16. A computer program product tangibly embodied in a machine-readable storage device, the computer program product including instructions that, when executed, cause a processor to perform operations when a new tag name is to be added to a collection of tag names, the operations comprising: receiving, in a computer system, a new tag name that is to be added to a collection of existing tag names that conform to a standardized protocol for defining semantics of contents in electronic communications, the new tag name including at least first and second terms; determining whether the collection already includes any of the first and second terms, wherein each term included in the existing tag names is associated with one of several unique identifiers; selecting at least first and second unique identifiers for the new tag name, wherein, for any of the first and second terms that is already included in the collection, a corresponding one of the several unique identifiers associated therewith is selected; wherein the first unique identifier is associated with the first term and the second unique identifier is associated with the second term, and wherein the new tag name signifies that the second term is a qualifier for the first term in accordance with the standardized protocol; and wherein the collection further includes a third term that is currently not qualified by the second term, further comprising updating the collection so that the second term qualifies also the third term, the second unique identifier being associated with the second term both for qualifying the first term and the third term.
16. A computer program product tangibly embodied in a machine-readable storage device, the computer program product including instructions that, when executed, cause a processor to perform operations when a new tag name is to be added to a collection of tag names, the operations comprising: receiving, in a computer system, a new tag name that is to be added to a collection of existing tag names that conform to a standardized protocol for defining semantics of contents in electronic communications, the new tag name including at least first and second terms; determining whether the collection already includes any of the first and second terms, wherein each term included in the existing tag names is associated with one of several unique identifiers; selecting at least first and second unique identifiers for the new tag name, wherein, for any of the first and second terms that is already included in the collection, a corresponding one of the several unique identifiers associated therewith is selected; wherein the first unique identifier is associated with the first term and the second unique identifier is associated with the second term, and wherein the new tag name signifies that the second term is a qualifier for the first term in accordance with the standardized protocol; and wherein the collection further includes a third term that is currently not qualified by the second term, further comprising updating the collection so that the second term qualifies also the third term, the second unique identifier being associated with the second term both for qualifying the first term and the third term. 17. The computer program product of claim 16 , wherein the collection further includes fourth and fifth terms that are subqualifier terms for the second term, the fourth and fifth terms having associated therewith fourth and fifth unique identifiers, respectively, wherein the fourth and fifth unique identifiers are associated with the fourth and fifth terms both when the second term qualifies the first term and when the second term qualifies the third term.