What is the most important basis for bidding units to prepare tender documents?

The main basis for the preparation of tender documents are: 1, national and industry standards; 2, the user's bidding documents stipulate the content; 3, the user's on-site working condition requirements; 4, the unit's product design and production information. Among them, the most direct, but also the most important basis is of course the user's bidding documents of the relevant requirements, which also includes a variety of technical standards based on the tender!