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 Syntax
imports Base
begin
chapter {* Concrete syntax and type-checking *}
text FIXME
section {* Parsing and printing *}
text FIXME
section {* Checking and unchecking \label{sec:term-check} *}
end