diff --git a/source/presenter.dtx b/source/presenter.dtx
index 837ddef..688037d 100644
--- a/source/presenter.dtx
+++ b/source/presenter.dtx
@@ -291,7 +291,9 @@
 %    \end{macrocode}
 % \end{macro}
 % \begin{macro}{foreground/sectioning}
-% Handle the sectioning logic.
+% Handle the sectioning logic. Use in pair with \texttt{foreground/headline}.
+% The call of \cs{pretsec_register_name_title:nn} is required for every
+% implementation code of this object type.
 % \begin{arguments}
 %   \item the name of sectioning.
 %   \item the content of the sectioning title.
diff --git a/source/pretfg.dtx b/source/pretfg.dtx
index 39f5f0a..41a71b6 100644
--- a/source/pretfg.dtx
+++ b/source/pretfg.dtx
@@ -171,15 +171,14 @@
   {
     \AssignTemplateKeys
     \group_begin:  
-      \l_@@_fg_headline_style_tl
-      \tl_use:N \l_@@_fg_headline_title_tl
+      \l_@@_fg_headline_style_tl \pretsec_cur_title:
     \group_end:
     \hfil
   }
 \DeclareTemplateCode { foreground / sectioning } { default } { 2 }
   { }
   {
-    \tl_set:Nn \l_@@_fg_headline_title_tl { #2 }
+    \pretsec_register_name_title:nn { #1 } { #2 }
   }
 \tl_new:N \l_@@_fg_footline_style_tl
 \DeclareTemplateCode { foreground / footline } { default } { 0 }
@@ -219,7 +218,7 @@
   {
     \AssignTemplateKeys
     \group_begin:
-    \pretsec_get_parent_child_title:NN \l_tmpa_seq \l_tmpb_tl
+    \pretsec_get_stack_parent_child_title:NN \l_tmpa_seq \l_tmpb_tl
     \seq_if_empty:NTF \l_tmpa_seq
       {
         \l_@@_fg_headline_child_style_tl \l_tmpb_tl
@@ -239,7 +238,8 @@
 \DeclareTemplateCode { foreground / sectioning } { dual } { 2 }
   { }
   {
-    \pretsec_push_name_title:nn { #1 } { #2 }
+    \pretsec_register_name_title:nn { #1 } { #2 }
+    \pretsec_push_stack_name_title:nn { #1 } { #2 }
   }
 \tl_new:N \l_@@_fg_footline_style_tl
 \DeclareTemplateCode { foreground / footline } { dual } { 0 }
@@ -259,7 +259,7 @@
 % \paragraph{\pkg{cascade} style.}
 %
 % Almost the same as \pkg{dual} style. But all the parent nodes are displayed.
-% Since the parent sequence returned from \cs{pretsec_get_parent_child_title:NN}
+% Since the parent sequence returned from \cs{pretsec_get_stack_parent_child_title:NN}
 % is in the reversed order, when displaying it, reverese the sequence first.
 %
 %    \begin{macrocode}
@@ -277,7 +277,7 @@
   {
     \AssignTemplateKeys
     \group_begin:
-    \pretsec_get_parent_child_title:NN \l_tmpa_seq \l_tmpb_tl
+    \pretsec_get_stack_parent_child_title:NN \l_tmpa_seq \l_tmpb_tl
     \seq_if_empty:NTF \l_tmpa_seq
       {
         \l_@@_fg_headline_child_style_tl \l_tmpb_tl
@@ -299,7 +299,8 @@
 \DeclareTemplateCode { foreground / sectioning } { cascade } { 2 }
   { }
   {
-    \pretsec_push_name_title:nn { #1 } { #2 }
+    \pretsec_register_name_title:nn { #1 } { #2 }
+    \pretsec_push_stack_name_title:nn { #1 } { #2 }
   }
 \tl_new:N \l_@@_fg_footline_style_tl
 \DeclareTemplateCode { foreground / footline } { cascade } { 0 }
diff --git a/source/pretsec.dtx b/source/pretsec.dtx
index 09b1051..c0b2d74 100644
--- a/source/pretsec.dtx
+++ b/source/pretsec.dtx
@@ -98,8 +98,54 @@
 %
 % \subsection{Sectioning Title Management}
 %
-% \pkg{pretsec} uses two stacks for storing both the level and the title info
-% of sectioning.
+% \subsubsection{Required}
+%
+% \emph{Every sectioning implementation} requires to register the current
+% sectioning name and the sectioning title by calling
+% \cs{pretsec_register_name_title:nn} for the communication with other
+% components of \presenter{}. 
+%
+% \begin{variable}[int]{\g_@@_cur_name_tl, \g_@@_cur_title_tl}
+% These private variables store the metadata of current sectioning name or
+% current sectioning title.
+%    \begin{macrocode}
+\tl_new:N \g_@@_cur_name_tl
+\tl_new:N \g_@@_cur_title_tl
+%    \end{macrocode}
+% \end{variable}
+% \begin{macro}{\pretsec_register_name_title:nn}
+% Register the current sectioning name and sectioning title to the \presenter{}
+% sectioning mechanism, which is required to be called for \emph{every
+% sectioning implementation code}.
+% \begin{arguments}
+%   \item sectioning name token list
+%   \item sectioning title token list
+% \end{arguments}
+%    \begin{macrocode}
+\cs_new:Npn \pretsec_register_name_title:nn #1#2 {
+  \tl_set:Nn \g_@@_cur_name_tl  { #1 }
+  \tl_set:Nn \g_@@_cur_title_tl { #2 }
+}
+%    \end{macrocode}
+% \end{macro}
+% \begin{macro}{\pretsec_cur_name:, \pretsec_cur_title:}
+% Macro of current sectioning name or the current sectioning title.
+%    \begin{macrocode}
+\cs_new:Nn \pretsec_cur_name:  { \g_@@_cur_name_tl  }
+\cs_new:Nn \pretsec_cur_title: { \g_@@_cur_title_tl }
+%    \end{macrocode}
+% \end{macro}
+%
+% \subsubsection{Stack-Based}
+%
+% For the scenario of getting the route from the root to the leaf of the
+% current sectioning position of the outline tree, it is efficient to use a
+% stack-based solution to keep track of the sectioning.
+% Since the sectioning level usually doesn't exceed 5 (subparagrah), the stack
+% depth will also no more than 5, which makes possible to process on the fly
+% without additional file storage.
+% \pkg{pretsec} solution uses two stacks for storing both the level and the
+% title info of sectioning.
 %
 % \begin{figure}[H]
 %   \newcommand{\docseqitem}[1]{\framebox[6em]{\vphantom{girl}#1}}
@@ -113,6 +159,26 @@
 %   \end{tabular}
 % \end{figure}
 %
+% The current implemetation is as follows:
+% \begin{itemize}
+%  \item If the \meta{name} is \texttt{star}, then set \cs{g_@@_star_mark_bool}
+%        to \texttt{true} and store the \meta{title} to the temporary storage
+%        \cs{g_@@_star_title_tl}.
+%        Since the current implementation of \cs{@ssect} cannot be aware of what
+%        level of sectioning for the starred version of those sectioning
+%        commands.
+%  \item If the \meta{name} is \texttt{part}, then clear two stacks
+%        \cs{g_@@_lv_seq} and \cs{g_@@_title_seq}.
+%        Since the current implementation of \tn{part} cannot receive the
+%        parameter of \meta{part title} and will do the special typesetting
+%        distinguished from other sectioning commands.
+%  \item Otherwise, pop the stacks until \meta{current level} $<$
+%        \meta{stack-top level}, at the moment, the items in the stacks are the
+%        ancestors of the current. In the end, push the current item to the
+%        stacks. Now, the top of the stack is the child. Be aware, the ancestors
+%        are in a reversed order in the sequence (the leftmost is the lowest).
+% \end{itemize}
+%
 % \begin{texnote}
 %
 % In the current implementation of \file{l3seq.dtx}, for the sequence of length
@@ -163,14 +229,14 @@
 %    \end{macrocode}
 % \end{variable}
 %
-% \begin{macro}{\pretsec_push_name_title:nn}
+% \begin{macro}{\pretsec_push_stack_name_title:nn}
 % Store the title at the level of sectioning name.
 % \begin{arguments}
 %   \item sectioning name
 %   \item title
 % \end{arguments}
 %    \begin{macrocode}
-\cs_new:Npn \pretsec_push_name_title:nn #1#2 {
+\cs_new:Npn \pretsec_push_stack_name_title:nn #1#2 {
   \tl_if_eq:nnTF { #1 } { star }
   {
     \bool_set_true:N \g_@@_star_mark_bool
@@ -207,14 +273,14 @@
 %    \end{macrocode}
 % \end{macro}
 %
-% \begin{macro}{\pretsec_get_parent_child_title:NN}
+% \begin{macro}{\pretsec_get_stack_parent_child_title:NN}
 % Get the parent title sequence (lowest is in the first) and the child title.
 % \begin{arguments}
 %   \item parent nodes sequence variable in bottom-up (reversed) order
 %   \item child node token list variable
 % \end{arguments}
 %    \begin{macrocode}
-\cs_new:Npn \pretsec_get_parent_child_title:NN #1#2 {
+\cs_new:Npn \pretsec_get_stack_parent_child_title:NN #1#2 {
   \seq_clear:N #1
   \tl_clear:N #2
   \bool_if:NTF \g_@@_star_mark_bool
@@ -233,29 +299,6 @@
 %    \end{macrocode}
 % \end{macro}
 %
-% \begin{macro}{\pretsec_get_cur_name:N}
-% Get the current sectioning name.
-% NOTICE: when the sequence \cs{g_@@_lv_seq} is empty, according to the
-%         current algorithm of \cs{pretsec_push_name_title:nn}, it is regarded as
-%         \texttt{part}. A reasonable explanation about the scenario where no
-%         sectioning command has been issued at the beginning of the document is
-%         that it is in Part 0 of this document.
-% \begin{arguments}
-%   \item output token list variable of current sectioning name
-% \end{arguments}
-%    \begin{macrocode}
-\cs_new:Npn \pretsec_get_cur_name:N #1 {
-  \bool_if:NTF \g_@@_star_mark_bool
-    { \tl_set:Nn #1 { star } }
-    {
-      \seq_get:NNTF \g_@@_lv_seq \l_tmpb_int
-        { \pretsec_get_lv_name:nN { \l_tmpb_int } #1 }
-        { \tl_set:Nn #1 { part } }
-    }
-}
-%    \end{macrocode}
-% \end{macro}
-%
 % \iffalse
 %</package>
 % \fi