The Technology Assessment Directorate was an organization within Starfleet which made decisions regarding the technological requirements of certain Starfleet projects, including starbase construction, then requested bids of independent civilian contractors and issued contracts. They generated a lengthy and complex report regarding the plans to build Starbase Deep Space 10 sometime prior to 2376. (CoE eBook: Troubleshooting) The TAD classify Deep Space 9 as a "Hybrid Planar-Columnar Triradial structure". (DS9 reference: Star Trek: Deep Space Nine Technical Manual)