This RFC describes how grammar engineers should format their grammar version string in Version.lsp so it is useful with other software.

Following convention, the string should contain the name of the grammar with the date of the release in parentheses. For example, here is Jacy's string:

(defparameter *grammar-version* "Jacy (090705)")

See below for details on how to format the date.

The preferred approach is to use the output of the Unix date command with the --rfc-3339=date option:

$ date --rfc-3339=date
2011-07-24

This results in a string formatted as YYYY-MM-DD

As long as the string is compatible with the Unix date command, it is acceptable. For instance:

$ date --rfc-3339=date --date="today"
2011-07-24
$ date --rfc-3339=date --date="110723"
2011-07-23

Simply having the year and month is not compatible, as it is interpreted as being the time of the current day (shown below with the standard output of the date command):

$ date --date="today"
Sun Jul 24 17:32:24 PDT 2011
$ date --date="1010"
Sun Jul 24 10:10:00 PDT 2011
$ date --date="10-10"
date: invalid date `10-10'

Developers could use "today" for the string on trunk, meaning that it is currently the most up-to-date version. This interpretation would break if a repository checkout has gone stale (not updated to the most recent change), but it might be preferable to having to manually update the version string for every commit.

(add your comments here, and/or edit the proposal above)