[RIF-APS] Rules Sign

Hello,

 

With respect to the abridged presentation syntax there is still an open
issue about the sign to distinguish the head and the body of a rule.

 

Currently, we use ":-" in the examples e.g. in UCR and PRD, which is
well-known in the logic community but not so much in others including
production rules.

 

I shortly discussed this issue with the BLD/FLD editors Michael and Harold
and we came up with this unambiguous proposal to distinguish classical
implication and rules head and body.

 

<== for PRD and BLD

<-- for classical

 

<== and <-- might be also reverted ==> -->

 

-Adrian