Before we delve into any more code, let\u2019s take a moment to consider the overall design of a database-driven Django Web application. As we mentioned in previous chapters, Django is designed to encourage loose coupling and strict separation between pieces of an application. If you follow this philosophy, it\u2019s easy to make changes to one particular piece of the application without affecting the other pieces. In view functions, for instance, we discussed the importance of separating the business logic from the presentation logic by using a template system. With the database layer, we\u2019re applying that same philosophy to data access logic.<\/p>\n
Those three pieces together \u2014 data access logic, business logic, and presentation logic \u2014 comprise a concept that\u2019s sometimes called the Model-View-Controller<\/em> (MVC) pattern of software architecture. In this pattern, \u201cModel\u201d refers to the data access layer, \u201cView\u201d refers to the part of the system that selects what to display and how to display it, and \u201cController\u201d refers to the part of the system that decides which view to use, depending on user input, accessing the model as needed.<\/p>\n Why the Acronym?<\/strong> The goal of explicitly defining patterns such as MVC is mostly to streamline communication among developers. Instead of having to tell your coworkers, \u201cLet\u2019s make an abstraction of the data access, then let\u2019s have a separate layer that handles data display, and let\u2019s put a layer in the middle that regulates this,\u201d you can take advantage of a shared vocabulary and say, \u201cLet\u2019s use the MVC pattern here.\u201d<\/p>\n Django follows this MVC pattern closely enough that it can be called an MVC framework. Here\u2019s roughly how the M, V, and C break down in Django:<\/p>\n Because the \u201cC\u201d is handled by the framework itself and most of the excitement in Django happens in models, templates, and views, Django has been referred to as an MTV framework<\/em>. In the MTV development pattern,<\/p>\n\n
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