rivt is an open source software project for writing engineering documents. Documents are formatted as text, HTML or PDF files (rivt docs) that are generated from rivt markup text files (rivt files).
A rivt file is a Python file (.py) that imports the rivtlib Python package and interprets rivt markup. A rivt file can publish docs in all formats and can be compiled with other docs into a rivt report. This site is an example of a rivt report.
Small rivt file examples are provided here and here. An interface for searching rivt files on GitHub is here.