  The interpretation of anaphors depends on their antecedents as the semantic
value that an anaphor eventually conveys is co-specified by the value of its
antecedent. Interestingly, when occurring in a given syntactic position,
different anaphors may have different sets of admissible antecedents. Such
differences are the basis for the categorization of anaphoric expressions
according to their anaphoric capacity, being important to determine what are
the sets of admissible antecedents and how to represent and process this
anaphoric capacity for each type of anaphor.
  From an empirical perspective, these constraints stem from what appears as
quite cogent generalisations and exhibit a universal character, given their
cross linguistic validity. From a conceptual point of view, in turn, the
relations among binding constraints involve non-trivial cross symmetry, which
lends them a modular nature and provides further strength to the plausibility
of their universal character. This kind of anaphoric binding constraints
appears thus as a most significant subset of natural language knowledge,
usually referred to as binding theory.
  This paper provides an integrated overview of these constraints holding on
the pairing of nominal anaphors with their admissible antecedents that are
based on grammatical relations and structure. Along with the increasing
interest on neuro-symbolic approaches to natural language, this paper seeks to
contribute to revive the interest on this most intriguing research topic.
