distal dog ugly-ADJ.PRED 'yon dog is ugly'
would be distinct from:
distal dog ugly-ADJ.ATTR 'yon ugly dog'
I wonder if this is attested in the world's languages, and if not, if it could be part of a possible human language.
In German, attributive adjectives agree in number and gender, while predicative adjectives (which are used with a copulative verb) do not, and are invariable. In fact, some analyses of German consider the predicative adjectives and deadjectival adverbs to in fact belong to the same category of speech, since an adjective used as an adverb also does not agree and takes the same "default" form.
In Arabic, adjectives agree in number, gender, and case with their referents, but attributive adjectives are distinguished from predicative adjectives by also needing to agree in definiteness. In predicative sentences with adjectives, there is no overt copula for the present tense, so a sequence of definite noun + attributive adjective is distinguishable from an equational sentence consisting of a definite noun + indefinite predicative adjective. (Predicative adjectives can also be marked for definiteness when the semantics of the sentence calls for it.)
Russian has this feature, too: этот больной человек 'this sick person' vs. этот человек болен 'this person is sick'.
For example German: Der hässliche Hund ~ Der Hund ist hässlich.
In Finnish, attributive and predicative adjectives have different agreement patterns when they are modifying mass-nouns and (most) plural count-nouns.
valkoinen lumi "the white snow" (mass-noun)
pitkät ihmiset "the tall people" (plural count-noun)
Here, valkoinen "white" and pitkä "long, tall" are in the nominative, just like their head nouns. But, when these adjectives are used predicatively with the same nouns, they appear in the partitive case:
Lumi oli valkoista "The snow was white"
Ihmiset olivat pitkiä "The people were tall"
This pattern doesn't apply to singular count-nouns:
valkoinen lintu "white bird"
Lintu oli valkoinen "The bird was white"
Also North Saami: Gákti lea čáppat "The jacket is nice" (čáppat), Dát lea čappa gákti "This is a nice jacket".