Amount predicates

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Numeric amount predicates

In the current state of Lojban's lexicon, numeric amount predicates are few, most amount predicates are of the form "x1 has a large/small amount in this or that dimension, by standard x2" or such. Examples are {tsali}, {darno}, {clani}, {ganra}, {ditybra}, {sutra}, {tilju}… "x1 is strong / far away / long (length) / broad / long (duration) / quick / heavy…" Their objective/numeric counterparts would be something like "x1 is the stength / distance / length / breadth / duration / speed / weight ... of x2", thus relating an objective amount to something, without claiming this amount is large, small or medium.

There are several possible argument structure paradigms that could be suitable for implementing those numeric amount predicates; for consistency's sake, we should probably decide which of them will be the conventional paradigm, and model the argument structures of the future numeric amount predicates after it.

Possible paradigms

FIRST OPTION: There is one amount predicate for each measure scale
EXAMPLE: "The box is 2 kg" = {li re mass_in_kg_of lo tanxe}
BENEFITS: Compact.
DRAWBACKS: You are compelled to chose an unit of measure even when it's irrelevant.

SECOND OPTION: Each amount predicate has an argument slot for the unit of measure
EXAMPLE: "The box is 2 kg" = {li re mass_of lo tanxe la .kilogram.}
BENEFITS: The amount is expressed in a specific unit of measure, which can be specified explicitly by filling the unit argument slot, or left to the context when appropriate.
DRAWBACKS: Leaving the unit slot up to the context might lead to ambiguities, and always having to fill it explicitly may be bothering.

THIRD OPTION: Amount predicates are unitless and return an opaque quantity (you could imagine it being expressed with an unknown but constant unit, maybe Plank units or whatever); if need be, in order to measure an amount on a specific scale, the opaque amount has to be converted to the desired unit with another predicate, or multiplicated by an appropriate conversion value.
EXAMPLE:
"The box is 2 kg" = {li re pi'i mo'e la .kilogram. cu mass_of lo tanxe}
or {lo pilji be li re bei la .kilogram. cu mass_of lo tanxe}
or {li re mass_to_kg lo mass_of be lo tanxe}
or {li re pi'i ky gy cu mass_of lo tanxe}, with "ky gy" being a kilogram to opaque mass conversion value.
BENEFITS: You can talk about size, length, weight etc without being compelled to mention any unit, as when comparing the size of two objects, etc.
DRAWBACKS: A multiplication or unit conversion is needed for extracting a number on a specific scale of measure, resulting in more verbosity.

FOURTH OPTION: Amounts are epxressed by using {va'e}.
EXAMPLE: "The box is 2 kg" = {lo tanxe cu re va'e lo ka ki'ogra}, or {lo tanxe cu re va'e ky gy}.
BENEFITS: Pretty concise.
DRAWBACKS: You need to resort to {mo'e} to put a pronoun into the number slot of {va'e}.

FIFTH OPTION: The Toaq Dzu Way.

Notes

In the official gismu list, {junta} seems to be the only genuine numeric amount predicate, and as it has no mention of any specific unit in its definition, it seems to match the third paradigm described above.