I'm sure there's something about this in BOL somewhere, but this cost me a few more than a few ticks yesterday. Hoping to save you a few ticks. This one deals with semantic models used by Report Builder (part of SSRS 2005).
Suppose you have a semantic model deployed on server A that you want to move to server B. You don't have the source code. Perhaps it "arrived" pre-deployed on a VPC, as an example. You need the .smdl file. But it doesn't exist standalone, its been deployed to the Report Server. Or at least I didn't find it. I could probably write a program to extract it using the admin web service interface. But I'm too lazy.
So, eventually, I brought up the web interface, selected the model, then, under "Model Definition" chose "Edit". A nice dialog box asked me where I wanted to put the .smdl file. Great, just what I wanted.
BTW, bringing up SSMS, and browsing to the model in Object Browser, the model had a nice dropdown menu item, "Script As…". Problem was, it didn't seem to script anything. I tried all three script options, nothing happened.