BibTeX is part of LaTeX. It's described even in Lamport's 1994 LaTeX book. Nelson has contributed a rigorous grammar for BibTeX and friends, and pioneered the storage and retrieval of BibTeX records in SQL databases. Crucial here is that BibTeX is flexible. Each record can include fields relevant only for search and retrieval, which won't appear in a citation.
Nelson finds the combination of BibTeX and SQL enormously valuable for documenting publications in books and journals, and on specific subjects, and by and about specific authors. He also contributes to large shared libraries of BibTeX records.
If you have another topic you'd like to discuss sometime this year, please do send me a message.