You should be able to do what you want to do using XML files. However, if you're looking to have callers change the file, you could run into a race condition where 2 or more callers are changing the file at the same time and I don't know what problems that could cause if multiple copies of the file is being written at the same time. If your script is making decisions based on the contents of the XML file, you could have problems in your script's decision making process.
What kind of changes are callers making to the XML file?
Bill