\section{Encountered Problems}
\label{encountered_problems}

PaWS implementation process encountered several problems and bugs:

\begin{itemize}

\item {\bf Perserving the consistency between output of Tpips and Pyps
    computations}
  
  At the beginning operations over prepared examples were performed
  with Tpips script, while user provided code was handled by
  Pyps. Also supplied example after user modification were analyze or
  transformed with Pyps. That was causing a lack of consistency in the
  output - Pyps in the basic level is working with the default values,
  while in the Tpips script other settings can be used as well. Also
  the style of the output pproduced by the Tpips and Pyps is slightly
  different. To provide completely consistent output all operation in
  the tools mode, for basic and for advanced levels, are performed by
  Pyps. Tpips is used in the demonstration mode, which needs script with a
  set of well-defined operations, wnot modifiable by a user.
  
  \item {\bf Validation of the Pyps code}
  
    PIPS and Pyps are constantly in the development process. That can
    cause that the Pyps code used for the PaWS operations might
    require changes according to the Pyps changes. To minimize
    problems resulting from this, such as getting a wrong output or
    being unable to perform operations, all of the Pyps code used in
    PaWS is moved to the \emph{validation} directory, where it can
    undergo validation process and be easily changed if it is needed.
  
  \item {\bf Updating PIPS automatically}
  
    This problem is related to the previous one - PIPS framework,
    which is still changing, has to be updated frequently, to let the
    users try the newest version of it. With automatic update, there
    might be a problem when the current version of PIPS contains bugs or
    is even broken. To avoid such situation, PIPS updates are controlled
    manually.
  
  \item {\bf Provide concurrent access}
  
    The Pylons framework creates a new thread for each user request. This
    might cause problems with Pyps, which requires a new process. Pyrops
    (see Section \ref{other_technologies}) module, which separates
    Pyps workspaces, was the solution of this problem. Pyrops is also
    under development (it is build in Pyps).
  %% bug with sharing workspaces?
  
  \item {\bf Overloading server}
  
    Too many user requests might overload the server. Problem has not
    been solved for the time being.
  
  \item {\bf Points to the documentation}
  
    User should have information about the PIPS properties and
    analyses which might be used in the advanced level of the tools
    mode. The best option to provide it is to link them to the proper
    sections in the PIPS online documentation
    (\url{http://cri.ensmp.fr/pips/pipsmake-rc.htdoc/}). The problem
    is to extract the exact addresses of the sections, whereas they
    are generated randomly and changed during the documentation
    compilation. Currently information about the PIPS settings
    (properties, analyses and phases) is provided by the PaWS
    description files.

\end{itemize}