For different desktops and applications to have access to the same information, a protocol for storing the recent file list has to be determined. An XML document will be used, of the form below:

<?xml version="1.0"?>
<RecentFiles>
  <RecentItem>
    <URI>file:///home/jwillcox/testfile.txt</URI>
    <Mime-Type>text/plain</Mime-Type>
    <Timestamp>1028181153</Timestamp>
    <Private/>
    <Groups>
      <Group>Recent File Test</Group>
    </Groups>
  </RecentItem>
  <RecentItem>
    <URI>file:///home/jwillcox/recent-file-spec.xml</URI>
    <Mime-Type>text/xml</Mime-Type>
    <Timestamp>1028181158</Timestamp>
    <Private/>
    <Groups>
      <Group>Recent File Test</Group>
    </Groups>
  </RecentItem>
</RecentFiles>
    

The URI, Mime-Type, Timestamp tags are required, but the Private, Groups, and Group tags are not. The Timestamp tag should be the number of seconds sinced the Epoch when the item was added to the list. The Group tags exist for the purpose of making groups of items with an arbitrary set of MIME types. A single item can belong to an unlimited number of groups. If the Private tag is specified, it means that implementations should only include the item if requestor has specifically asked for items in a group that the item belongs to. For instance, maybe a file selector would like to hold a list of directories that you have recently saved files in, and allow you to choose from one of these next time you save a file. You wouldn't want those directories showing up in the "Recent Documents" menu. If the items are put into the "File Selector Save Directories" group and marked as private, this problem is solved.

All text in the file should be stored in the UTF-8 encoding. No local paths are allowed in the URI tag. They should be converted to a valid URI with a "file" scheme. Items with the same URI should not be allowed. If a duplicate is found, it should have its timestamp updated, and any new groups added to it. No other information should be changed. The document should be stored in "~/.recently-used", and it should contain no more than 500 items.

Before reading or writing the document, it should be locked using the POSIX lockf() mechanism, and unlocked when finished.