\section{Avoidance of information saturation  in CE environments} \vspace{1ex}%\noindent
The  overall design process for a Combined Navigational System is
evidently multi-step, multi-team and multi-disciplinary (the
strengths), but it is iterative (a weakness).  Concurrent
Engineering for design is a strategy to ``fight against the
weakness by the strengths.''  Multiplicity of steps, teams and
working disciplines leads to the implication that these elements
give a more parallel structure of making design decisions. This
means that more portions of more objective information may become
available and concurring on decisions in the early design steps.
This can facilitate a drive to reduce re-work iterations  and  to
avoid them -- theoretically -- throughout the whole design
process, -- the latter would mean the ``ideal'' case of
right-first-time design solutions. Thus, CE approach transfers the
information ``center of mass'' towards the early stages of design
process. ``Front-loading'' is the given name of this approach in CE \cite{clark:1991}.


However,  failure to maintain a necessary order in the information
inputs from parallel multidisciplinary teams results in the
malfunction of this strategy. One way around this problem of
possible information saturation near to the outset of the design
process is to use the \textsl{Hierarchy of Conceptual Design}
(HCD) where the design\verb='=s  development is represented as
concepts of the design ordered by information type from the
subjective towards the objective \cite{king:2002}.

Adhering to the HCD model and mapping the above overall system
design process onto the so called \textsl{phase design cycle}
yields an aggregated representation of the same process in the
%summary 
aggregate Table~1 showing possible overlapping of phases and steps.


{
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\begin{table}
%%%%%%%table#1%%%%%%%%%

\setlength{\arrayrulewidth}{.5pt}
\begin{center}

\begin{tabular}{||>{\PBS\centering\hspace{0pt}}m{1cm}%
|>{\PBS\centering\hspace{0pt}}m{2.8cm}%
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|>{\PBS\centering\hspace{0pt}}m{1cm}||}
\hline
\multicolumn{4}{|c|}{Table~1. An aggregated representation of
the overall system design process} \\
\hhline{|t:==:t:==:t|}
 Phase \# &
 Name of phase &
 Phase result &
 Step \# \\
\hhline{|:==::==:|}%
 0 &
 Clarification of the problem &
 Initial design requirements: \linebreak Holistic-Concepts
 $\Rightarrow$ Viewpoint-Concepts &
 0 \\
\hhline{||--||--||}
 1 &
 Conceptual Design &
 Broad potential solutions based on the analysis of the
 problem:\linebreak
 Inventive-Concepts $\Rightarrow$ Precepts $\Rightarrow$
 Classical-Concepts &
 {1}\linebreak\raisebox{-4.5pt}{2} \\
\hhline{||--||- ||}
 2 &
 Embodiment &
 Identified and fixed major attributes of the product &
 \raisebox{2.5pt}{3}\linebreak\raisebox{-2.5pt}{4} \\
\hhline{||--||- ||}
 3 &
 Detail Design &
 Manufacturing specifications of the product &
 \raisebox{4.5pt}{5}\linebreak{6}\\
\hhline{||--||--||}
 4 &
 Experimental Product &
 Produced and bench tested experimental product &
 7\linebreak 8\linebreak 9 \\
\hhline{||--||--||}
 5 &
 Acceptance Test &
 Acceptance of the design &
 10\\
\hhline{|b:==:b:==:b|}

\end{tabular}

\end{center}
%%%%%%%table#1%%%%%%%%%
\end{table}
}

\begin{figure}\label{fig1}
\begin{center}
\input{fig1-SUN}
\caption{%
Integrated CAD/NAST system.
\textsl{Legend}:
1 -- Design requirement specification;
2 -- Assembly expert;
3~-- Overall design knowledge base;
4 -- Design instance library;
5 -- Cost and analysis expert;
6 -- Manufacturing expert;
7 -- A pool of reference (``truth'') models to be tested;
8 -- Procedural algorithms;
9 -- Algorithm expert (system);
10 -- Algorithm knowledge base;
11 -- Library of ``proper'' algorithms and parameter
numerical values;
12 -- The current reference (``truth'') model for analysis;
13 -- Automated simulation program generator including a set of design (simplified) models;
14 -- Simulation condition specification;
15 -- Simulation program runs;
16~-- Simulation results visualization and interpretation;
17 -- Evaluation and modification;
18 -- Consideration of another model from the selected pool;
19 -- The current model adjustment;
20 -- Simulation program refinement;
21 -- Simulation condition modification;
22 -- RESULT: acceptance of the design.%
}
\end{center}
\end{figure}%
