+
+The approaches experimented-with so far, numbered in chronological order of
+origin (i.e. later versions do not _necessarily_ obsolete earlier ones, they're
+just different):
+
+### v1
+A single, synchronous script, saving state in text files (Bash and AWK).
+
+### v2
+Parallel processes: collectors, cacher and reporters; passing messages over pipes
+(Bash and AWK).
+
+### v3
+Clean-up, polish and further development of main ideas learned in v2.