Model meaning in MVC

Question

Why is MODEL in ASP.NET MVC sometimes used as part of an application that talks to a database like here and sometimes as a business object that "travels" across applications delivering data like here?

Answer 1

MVC has evolved in different directions since its Smalltalk beginnings to the point where it is often used to describe very disparate architectures, as you've discovered.

Martin Fowler blogs about the evolution of MVC here. http://martinfowler.com/eaaDev/uiArchs.html

There is an explanation of the differences between MVC, MVP and MVVM here: http://joel.inpointform.net/software-development/mvvm-vs-mvp-vs-mvc-the-differences-explained/

My 10c:

Many examples of ASP.NET MVC 3 are more closely aligned to the MVVM pattern than MVC. In MVVM, ViewModels are tailored for the data specifics of each View (i.e. 'ViewModels' are not merely domain models, but are decorated with View / Presentation Tier concerns such as validation rules, field prompts / names, field visibility etc).

(Back to MVC) In smaller data centric projects without much need for back end tiering, M can be as simple as an ORM model (e.g. an .EDMX with some autogenerated POCOs) with a few rules. In this case MVC could just about be regarded as an application architecture.

But in larger projects using MVC, the original (Smalltalk) 'M' of model is now split up into several other layers, e.g. domain entities, service facades, Service (e.g. SOA), Business, and Data Tiers, etc (so here, M VC is a presentation tier pattern, and M is the rest of your system). So for example in such a project, the 'Models' folder of your MVC project could simply be proxied service references and proxied domain entities used to communicate with the 'back end' of your system, or even an abstraction of this communication (e.g. see the service agent / service facades used in the Composite Application Block).