The range functions of FEEL (DMN 1.6, section 10.3.4.7, Table 79): before, after, meets, met by, overlaps, overlaps before, overlaps after, finishes, finished by, includes, during, starts, started by and coincides.

They are the relations of Allen's interval algebra, as the HL7 CQL has them, between points and ranges, and they give true or false. A point is a value that has an order (Table 55): a number, a string, a date, a time, a date and time, or a duration. A signature takes a point or a range in each place, and which one it is is told by the kind of the argument, so before(1, [5..10]) and before([1..10], 15) are two signatures of one function; the parameters of each have the names of the specification (point, range, point1, range2...), which a call by name tells apart.

What is written (D-79)

All fourteen, each signature by the formula of the table as it is printed. Not one is turned into another through a conversion of a point to a range: the point and the range forms of a function agree on every range that holds something, and they differ on an empty one, [p..p) (notes, 3.7). starts(1, [1..1)) is what the formula says.

Range-domain choices (D-79)

The table has no column for the domain, and the notes read (A1, A5, A6) as follows.

• An endpoint that is not there (< 10 has no start, >= 5 has no end, and [1..null] has none) is minus infinity as a start and plus infinity as an end, its side never included. Two starts that are not there are equal, so are two ends. before(5, < 3) is false, after(5, < 3) is true and includes(< 3, 2) is true; during(< 3, < 4) is true.
• A null, or an argument that is neither a point nor a range (a boolean, a list, a context, a function) is out of the domain: the call is null with an :argument_out_of_domain error. before(date, null) is null in FEEL; it is false in B-FEEL (section 11.2), and the dialects of this library are FEEL.
• Endpoints that cannot be compared with one another (a number and a string, a date and a date and time) are out of the domain as well. It is checked on all that are given, so a call is either null for that or has every comparison of its formula defined.
• A combination that is not a signature (meets(1, 2), finishes([1..2], 3)) is out of the domain.
• A range that holds nothing ((1..1), [5..1]) is a range as any other: the formulas are applied to its properties, which can give odd answers (both before and after can be true of one pair). Only a range value has the properties; (!= 10) has 10 on both sides, left out, and is read so.

A list of one point is that point (section 10.3.2.9.4).