Video 4: Design Patterns

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Web Application Development: Basic Concepts

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University of New Mexico

Web Application Development: Basic Concepts

124 notes

This is the first course in a Coursera Specialization track involving Web Application Architectures. This course will give you the basic background, terminology and fundamental concepts that you need to understand in order to build modern full stack web applications. A full stack web developer is familiar with each "layer" of the software technologies involved in a web application, including data modeling and database technologies, the web server environment and middleware components, network protocols, the user interface and basic visual design and user interaction concepts. In this course we will learn by doing. We will start by learning the major components of web application architectures, along with the fundamental design patterns and philosophies that are used to organize them. You will build and continually refine a fully functional full-stack web application as we progress through the modules in this course. Along the way you will be exposed to agile software development practices, numerous tools that software engineers are expected to know how to use, and a modern web application development framework. This course is also available in Spanish. To join the Spanish version, visit this page: https://www.coursera.org/learn/apliweb.

À partir de la leçon

Module #1 - Web Applications in Context

This module sets the context for what we will study in this specialization by first providing a historical perspective on computing and web applications. Next we provide an overview of how the Internet works, and then we discuss how web applications have evolved over the past few decades. After that we’ll discuss some of the elements of modern software practice, including the typical tools that software engineers now use and the agile development practices they follow. The notion of software design patterns will introduced, and the n-tier architecture design pattern, fundamental to modern web application design, is then presented. Will also discuss a few current topics related to web application development. Finally, we will show you how to set up the software development environment you will use throughout the remainder of the courses in this.

What is a Web Application? - An Overview0:33

Video 1: Web Apps - A Model2:47

Video 2: Web App Definition5:14

Video 3: Evolution of Web Apps8:51

Video 4: Design Patterns4:58

Video 5: n-Tier Architecture6:20

Rencontrer les enseignants

Greg Heileman
Professor and Associate Provost
Electrical and Computer Engineering
Manel Martínez-Ramón
Professor
Electrical and Computer Engineering

[MUSIC]

Let's discuss some of the design tools that software engineers use.

We've already seen that modern web applications involve a significant

amount of complexity, particularly on the server side.

But even what is happening on the client side, in the browser,

is getting a lot more complicated over time.

A typical web application involves numerous protocols,

programming languages and technology spread throughout the web stack.

And this makes developing, maintaining, and

extending complex web applications extremely difficult.

Thus, we need to use a foundation of solid design principles

in order to simplify the development and maintenance of web applications.

Now, software engineers use abstraction to manage complexity.

You can't keep all of the details associated with

a large software system in your head.

There's just too much complexity.

If you try to, you're likely to make mistakes.

The human mind can only handle so much complexity, so we use abstraction.

Abstraction involves representing the essential features of a software design or

component, without including the background details.

In other words by representing only the most important elements of a design

you're said to be abstracting away the complexity.

Design patterns provide useful abstractions for

building software systems.

Some of the most important design abstractions used by software engineers

are design patterns.

What is a design pattern?

It is a reusable solution to a design problem that

involves a set of components that interact in order to solve a general

design problem within a particular context.

Let's take a look at this definition.

So a design pattern is a reusable solution involving interacting software components.

In other words, the design patterns specifies how you should

organize these components In order to solve the design problem.

These are often software components that could be at a fairly high level or they

could be all the way down at the level of an object in an object oriented system.

Now the term context used in this definition describes the specific

circumstances under which you are trying to apply this design pattern,

in other words the individual motivating factors or

problems that need to be resolved in order to build this successful software system.

We'll talk more about this in just a moment.

So design patterns are simply abstract templates that can be applied over and

over again in many different contexts.

It's important to understand that design patterns are not actual code.

They're design ideas that just commonly occur.

In other words, they occur enough that we give them a name.

And there are many different ways to implement a given design pattern in code.

So why should we do this?

Well-known design patterns are often used, alone or

in combination, to simplify complex designs.

And the other thing is, design patterns provide us a way to communicate with

one another about the particular parts of a design.

What this means is that design patterns are the vernacular that

software engineers use to communicate with one another about designs.

Here's an example.

The client server model that we've already discussed,

it's an architectural design pattern.

Let's look at its features.

It's a reusable template that can be applied over and over again.

In our case, we have applied it to the problem of communicating

over the internet while using the World Wide Web, that's our context.

The whole point of the client server architecture is to distribute

the components of an application between the client and the server in some way.

What gets put where determines the particular type

of client server architecture.

For example you might be trying to share a database amongst a bunch of users, or

files, or a printer.

This is a very common scenario or

context in which you would use the client server architecture.

In our case, we're distributing the browser to the client and

the web server to the server.

And what we have here are interacting components, right?

There's the browser interacting with the web server.

And when I've now used the term client-server,

you immediately have an idea of what is meant, what is involved by this design.

So we're already using design patterns to communicate with one another.

Now in order to build complex web applications, we're going to have to make

use of numerous design patterns throughout this course.

That will help us organize how pieces are placed

within a web application architecture.

We'll start by elaborating the client-server design pattern in more

detail in the next video.

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