Minor change

[u/philim/db2osl_thesis.git] / program_functionality.tex

\section{Functionality}
\label{functionality}
As described in the introduction, the \myprog{} software basically is a program which
automatically derives an OBDA specification from a relational database schema,
which then can be used by other tools to drive the actual bootstrapping process.
Its functionality is described in the next section
(while leaving out self-evident features) and is then listed completely
in the section after that.

\subsection{Description}
The database schema is retrieved by connecting to an \name{SQL} database
and querying its schema information.
Parsing \name{SQL} specifications TODO or \name{SQL} dumps currently is not supported.
%Naturally, authentication on the \name{SQL} server is supported, also by
%interactively querying for passwords while hiding the typed input.
The databases to derive information from can be specified by regular expressions,
while there are also options to use other databases than specified or even
other database servers, taken from a list of hard-coded strings.
While these features may not seem to carry real benefit at the first glance,
they proved to be very useful for testing purposes, especially since the retrieval of a
database schema can take some time (see TODO).
For the same purpose, \myprog{} allows the processing of a hard-coded example database schema.

In addition to \osl{} output, a low-level output format containing information on all fields of
the underlying objects is supported, which is useful for debugging
(however, this feature has to be enabled via one slight change in the source code).
To allow for some customization, the insertion of an own \osl{} header is supported
(for more information on the \osl{} header, see the specification of the \osl{} language
in section \ref{oslspec}).
If the standard \osl{} header is used, it is by default loaded from a hard-coded copy,
so bootstrapping information from a database server running locally or from the hard-coded
example schema requires no Internet connection
(simply inserting the \code{owl:imports} statement of course would not anyway,
but the generated underlying ontology is always checked for consistency with the
\osl{} header to prevent the generation of invalid output).

The \myprog{} software can be used both in an interactive and in a non-interactive mode,
while skipping a database or a database server or aborting the entire bootstrapping process
is possible in either mode.
Multiple database servers can be specified for a bootstrapping operation,
which then are checked in order for a matching database,
allowing to make use of mirrors or fallback servers.
Additionally, multiple bootstrapping operations can be specified to be performed in sequence
with one invocation of \myprog{}, while all features and settings previously described
are enabled, disabled or set per operation.
Finally, a help text can be displayed which describes the usage of \myprog{} including the
description of all command-line arguments.

\subsection{Summary}
The functionality of the \myprog{} software can be summarized as follows:

\begin{itemize}
	\item Bootstrap one or more OBDA specifications from a database schema
	by connecting to an \name{SQL} database server
	\item Specify a custom port, login and password for the database server
	\item Ask for passwords interactively (before starting any bootstrapping
	operation), hide them if desired
	\item Specify database names by regular expressions
	\item Process an arbitrary database if the specified database
	could not be found or unconditionally
	\item Connect to a database server containing example databases
	without having to specify any further details
	\item Process a hard-coded example database schema
	without having to specify any further details
	\item Use the \osl{} format described in section \fullref{osl}
	or a detailed low-level format for output
	(the latter is for debugging purposes and has to be enabled
	in the source code)
	\item Write to standard output or to a file
	\item Insert a custom \osl{} header
	(see the specification of the OBDA Specification Language (\osl{})
	in section \ref{oslspec} for details)
	\item Consistency check against a custom \osl{} header
	\item Consistency check against the standard \osl{} header without internet connection
	\item Act interactively or non-interactively
	\item Skip currently retrieved database (and try next on server),
	skip current server or abort the overall process at any time, even in
	non-interactive mode
	\item Define multiple database servers to check in order for the specified database
	\item Specify multiple bootstrapping operations to perform in order
	\item Configure the features described in the above notes
	per bootstrapping operation
	\item Display a help text describing the usage of \myprog{},
	including the description of all command-line arguments
\end{itemize}