Birchbark rules

[iad58]

Seventeen years ago, in my early weeks as a postgraduate student in Edinburgh, I noticed a strange punctuation mark, or should I say a combination of such, that people there were using. It consisted of a colon followed by a dash, and was used where something was defined (or illustrated, or enumerated), instead of a mere colon or a plain dash.

For a while I wondered what this local tradition meant. Then I understood. Edinburgh Prolog! The syntax introduced by Clocksin and Mellish! The colon-dash operator in Prolog rules written in the Edinburgh syntax! Suddenly it all made sense.

But now we see the colon-dash sequence in birchbark letters from Old Russa (here or here). Was Prolog (Edinburgh Prolog) invented in Russia then?

(А некоторые думают, что это улыбочка. Зря думают. Было бы так, будь Россия ее родиной, ее бы не называли по-русски аглицким словом.)