Example with weather, dates and trust

clear(auto).
set(prolog_style_variables).
set(hyper_res).
set(factor).
clear(print_given). 
set(print_kept). 
assign(stats_level, 0).
assign(max_seconds, 10).

list(sos).

% temperature in Tallinn is -5 at day one with trust 1:
% here "id1" is an id of the encoded fact

rdf("id1","subject","Tallinn").
rdf("id1","property","temperature").
rdf("id1","object","-1").
rdf("id1","date",1). % 1 is today
rdf("id1","trust","1"). % 1 is full trust

% combine the reified triplets to a fact encoding
% also date and trust where
% rdfdt(subject,property,object,date,trust)

-rdf(X,"subject",Y) | -rdf(X,"property",Z) 
| -rdf(X,"object",V) | -rdf(X,"date",W) | 
  -rdf(X,"trust",O) | 
  rdfdt(Y,Z,V,W,O).

% temperature the next day is the same as today,
% but with twice smaller trust: also, do not derive
% anything with trust less than 0.2

-rdfdt(X,"temperature",Y,U,T) | -$FLT("0.2",T) | rdfdt(X,"temperature",Y,$SUM(U,1),$FPROD(T,"0.5")).

% rdfd is rdf with date but no trust:
% rdfdq(subject,property,object,date)

rdfd("Tallinn","temperature","-5",2). % tomorrow

rdfd("Tallinn","weatherfeature","stormy",2). % tomorrow

% if stormy, then also windy:

-rdfd(X,"weatherfeature","stormy",U) | rdfd(X,"weatherfeature","windy",U).

% various degrees of badness:

% rdfdq is a rdf with date and qualifier:
% rdfdq(subject,property,object,qualifier,date)

-rdfd(X,"temperature",Y,U) | -$FLT(Y,"-0") | rdfdq(X,"weatherfeature","badness",1,U).

-rdfd(X,"temperature",Y,U) | -$FLT(Y,"-20") | rdfdq(X,"weatherfeature","badness",2,U).

-rdfd(X,"temperature",Y,U) | -$FLT(Y,"0") | -rdfd(X,"weatherfeature","windy",U) | rdfdq(X,"weatherfeature","badness",3,U).

end_of_list.