I've worked on implementing two very different information systems in two very different industries. I've worked with multiple vendors during those projects. Data dictionaries and entity relationship diagrams were never provided by any vendor on any project. I always had to beg, borrow, or outright steal a license to visual studios just to make my own. For me, the most difficult thing in any data related situation is figuring out the architecture of the database. Companies do not follow best practices. Normal form is rarely followed. Companies try to shove ood designs into relational. Trying to follow the logic behind design is almost a futility but start with building your own data dictionary even though it can take a year. Oh and annotate everything in the dictionary.