be discussed in this lesson.

The Waterfall Model

In the waterfall model, the development of the software works linearly and sequentially. This model is also called the classical waterfall model. The waterfall model is one well-known version of the software development life cycle for software engineering. The development phases are linear and sequential, which signifies its nature. Once water begins its journey down a mountain, it can't return back. It's the same with the waterfall model. Once a phase of development is completed, the process proceeds to the next phase, and there is no turning back.

This model was introduced by Winston W. Royce in 1970. The following model shows a waterfall model. As you can see:

Waterfall model
Waterfall model

So, as you can see, the waterfall model is popular for its simplicity. However, the waterfall model also has its own share of perks and cons.


  • It's relatively simple to understand.
  • It's a sequential model. Each phase is followed by the next in sequential order. In any phase, if you want to return back some earlier phase then you would have to go through the entire process again sequentially.
  • It needs very few resources.
  • There is no scope of phase overlap here, since you can't proceed to the next phase until you finish the earlier phase.


  • It's not very flexible.
  • It takes a lot more time.
  • No backtracking is allowed.
  • Any revision is prohibited.
  • It's difficult to estimate time and cost.

The waterfall model is best suited for a less uncertain situation wherein you would need to plan out everything well in advance (for example, constructing a building).

The Prototype Model

The prototype model suggests that, before carrying out the development of actual software, a working prototype of the software should be built. A quick design is carried out and a prototype is built, after which the developed prototype is submitted to the customer for evaluation. Based on customers' feedback and requirements, the prototype is refined and modified. This process continues until the customer approves the prototype. The actual system is then developed using an iterative waterfall model. The finished software has more functioning capabilities, is more reliable, and gives better performance compared to the prototype model.

The prototype model has its share of advantages and disadvantages.


  • There's strong communication between users and developers.
  • That anything missing can be detected, since it's comparatively easier to see the user interface, track, and then decide.
  • The model is flexible.
  • There's a scope of innovation, because there are so many possible things that you could do with a user interface. There's always a scope of improvement and innovation.


  • The problem of incomplete analysis exists.
  • It's time-consuming.
  • It isn't cost effective.
  • Its requirements change frequently.

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