Charateristics and features of every software framework_问答_开发者

I was trying to find an answer for my question today using google and StackOverflow search engines... but no luck :)

I was wondering what are the key features of every framework for end user, and how can you characterize every framework from the end-user point of view (I've looked into Framework Design Guidelines by K. Cwalina, but I've found only concepts and guidelines for framework architect开发者_JAVA百科s), for me:

it should be extensible
should let build extensible and reusable components
and of course : Simple things should be simple, complex things should be possible. (http://en.wikiquote.org/wiki/Alan_Kay)

I think there is much more out there.

Please share your knowledge.

Here are two good quotes from Ralph Johnson and Brian Foote

A framework is a reusable, ``semi-complete'' application that can be specialized to produce custom applications

One important characteristic of a framework is that the methods defined by the user to tailor the framework will often be called from within the framework itself, rather than from the user's application code. The framework often plays the role of the main program in coordinating and sequencing application activity. This inversion of control gives frameworks the power to serve as extensible skeletons. The methods supplied by the user tailor the generic algorithms defined in the framework for a particular application.

There was a special issue of CACM that you might want to take a look at too.

Here's one more link The Hollywood Principal. "Don't call us, we'll call you." About how the framework inverts the typical control so the framework calls your code instead of you calling some library code.

It sounds like you just want to know what is the defining characteristic of a framework...?

From FOLDOC:

In object-oriented systems, a set of classes that embodies an abstract design for solutions to a number of related problems.

So basically, a class library ("set of classes") that's extensible ("embodies an abstract design"),

I'll attempt a definition based on my own understanding: A framework is a body of code that abstracts a subset of tasks common to some classes of application programs. The intent is to provide, once, proven and tested code so that application programming doesn't have to keep re-inventing code for the common tasks handled by the framework.

In real life, frameworks often spring into being when a programmer or team get carried away with generalizing and future-proofing what started out as a single application. There's an honorable intent to start code re-use, but it often turns out that such frameworks aren't designed with intent from the beginning, don't have consistent design reflecting this intent, and are actually lousy code that ends up not being re-used at all. Most architects who feel qualified to create frameworks, aren't.

The difference between libraries and frameworks: You call libraries. Frameworks call you.

Answering your question covering the depth it deserves is beyond the scope of this forum. All you should do is read this book though its focused on .Net frmaework specifically and written by the designers of the .Net framework, I'm sure the wisdom and information that this book provides would be sufficient to answer your question and satisfy your curiosities on the subject.

Framework Design Guidelines: Conventions, Idioms, and Patterns for Reusable .NET Libraries (2nd Edition)

alt text http://www.lybrary.com/images/0321605012.jpg

A Framework is for me a other name for a Library (like Boost and many others) that is not about only one Topic (there are Librarys about Math, Networking, whatever out there, but these are no Frameworks) and it is of course Extensible and you can combine the Features of it to do your Job.