\frenchspacing for formal isabelle style avoids extra space in situations like ``@{text "?"}'' followed by plain text;

--- a/lib/texinputs/isabelle.sty	Thu Jun 09 10:59:25 2011 +0200
+++ b/lib/texinputs/isabelle.sty	Thu Jun 09 11:26:25 2011 +0200
@@ -18,14 +18,14 @@
 %symbol markup -- \emph achieves decent spacing via italic corrections
 \newcommand{\isamath}[1]{\emph{$#1$}}
 \newcommand{\isatext}[1]{\emph{#1}}
-\DeclareRobustCommand{\isascriptstyle}{\def\isamath##1{##1}\def\isatext##1{\mbox{\isastylescript##1}}}
+\DeclareRobustCommand{\isascriptstyle}{\def\isamath##1{##1}\def\isatext##1{\mbox{\frenchspacing\isastylescript##1}}}
 \newcommand{\isactrlsub}[1]{\emph{\isascriptstyle${}\sb{#1}$}}
 \newcommand{\isactrlsup}[1]{\emph{\isascriptstyle${}\sp{#1}$}}
 \newcommand{\isactrlisub}[1]{\emph{\isascriptstyle${}\sb{#1}$}}
 \newcommand{\isactrlisup}[1]{\emph{\isascriptstyle${}\sp{#1}$}}
-\DeclareRobustCommand{\isactrlbsub}{\emph\bgroup\math{}\sb\bgroup\mbox\bgroup\isastylescript}
+\DeclareRobustCommand{\isactrlbsub}{\emph\bgroup\math{}\sb\bgroup\mbox\bgroup\frenchspacing\isastylescript}
 \DeclareRobustCommand{\isactrlesub}{\egroup\egroup\endmath\egroup}
-\DeclareRobustCommand{\isactrlbsup}{\emph\bgroup\math{}\sp\bgroup\mbox\bgroup\isastylescript}
+\DeclareRobustCommand{\isactrlbsup}{\emph\bgroup\math{}\sp\bgroup\mbox\bgroup\frenchspacing\isastylescript}
 \DeclareRobustCommand{\isactrlesup}{\egroup\egroup\endmath\egroup}
 \newcommand{\isactrlbold}[1]{{\bfseries\upshape\boldmath#1}}
 \newcommand{\isactrlloc}[1]{{\bfseries\upshape\boldmath#1}}
@@ -40,13 +40,13 @@
 \isamarkuptrue\par%
 \isa@parindent\parindent\parindent0pt%
 \isa@parskip\parskip\parskip0pt%
-\isastyle}{\par}
+\frenchspacing\isastyle}{\par}
 
 \newenvironment{isabelle}
 {\begin{trivlist}\begin{isabellebody}\item\relax}
 {\end{isabellebody}\end{trivlist}}
 
-\newcommand{\isa}[1]{\emph{\isastyleminor #1}}
+\newcommand{\isa}[1]{\emph{\frenchspacing\isastyleminor #1}}
 
 \newcommand{\isaindent}[1]{\hphantom{#1}}
 \newcommand{\isanewline}{\mbox{}\par\mbox{}}