Listanum

Listanum is a theoretical construct used in mathematical linguistics and information modeling to describe a finite, ordered collection of items that may include optional elements and attached annotations. The term is not part of standard mathematical or computer-science nomenclature and is used mainly in speculative or pedagogical contexts to illustrate the combination of sequence and feature annotation.

Etymology and scope. The word combines the English noun list with a Latin-like suffix, echoing taxonomic and mathematical coinages. It does not refer to a real natural object or widely adopted formal type, but serves as a convenient label for a structured sequence with meta-information.

Definition and notation. A listanum L is a sequence of positions i = 1, ..., n. Each position carries an element xi and a presence indicator pi that can be mandatory or optional. Elements xi may also bear attributes Ai, such as weight wi or a set of features Fi. A compact notation is L = [(x1, p1, A1), ..., (xn, pn, An)]. Optional positions can be present or omitted in a given realization of L, according to their presence indicators.

Operations and interpretation. Core operations include concatenation, projection (selecting a subset of positions), and filtering by attributes. These operations extend ordinary list operations while respecting presence indicators and attributes. In practical modeling, a listanum can represent a phrase structure with optional modifiers, a data record with optional fields, or a feature bundle with weighted components.

Applications and variants. Listanum concepts appear in theoretical discussions about how sequences interact with annotations, in pedagogy for illustrating optional constituents, and in lightweight modeling of structured data where both order and optionality matter. See also: list, sequence, optional, feature structure.