MIME and .desktop files in KDE

[nupul]

Well I am slighlty (understatement ) confused between the use of mime types and .desktop files ...let me tell you w.r.t. KDE what i know.

1. As per the standard, .desktop files are used to know which program is to be used to launch a particular file.

2. We detect the MIME type of a file and then try to figure out which program to use to open a particular type of file - (Does KDE do this? How....is there a central database to refer? Like in GNOME there is an association-registry, a complete list of programs to use to open a particular type of file. A new application can "register" itself along with its associated files in this DB. How can one achieve the same in KDE?)

Well, now the thing is this....if both of the above serve a similar purpose what is it that KDE does?

-How does KDE know which program to associate with a particular type of file (MIME)? Then why the need of .desktop files?

-we can check the file associations and the corresponding applications to use, in Yast>KDE Components>File Associations. Can I add my application's settings to this as well as retrieve the associations from my application? (from some file that is)

also could you please tell me when and why should one use the following commands:

desktop-file-install
update-desktop-database
update-mime-database

-does KDE use these commands for the above mentioned scenario?

...well there are more doubts but will clarify them based on your answers

Thanks

Nupul.

PS: please don't hastily reply saying look at the KDE sources...I have already done that, but sources help you understand the implementation, not the concept. I wish to understand the working and not it's underlying implementation.