This document conforms to the TAS3 project-wide glossary [TAS3GLOS] reproduced in Annex I.
If you are a nontechnical reader you may want to start from Annex D to get overall understanding of the user experience, then skim the main document and perhaps consulting Figs 1 and 2 may be useful. You should also consult [TAS3BIZ], reproduced in Annex E "Business Model", which gives a good motivation for the work shown here. You may also find [TAS3WP] and web site www.tas3.eu helpful in understanding the overall TAS3 concept.
If you are a researcher, this document is the right place to start to see where your research may fit within the architecture.
If you are a software developer you will want to read this document, but you will also want to read carefully Annex A "Protocols", which details protocol versions and gives suggestions about available open source packages that implement these protocols.
If you are a deployer, you should skim this document, perhaps look at Annex A "Protocols", and then work through Annex C "Compliance" as you prepare for your TAS3 certification.
If you are a reviewer, you should read Section 2 and then any other sections or annexes that interest you.