In many languages with head-marked possession, some nouns require possessive marking and cannot be used alone. This distinction is also known as obligatory possessive inflection, and obligatorily possessed nouns often display a distinct morphological structure. For example, when they appear without an identifiable possessor, they may feature a special marker denoting their status as generic/unspecified possessed nouns. Alternatively, they may undergo additional nominalization and no longer require possessive marking. Obligatory possessed nouns are contrasted with optionally possessed nouns, which can display, but do not require, possessive marking. This distinction can also be used to identify alienable and inalienable possession.
NoPx: The language does not have possessive marking.
NoOblPxN: Possessive marking exists, but obligatory possessive marking on nouns does not exist.
OblPxN: Obligatory possessive marking on nouns exists.
 Consider the Navajo example in which the following semantic contrasts exist: (1) bi-be' ‘her [breast] milk’; (2) a-be' ‘somebody’s milk’ (unspecified possessor); (3) be-'a-be' ‘her [non-breast] milk’ (for example, store-bought).
 The commentary should explain whether any morphological strategies exist to transform obligatorily possessed nouns into non-obligatorily possessed nouns, and, if so, whether these resulting words can be optionally possessed. The existence of any semantic differences between an original, obligatorily possessed noun and its morphologically derived, optionally possessed counterpart should be detailed in the commentary.