What would be a good replacement for $InputFileName
(which has been added recently to Mathematica 8) to achieve backwards compatibility with let's say M6 and M7?
I am using it for loading auxiliary data from a package file and found that it is a convenient way to use relative paths for this purpose. However, I am not sure how to achieve this in M6 and M7.
For example,
$PackageDir=DirectoryName[$InputFileName];
svgParser=XML`Parser`InitializeXMLParser["svg",
FileNameJoin[{$PackageDir,"Cache/svg10.dtd"}]]