Frank Mittelbach wrote:
> thanks for enlarging the test samples this is really helping a lot

Well, here is another sample. I tried to implement per chatper TOCs.
The main problems I encountered were

 o The old version of `processcontents' deletes the TOC file after
   reading it. (So the second TOC is empty.)

 o In order to have a clean interface between `processcontents' and
   `contentsobject' I moved the test (depth > tocdepth) out of
   the latter. Instead, `processcontents' defines a function
   \IfPrintTOCEntry which takes the serial number, depth, and some
   code, and decides whether the entry should be printed or not.

PS: The implementation below is rather quick and ugly.

Achim
________________________________________________________________________
                                _                             | \_____/ |
    //  Achim Blumensath       | \  _                        \O/ \___/\ |
   //   [log in to unmask]   |-< /_\                       =o=  \ /\ \|
 \X/    (p^2 - m^2)\psi = 0    |_/ \_                        /"\   o----|
____________________________________________________________________\___|

=== test.tex ===

\documentclass{article}
\RequirePackage{xparse}
\RequirePackage{template}
\IgnoreWhiteSpace
\DeclareTemplateType{contentsobject}{6}
\DeclareTemplateType{processcontents}{1}
\def\comma{,}

\newdimen\COpnum@width

\DeclareTemplate{contentsobject}{AB}{6}{
  pre-v-action     =f0 [\endgraf] \COpre@action,
  object-decls     =f0 [\relax]   \COobject@decl,
  object-indent    =l  [0pt]      \leftskip,
  number-width     =l  [0pt]      \@tempdima,
  right-margin-sep =l  [25pt]     \rightskip,
  pnum-width       =l  [15pt]     \COpnum@width,
  number-indent    =l  [0pt]      \parindent,
  number-format    =f1 [#1\hfil]  \COnumber@format,
  title-format     =f2 [#1]       \COtitle@format,
  pnum-format      =f1 [\hfil#1]  \COpnum@format,
  leaders-action   =f0 [.]        \COleaders@action,
  leaders-sep      =l  [4pt]      \@tempdimc
}
{
  \IfPrintTOCEntry{#1}{#2}
  {
    \DoParameterAssignments
    \COpre@action
    \COobject@decl
    \parfillskip=-\rightskip
    \parindent=0pt
    \@afterindenttrue
    \interlinepenalty\@M
    \leavevmode
    \IfNoValueT{#3}{\def\COnumber@format##1{\hfil}}
    \hbox to \@tempdima {\COnumber@format{#3}}
    \nobreak
    \COtitle@format{#4}{#5}
    \nobreak
    \leaders\hbox{
      \kern\@tempdimc
      \hbox{\COleaders@action}
      \kern\@tempdimc
    }\hfill
    \nobreak
    \hbox to \COpnum@width {\COpnum@format{#6}}
    \endgraf
  }
}

\newif\if@TOC@ChapterFound

\newcounter{tocstart}
\newcounter{tocmindepth}

\def\IfPTE@main#1#2#3{\ifnum #2>\c@tocdepth\else#3\fi}
\def\IfPTE@chapter#1#2#3{
  \ifnum #1<\c@tocstart                  % skip entries, until the chapter is
found
  \else
    \ifnum #1=\c@tocstart
      \c@tocmindepth=#2                  % chapter is found, next entries will
be printed
    \else
      \ifnum #2>\c@tocdepth
      \else
        \ifnum #2>\c@tocmindepth         % if end of chapter isn't reached,
print entry
          #3
        \else
          \c@tocmindepth=\c@tocdepth     % if end is reached, don't print any
entries
          \advance\c@tocmindepth by 1
        \fi
      \fi
    \fi
  \fi
}

\DeclareTemplate{processcontents}{AB}{1}{
  start-action   =f0 [\relax]   \COstart@action,
  end-action     =f0 [\relax]   \COend@action,
  file-name      =n  [\jobname] \COfile@name,
  file-extension =n             \COextension,
  contents-depth =c  [2]        \c@tocdepth,
  contents-start =c  [0]        \c@tocstart,
  collection-id  =n  []         \COcollection@id,
  heading        =f0 [\section*]\COheading,   %actully use some instance
  name           =n  [\contentsname] \COname,
  header-format  =f0 [\MakeUpperCase] \COheader@format
}
{
 \DoParameterAssignments
 \COheading{\COname
      \@mkboth{\CO@header@format\COname}{\CO@header@format\COname}}
 \begingroup
 \UseCollection{contentsobject}{\COcollection@id}
 \makeatletter
 \IfNoValueTF{#1}
   {\global\let\IfPrintTOCEntry\IfPTE@main}
   {\global\let\IfPrintTOCEntry\IfPTE@chapter
    \global\c@tocstart=#1}
 \@TOC@ChapterFoundfalse
 \COstart@action
 \@input{\[log in to unmask]\COextension}
 \@nobreakfalse
 \endgroup
}

\DeclareDocumentCommand{\contentsobject}{mmmmmmm}
  {\UseInstance{contentsobject}{#3}{#1}{#2}{#4}{#5}{#6}{#7}}

\DeclareDocumentCommand{\ABtableofcontents}{o}
  {\IfNoValueTF{#1}
      {\UseInstance{processcontents}{maintoc}{\NoValue}}
      {\UseInstance{processcontents}{chaptertoc}{#1}}
  }

\DeclareInstance{processcontents}{maintoc}{AB}
  {file-extension = toc,
   contents-depth = 2}

\DeclareInstance{processcontents}{chaptertoc}{AB}
  {file-extension = toc,
   contents-depth = 3,
   heading        = \subsection*}

\DeclareInstance{contentsobject}{part}{AB}
 {pre-v-action     = \DelayEvaluation{\endgraf\addvspace{4ex plus 4pt}},
  title-format     = \textsc{#1},
  number-format    = \textsc{Part~#1:\hfil},
  pnum-format      = {},
  leaders-action   = ~,
  number-width     = \DelayEvaluation{4.5em}}

\DeclareInstance{contentsobject}{chapter}{AB}
 {pre-v-action     = \DelayEvaluation{\endgraf\addvspace{1.5ex plus 1pt}},
  title-format     = #1\IfNoValueF{#2}{\comma\space\textit{#2}},
  number-format    = #1.\hfil,
  pnum-format      = \hfil#1,
  leaders-action   = .,
  leaders-sep      = \DelayEvaluation{0.5em},
  number-width     = \DelayEvaluation{2.5em}}

\DeclareInstance{contentsobject}{section}{AB}
 {object-decls     = \small,
  title-format     = #1,
  number-format    = #1.\hfil,
  pnum-format      = \hfil#1,
  leaders-action   = .,
  leaders-sep      = \DelayEvaluation{0.5em},
  number-width     = \DelayEvaluation{1em}}

\begin{document}

\ABtableofcontents

\ABtableofcontents[3]

\stop

=== test.toc ===

\contentsobject {1}{1}{part}{A}{Model Theory}{\NoValue}{1}
\contentsobject {2}{2}{chapter}{\NoValue}{Guide to Part A}{\NoValue}{3}
\contentsobject {3}{2}{chapter}{A.1}{An introduction to first-order logic}{Jon
Barwise}{5}
\contentsobject {4}{3}{section}{1}{Foreword}{\NoValue}{6}
\contentsobject {5}{3}{section}{2}{How to tell if you are in the realm of
first-order logic}{\NoValue}{6}
\contentsobject {6}{3}{section}{3}{The formalisation of first-order
logic}{\NoValue}{17}
\contentsobject {7}{3}{section}{4}{The Completeness Theorem}{\NoValue}{22}
\contentsobject {8}{3}{section}{5}{Beyond first-order logic}{\NoValue}{41}
\contentsobject {9}{3}{section}{\NoValue}{References}{\NoValue}{45}
\contentsobject {10}{2}{chapter}{A.2}{Fundamentals of model theory}{H.\ Jerome
Keisler}{47}
\contentsobject {4}{3}{section}{1}{Introduction}{\NoValue}{48}
\contentsobject {4}{3}{section}{2}{Theories}{\NoValue}{49}
\contentsobject {4}{3}{section}{3}{Digrams and compactness}{\NoValue}{57}
\contentsobject {4}{3}{section}{4}{L\"owenheim-Skolem theorems}{\NoValue}{63}
\contentsobject {4}{3}{section}{5}{Recursively saturated models}{\NoValue}{69}
\contentsobject {4}{3}{section}{6}{Large and small models}{\NoValue}{73}
\contentsobject {4}{3}{section}{7}{Stable theories}{\NoValue}{82}
\contentsobject {4}{3}{section}{8}{Model-theoretic forcing}{\NoValue}{89}
\contentsobject {4}{3}{section}{9}{Infinite formulas and extra
quantifiers}{\NoValue}{95}
\contentsobject {9}{3}{section}{\NoValue}{References}{\NoValue}{101}
\contentsobject {11}{2}{chapter}{A.3}{Ultraproducts for algebraists}{Paul C.\
Eklof}{105}
\contentsobject {12}{1}{part}{B}{Set Theory}{\NoValue}{315}
\contentsobject {13}{2}{chapter}{\NoValue}{Guide to Part B}{\NoValue}{317}
\contentsobject {14}{2}{chapter}{B.1}{Axioms of set theory}{J.\ R.\
Schoenfield}{321}