This is a style of modeling the mixes text and diagrams in one document with cross-references.
Inspired by DonaldKnuth's LiterateProgramming.
Introduce(?) by Jim Arlow and Ila Neustadt, In their "Enterprise Patterns and MDA..." published by Addison-Wesley in 2003.
Described and motivated on page 98. There book illustrates the style and I find it quite understandable as a result.
See also PartitionOfModelsIntoPicturesAndText, IllustrationsClarifyText, TotalModeling