Chain [ … ]

A chain is an easy way to implement if-else statements. When you surround rules with a chain, the first one will be run, if it matches, than the rest of the rules are ignored. If it doesn’t, the second rule will be tried, and so on.

lexicon:
{
nice,
polite
}  = adj_pos;



chain
[
    rule :
    {
          'be' 'not' .. adj_pos
    } = Negative;

    rule :
    {
          'be' .. adj_pos
    } = Positive;
]

“That man is not always polite. His wife is nice.”

Sentence -> That man is not always polite .
Negative -> is not always polite
adj_pos -> polite
Sentence -> His wife is nice .
Positive -> is nice
adj_pos -> nice

If we would not put the rules in a chain the first sentence would also match the second rule (<’be’> .. adj_pos) and we would end with a Positive as well as a Negative result that we would need to filter.