Tradacoms is an early standard for EDI (Electronic Data Interchange) primarily used in the UK retail sector.
The UK Book Trade also has additional transactions defined for Orders, Issues, and Price & Availability Updates.
This avoids the duplication of common header and trailer information which can occur in a series of EDIFACT messages.
The best reference sources are the EDI websites of major retail hubs and industry associations.
Development is still happening under the auspices of BIC who initiate and moderate discussions and maintain the standard on behalf of the book industry.