A Fudge message may have an optional Taxonomy. This is a numerical value that specifies a set of ordinal<-->name mappings that apply to the messages that share that Taxonomy.
The rationale for the inclusion of taxonomies into Fudge is that:
- Working with string-based field names is a desirable feature, because it makes coding and introspecting far easier than just working with index- or ordinal-based message encoding.
- Including string-based field names in a message is an unnecessary performance hit in a high-performance system.
Thus, taxonomies allow you to do all your coding using field names, but not transmit those when the message is encoded to a series of bytes. Rather, just a taxonomy ID is transmitted, along with the ordinals matching those field names. At decoding time, the taxonomy is looked up, and field names are restored.
Taxonomies are not strictly appropriate for long-term persistence of Fudge messages, because the taxonomy might change over time, or be lost. Therefore, when writing to disk or another persistent message format, field names should be restored. The taxonomy could be stored using an approach such as the Fudge Encoded Taxonomy, however conventional compression techniques on a storage medium may give a similar space saving.