simplified/refined document model: collection of named nodes, without proper dependencies yet;
moved basic type definitions for ids and edits from Isar_Document to Document;
removed begin_document/end_document for now -- nodes emerge via edits;
edits refer to named nodes explicitly;
theory Isar
imports Base
begin
chapter {* Isar language elements *}
text {*
The primary Isar language consists of three main categories of
language elements:
\begin{enumerate}
\item Proof commands
\item Proof methods
\item Attributes
\end{enumerate}
*}
section {* Proof commands *}
text FIXME
section {* Proof methods *}
text FIXME
section {* Attributes *}
text FIXME
end