CHM: Calling up F1 Topic: Map ID vs. Keyword

[Keith Hansen]

In one of our applications, we use a CHM as the Help file. In the
application, when the user clicks in the Address text box (for example)
and presses F1, a Help topic describing that text box appears.

In the past, I've always seen Map IDs used to call up such F1 topics.
However, there is apparently another way to do this: 

* A topic file name from the RoboHelp project (such as Address.htm) is
used in the application code as a "keyword" to call up the F1 Help
topic. 

* Apparently, the HTM file is somewhere embedded within the CHM(?!), and
the Address.htm topic can be located and then opened.

Now, I've seem direct calls to an HTM Help topic filename in
WebHelp--but this is a CHM! There is only a single, compiled Help file
connected to the application. It's not a bunch of separate HTM files,
like a WebHelp project.

Can anyone comment on this method of calling the F1 Help? What are the
pros and cons of keyword vs. Map ID?

One con is obvious to me. If you use Map IDs, you can change file names
in your RoboHelp project whenever you wish. If the Map ID remains
unchanged, there is no problem.

With this "filename as keyword" method, if the topic filename is
changed, a corresponding change must be made in the application code. To
me, this is a major drawback.

Comments, please! 

Keith