The UK BIM Protocol does not explicitly indicate a sheet naming convention. It is good practice to use the number field of a filename as the placeholder for sheet numbers. That way a printed document can always be identified correctly even if it were found lying about some the table in the office or even on site (a printed sheet is a document of its own). I use the United States National CAD Standard (NCS) sheet naming convention. Now imagine we must generate sheets for a 100-level skyscraper from a federated model. What characters would we use?

Number of characters per field:

• Role = 2
• View Type = 1
• Number = 2

If only numbers were used, then only a total of 99 sheets could be generated for all 100 levels. Clearly, we need more characters (the Chinese have a natural advantage over us here). We could be silly and propose Wingdings, but a more sensible choice for the English-speaking world would be to use the United Nations Military Alphabet. Its what most of us use when we need to phonetically convey information to someone else over a faint telephone line anyway. Suppose we use numbers and capital letters to denote the sheets then we never need to worry about specifying small caps, although it is a very real possibility if we still do not have enough characters to go around. The font to use for this alphabet is discussed here: Revit 2020 Consolas Font for BIM because of Slashed Zero

There are 10 characters in the numbers and 26 in the alphabet, giving us a total 36 possible representations per character. The result below should be serving as an indication that the naming system will serve its purpose.

I purposefully left a gap between levels in Numbering so that sheets may be inserted as required between A and L.