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[u/philim/db2osl_thesis.git] / program_interface.tex
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28b54c67 1\section{Interface and usage}
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2\label{interface}
3This section describes the interface to the operating system and the user interface.
4For information on programming interfaces, see section \fullref{arch}.
5
6\subsection{User interaction and configuration}
7\subsubsection{Basic usage}
28b54c67 8\label{basic}
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9Currently, the only user interface of \myprog{} is a command-line interface.
10Since the program is supposed to bootstrap the OBDA Specification automatically and
11thus there is little interaction, but a lot of output, this was considered ideal.
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12Basically, one invocation of \myprog{} will initiate the automatic, non-interactive
13bootstrapping of exactly one \osl{} specification written to the standard output,
14a behavior which can be modified via command-line arguments.
c31df1ed 15Because of its ability to write to the standard output (which is also the default
28b54c67 16behavior), it is easy to pipe the output of \myprog{} directly into a program that
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17handles it in a Unix-/POSIX-like fashion TODO:
18\codepar{db2osl myserver.org | osl2onto myserver.org}
19
20(supposed \name{osl2onto} is a tool that reads an \osl{} specification from its
21standard input and uses it to bootstrap an ontology from the database
22specified on its command line).\\
23This scheme is known as ``filter-pattern'' TODO.
24
25By inserting additional ``filters'', the bootstrapping process can be customized
26without changing any of the involved programs:
28b54c67 27\codepar{db2osl mydatabase.org | customize\_spec.sh | osl2onto mydatabase.org}
c31df1ed 28
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29(supposed \name{customize{\scriptsize \_}spec.sh} is a shell script that modifies
30a given \osl{} specification in the way the user desires).
c31df1ed 31
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32\subsubsection{Configuration via command-line arguments}
33The behavior of \myprog{} itself can be adjusted via command-line arguments (only).
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34The syntax for their application follows the POSIX standard TODO.
35Most features can be configured via short options (as, for example, \code{-P}).
36To allow for enhanced readability of \myprog{} invocations, each feature can (also)
37be configured via a long option (like \code{\textendash\textendash password}).
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38The utilization of configuration files was considered, but for the time being
39seen as unnecessary complicating
40while not addressing any real difficulties.
c31df1ed 41
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42The command-line arguments \myprog{} currently supports are
43described in table \ref{if_tbl_arguments_desc},
44their default values are listed in table \ref{if_tbl_arguments_def}.
45There is currently no switch to set the output format, since the only supported
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46output format, besides \osl{}, is a low-level output format for debugging purposes.
47Because of this and since the change that has to be made in the source code to enable it
48only involves changing one token, it was preferred not to offer a command-line option
28b54c67 49for this, to not unnecessarily complicating the command-line interface for the
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50normal, non-debugging, user.
51
52\begin{table}[]\begin{center}
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53 \begin{tabular}{p{4.9cm}|p{11.1cm}}
54 Option(s) & Description, taken from the help page of \myprog{}\\
c31df1ed 55 \hline
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56 \code{\textendash\textendash database}, \code{-d} & database name (\name{Java} regular expression) databases have to match to be processed; see also: \code{\textendash\textendash loose-database-match}\\
57 \code{\textendash\textendash echo-password} & echo input when prompting for SQL password -- must be specified before \code{\textendash\textendash password-prompt} to get effective\\
58 \code{\textendash\textendash help}, \code{-h, } & show this help and exit\\
59 \code{\textendash\textendash interactive}, \code{-i} & be interactive when chosing database\\
60 \code{\textendash\textendash login}, \code{-L} & SQL login\\
61 \code{\textendash\textendash loose-database-match} & if no database matching the regex specified with \code{\textendash\textendash database} is found on the given server and \code{\textendash\textendash interactive} is not specified for this job, use some other database\\
62 \code{\textendash\textendash osl-header} & use the specified custom (non-standard) OSL header, implies \code{\textendash\textendash remote-osl-header} (to import no header, specify the empty string)\\
63 \code{\textendash\textendash output-file}, \code{-o} & use the specified output file (for the standard output, specify ``-'')\\
64 \code{\textendash\textendash password}, \code{-P} & SQL password; use \code{\textendash\textendash password-prompt} to get a password prompt (if you do both, the password set via this switch will be ignored)\\
65 \code{\textendash\textendash password-prompt}, \code{-p} & prompt for SQL password; a password set via \code{\textendash\textendash password} is ignored\\
66 \code{\textendash\textendash remote-osl-header}, \code{-R} & don't use hard-coded version of the OSL header for verification\\
67 \code{\textendash\textendash remote-test} & try to retrieve a database schema from a hard-coded list of servers and take the first one successfully retrieved (and accepted, when \code{\textendash\textendash interactive} is given; note: give a dummy server if you want to do a test besides other jobs)\\
68 \code{\textendash\textendash test} & use hard-coded test database schema, ignore given servers (note: give a dummy server if you want to do a test besides other jobs)\\
c31df1ed 69 \end{tabular}\\
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70 \caption{Command-line arguments in \myprog{} -- descriptions}
71 \label{if_tbl_arguments_desc}
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72 \end{center}\end{table}
73
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74\begin{table}[]\begin{center}
75 \begin{tabular}{l|l}
76 Option(s) & Default value\\
77 \hline
78 \code{\textendash\textendash database, -d} & \code{.*}\\
79 \code{\textendash\textendash echo-password} & \code{false}\\
80 \code{\textendash\textendash help, -h, } & \code{false}\\
81 \code{\textendash\textendash interactive, -i} & \code{false}\\
82 \code{\textendash\textendash login, -L} & \code{anonymous}\\
83 \code{\textendash\textendash loose-database-match} & \code{false}\\
84 \code{\textendash\textendash osl-header} & \code{<empty string>}\\
85 \code{\textendash\textendash output-file, -o} & \code{-}\\
86 \code{\textendash\textendash password, -P} & \code{<empty string>}\\
87 \code{\textendash\textendash password-prompt, -p} & \code{false}\\
88 \code{\textendash\textendash remote-osl-header, -R} & \code{false}\\
89 \code{\textendash\textendash remote-test} & \code{false}\\
90 \code{\textendash\textendash test} & \code{false}\\
91 \end{tabular}\\
92 \caption{Command-line arguments in \myprog{} -- default values}
93 \label{if_tbl_arguments_def}
94 \end{center}\end{table}
95
96The sole invocation of \code{db2osl}, without any arguments, does not initiate any
97processing but displays the usage directions instead, in addition to an error message
98pointing out the missing server argument.
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99
100\subsubsection{Multiple bootstrapping operations or multiple servers}
28b54c67 101To perform multiple bootstrapping operations with only one invocation of \myprog{},
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102it is sufficient to concatenate the command-line arguments for each operation,
103separated by blanks, to get the final command line.
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104However, when combining a test job with other operations, some arbitrary string
105has to be inserted as dummy server to allow distinguishing the different jobs
106and assigning each command-line argument to the appropriate job.
c31df1ed 107
28b54c67 108Likewise, to check several servers in order for the database to be used
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109for one bootstrapping operation, these servers have to be concatenated,
110separated by blanks.
111Again, the distinction of the different bootstrapping jobs has to be possible,
112so all but the first operation have to have at least one command-line argument
28b54c67 113that signals the beginning of a new job definition
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114(which is no practical problem, since to enforce this, a default argument simply
115can be stated explicitly without changing the behavior of the invocation).
116
117All settings are configured per operation, so, when using a shell that separates batched
118commands by `;',
119\codepar{db2osl \textendash\textendash database employees \textendash\textendash
120 password itsme sql.myemployer.com\\
121 \textendash\textendash database test myserver.org backup.myserver.org}
122is equivalent to
123\codepar{db2osl \textendash\textendash database employees \textendash\textendash
124 password itsme sql.myemployer.com;\\
125 db2osl \textendash\textendash database test myserver.org backup.myserver.org}
126
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127Thus, a parameter defined for one operation (like the password
128in the example) will have no effect on other operations.
129This ensures that typical errors are prevented when merging several invocations
130of \myprog{} into one (or vice versa)
131and allows for a straight-forward, comprehensive and clean implementation.
132
133\subsubsection{Advanced modifications}
134Since \osl{} specifications are plain text files, a user can edit them in any desired
135text editor if he wants to change them in ways that go beyond the functionality
136\myprog{} provides or that can be achieved by scripts or programs modifying their
137input automatically.
138Because of \osl{} being defined to be a subset of \name{OWL} (see the specification
139of \osl{} in section \ref{oslspec}), he can thereby take advantage of editors
140supporting syntax highlighting or other features making the handling of
141the respective \name{OWL} serialization more comfortable.
142
143Moreover, every common ontology editor can be used to edit the generated \osl{}
144specification automatically or manually.
145Doing so, care has to be taken to make the ontology remain a conforming \osl{}
146specification. However, since the restrictions imposed by \osl{} are rather
147small and intuitive, this is easily achieved.
148Furthermore, upcoming tools supporting \osl{} (see section \fullref{future}) are very
149likely to be able to check their input for conformity with the \osl{} definition.
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150
151\subsection{Integration into systems}
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152Besides the use cases described in section ``\nameref{basic}'',
153there are many other ways in which \myprog{} can be used.
154For example, a database can be periodically checked for changes that make a
155re-bootstrapping necessary:
156\codepar{db2osl -d mydb myserver.org | sha256sum >oldsum\\
157 cp oldsum newsum\\
158 while diff oldsum newsum; do\\
159 \ind sleep 3600\ \ \# wait 1 hour\\
160 \ind db2osl -d mydb myserver.org | sha256sum >newsum\\
161 done\\
162 rm oldsum newsum\\
163 \# notify web admin via e-mail:\\
164 mutt -s "Re-bootstrapping necessary" web-admin@myserver.org}
165
166Another possible example is the integration of \myprog{} into a shell script
167that bootstraps all databases on a server:
168\codepar{regex=\textquotesingle(?!\$).*\textquotesingle\ \ \# accept all nonempty database names first\\
169 while db2osl -d "\$regex" -o spec myserver.org; do\\
170 \ind dbname="\`{} sed -ne \textquotesingle/xmlns:ont/ \{ s|.*/||; s|\#"||p \}\textquotesingle\ spec \`{}"\\
171 \ind mv spec "\$dbname".osl\\
172 \ind \# don't use this database a second time:\\
173 \ind regex="\`{} printf \%s "\$regex" | sed -e "s,\textbackslash\textbackslash\textbackslash\textbackslash\$,\$|\$dbname\$," \`{}"\\
174 done}
175
176Newer versions than version 1.0 described here provide a command-line parameter
177\code{-a} (or, alternatively, \code{\textendash \textendash all)}
178which makes \myprog{} bootstrap \emph{all} databases matching the given
179regular expression.
180However, using this approach, all bootstrapped specifications will be output
181to one single file.
182
183Since the programming language used to implement \myprog{} is \name{Java},
184it is possible to deploy it on all platforms offering the
185\name{Java Runtime Environment} TODO.
186Additionally, it is possible to deploy it as a Web application TODO.
187
188To simplify integration on the code level, the architecture of \myprog{} was
189designed to be highly modular and to cleanly separate code with different areas of
190responsibility into different packages
191(for details about the structuring of \myprog{}, see section \fullref{arch}).
192This modularity, besides facilitating understanding the code,
193allows for a high degree of code reusability.
194
195For example, the packages \code{database}, \code{osl} and \code{specification}
196can be reused in other programs with little or no changes --
197the biggest change involves combining the database schema retrieval with the
198user interface of the new program to provide control over the retrieval process
199when reusing the \code{database} package
200(to do this, three method calls have to be replaced).
201%However, the \code{osl} package heavily depends on the \code{specification} package.
202If the accruing information shall be used in another way than being output or logged,
203this of course has to be implemented.
204If not, it is sufficient to replace the used \code{Logger} object by anohter one
205providing the desired behavior, since the \code{Logger} class is part of the
206\name{Java} API and widely used TODO.
207This is a good example of how using well-known and commonly used classes can
208greatly improve modularity and reusability.