In its scans, an estimable XML schema for taxonomic publications must efficaciously detect and mark up (1) taxonomina (taxonomic names); (2) names or latitudinal and longitudinal coordinates of collection sites; (3) descriptive morphologic terms; and metadata such as terms denoting title, publisher, issue and abstract. The degree of nesting and the quantity of identificational (id) references in the schema must be moderate so that the performance of the resulting marked‑up document in responding to queries is not depressed. In its operation, the schema ought to preclude the production of redundant data in the marked-up document. The marked-up document ought not to be excessively large. The mark-up schema ought to be able to perform three types of fine-grained queries on all available online documents. These classes of queries are (1) nominal, (2) locational and (3) descriptive (conceptual). To ensure that descriptive terms are identified during scans, the relationship between any morphologic character and its description must be explicit.