Filters

Filters are a special kind of rule that remove unwanted results. Filters are very useful because they can deal with exceptions, which are very common in languages: you can make a general rule, and then filter the exceptions.

Filters look like annotations, where the attribute concept points to the annotation that needs to be filtered out:

Syntax:

wow::filter@(concept=”annotation”)

Example:

lexicon : { apple, kiwi, melon } = Fruit;

rule :
{
    "Adam" "\'s"
    { "apple" } = wow::filter@(concept="Fruit")
};

“He has an apple and a big Adam’s apple”

{Sentence
    t(0,2) "He" (init-cap, init-token)['he':Pron-Pers]
    t(3,6) "has" ['have':V-Pres-3-Sg-have]
    t(7,9) "an" ['a':Det-Indef]
{Fruit
    t(10,15) "apple" ['apple':Nn-Sg]
}Fruit
    t(16,19) "and" ['and':Conj-Coord]
    t(20,21) "a" ['a':Det-Indef]
    t(22,25) "big" ['big':Adj-Std]
    t(26,30) "Adam" (init-cap)['Adam':Prop-Std, +giv]
    t(30,32) "'s" [''s':Part-Poss]
    t(33,38) "apple" ['apple':Nn-Sg]
}Sentence

You can also use regular expressions in your filters (ECMAScript regex notation):

lexicon:
{
    chicken
} = Poultry_Animal;

lexicon:
{
    salmon
} = Fish_Animal;


// chicken pie is no animal
rule:
{
    <>
    'pie'
} = wow::filter@(concept=/.*Animal/);

Try:

wow -p english,rules -i “I like chicken, I like salmon, I like chicken pie and salmon pie.”

Output:

t(0,1) “I” (init-token)[‘I’:Pron-Pers]

t(2,6) “like” [‘like’:V-Pres, +inf, +positive]

{ Poultry_Animal

t(7,14) “chicken” [‘chicken’:Nn-Sg]

} Poultry_Animal

t(14,15) “,” [‘,’:Punct-Comma]

t(16,17) “I” [‘I’:Pron-Pers]

t(18,22) “like” [‘like’:V-Pres, +inf, +positive]

{ Fish_Animal

t(23,29) “salmon” [‘salmon’:Nn-Sg]

} Fish_Animal

t(29,30) “,” [‘,’:Punct-Comma]

t(31,32) “I” [‘I’:Pron-Pers]

t(33,37) “like” [‘like’:V-Pres, +inf, +positive]

t(38,45) “chicken” [‘chicken’:Nn-Sg]

t(46,49) “pie” [‘pie’:Nn-Sg]

t(50,53) “and” [‘and’:Conj-Coord]

t(54,60) “salmon” [‘salmon’:Nn-Sg]

t(61,64) “pie” [‘pie’:Nn-Sg]

t(64,65) “.” [‘.’:Punct-Sent]

As you can see “chicken” and “salmon” when followed by pie are no longer found as animals.

Note as well that the filter can function on a bigger scope than the annotation itself, it takes all annotations of type “concept” from the capture and filters them out.

You can also delete attributes, without deleting the concepts:

wow::filter@(concept=”name_of_concept”,name_of_attribute=”value”)

This can be very useful to fine-tune results. For instance, in the sentence:

Alexandria , Virginia

We get that Alexandria is a City in Egypt, but the context shows that in this case, it refers to a city in the USA.

To fix it, we can use the following rule:

rule:
{
    {
        City
    } = wow::filter@(concept="City",country=/(?!USA).+/)
    <'\,'>
    USState
};

Because of the context (we have a USState), we want to get rid of all countries that are not USA, to do that we use the regular expression: /(?!USA).+/

• City -> Alexandria @ country=USA;