Q: Making an XEmacs package

Hi. I am planning to make an XEmacs package one day (out of eSMS) and needs some information of how to do that. There will probably come a series of questions regarding this. I partially document my experiences so I may come up with some documentation patches for the lispref.texi file during all this. Please don't give me a RTFM, since it may actually be TFM I'm criticising. In the lispref there's a section describing Defining Global Variables. A lot of stuff regarding defvar is mentioned and one should start the documentation string with an asteriks to indicate it's a user option, the text also refers to the function `edit-options' which is not declared in XEmacs. So to me it looks like much of this information (even big parts of lispref) is left-overs from GNU Emacs. As I see it user-options should not be declared with `defvar', but rather `defcustom'. does that make `defvar' obsolete? Since a variable is either a "constant" that is not intended for user modifications (using `defcons') or it's a user customisation (using `defcustom'), can anyone come up with an example of when it's appropriate to use `defvar'? Can anyone point me to some documentation on how to make the jump from a simple *.el-file to a real integrated XEmacs package? A list of criterias on file/directory-structure, etc. would be nice. Jarl