AppleScript: The Definitive Guide, 2nd Edition

Missing External Referents

AppleScript is a little language, leaving it up to externals such as scriptable applications and scripting additions to extend the vocabulary of the language as needed. A consequence of this architecture is that at various crucial moments during the life of a script, such as when it is compiled, decompiled, or executed, AppleScript will look for externals, and may complain if it can't find them. This section talks what happens on these occasions.

Application Missing at Compile Time

When a script is compiled, AppleScript needs each application targeted by that script, so that it can obtain its dictionary to verify the legality of the terms the script is using and to translate those terms into Apple events in bytecode. If it can't find a targeted application, it will present a dialog asking you, the human user, to locate it. At this point, one of three things can happen:

You cancel out of the dialog.

The script won't compile.

You locate the correct application.

The script compiles, and is modified to point to the application you nominated.

You locate some other application.

The script won't compile.

What consitutes "the correct application" is any application whose dictionary defines the terminology AppleScript is trying to verify. To see what I mean, let's start with code like this:

get disk 1

If that's all your script says, it won't compile at all, because the term disk isn't part of the AppleScript language. You can use it this way only while targeting a scriptable ...