  Isabelle/jEdit is the main application of the Prover IDE (PIDE) framework and
the default user-interface of Isabelle, but it is not limited to theorem
proving. This paper explores possibilities to use it as a general IDE for
formal languages that are defined in user-space, and embedded into informal
text documents. It covers overall document structure with auxiliary files and
document antiquotations, formal text delimiters and markers for interpretation
(via control symbols). The ultimate question behind this: How far can we
stretch a plain text editor like jEdit in order to support semantic text
processing, with support by the underlying PIDE framework?
