The "Flex Framework" is a collection of AS3 classes and components used in developing RIAs.
"Flex Builder" is an IDE used to develop "Flex Applications."
Much in the same way HTML is a collection of tags to develop web pages and Dreamweaver is an IDE for developing web pages. However you don't need Dreamweaver, you can use Notepad, BBEdit, etc. as well.
If you use something other than Flex Builder to develop in Flex, you need to download the Flex SDK to compile. The end result of a compiled Flex Application is an SWF file (Same as Flash).
With the compiled SWF file, a user only needs to have Flash Player installed to run the application.
Most Flex apps are developed, deployed to a server and then a web browser is used to serve the application to the user for use.
I haven't used AIR yet so I don't know what the end product of a compliled AIR Application is, but AIR is an alternative delivery system for Flex Applications, replacing the web server and browser so to speak. It's primary purpose is for deploying RIAs to a user's desktop, independant of an internet connection.
AIR, also allows for the use of HTML, AJAX etc. So an AIR Application could be a collection of all these things, compiled together.
To run an AIR Application, you need AIR Runtime installed on your computer.
Best Answer
You could use a class that acts as a proxy for the original ArrayCollection and the data stored in it. You can set the filter function on the proxy and have the proxy delegate most of its other functionality to the referenced ArrayCollection. You can probably start by subclassing ListCollectionView to do this.