SEKE 2012 Proceedings - Knowledge Systems Institute

VII. DISCUSSION
Our method checks configuration files based on the configuration
model and deals with syntax error and semantic
error. As the result which is shown in Fig. 6, one error is
detected. The cause of the error is that using database is not
configured although address book application needs database.
The important part is that even if configuration files do not
have error, errors occur when configuration files are used
in order to perform application. Checking semantic error of
configuration files statically is one merit of our method.
It is not easy to understand syntax and constraints of
configuration files although those are explained in manuals. In
our method, syntax and constraints are described structurally
by using the feature diagram. Besides, checking configuration
files based on constraints of the feature diagram becomes
possible. We consider that a method which organizes configuration
files using the feature diagram is effective.
Configuration model describe five patterns of configuration
file syntax. These patterns are extracted from syntax
of httpd.conf, but the patterns do not cover all syntax. In
particular, 180 setting items are available for httpd.conf and
patterns cover 153 setting items. So, the patterns can deal with
85 percent of setting items of httpd.conf.
A configuration model may be changed when needed configuration
files are changed because of change of application,
or candidates and constraints of configuration file description
are changed. This change means adding or replacing pattern
descriptions and is not difficult. Users or administrators only
have to follow the notations of the feature diagram.
Syntax checkers are enough to check syntax error because
each syntax checker is specialized in specific configuration
files. However, syntax checkers are not enough to check
semantic error because semantic error is not a target. We focus
on relations between requirements and configuration files, and
model those relations in order to check.
VIII. RELATED WORK
A method which checks configuration files based on rules is
proposed [7]. Rules mean dependencies between modules or
formats for data exchange. A method which checks validity
of parameters of configuration files is proposed [8]. In this
method, size, range and dependency of parameters are identified
as constraints, and parameters are checked based on them.
Our method takes the similar approach which was proposed
in [7] [8]. Errors which can be detected by those methods
depend on rules, constraints or model. That is to say, it is
important what condition use to detect errors. On the other
hand, using rules and constraints is not suitable for checking
semantic errors because it is difficult to deal with requirements.
A method which deals with dependencies of configuration
attributes of software stack is proposed [6]. Authors proposed
Configuration Map (CM) which specifies dependencies and
order of configuring of configuration attributes, and relations
between configuration attributes and errors. By using CM,
managing configuration attributes becomes easily and CM is
effective for troubleshooting. As shown in [6], it is helpful
to model complexity in order to make configuration. Our
method deals with not only variability of configuration files
but variability of application, and models them in order to
make suitable configuration files for application.
An automatic generation method for configuration files of
web system which consists of Web server, application server
and database, is proposed [10]. In this method, configuration
files are generated by some scripts based on templates and
parameters are detected using heuristic algorithm. Automatic
generation is also a support method to make configuration files.
However, it is not easy to specify combinations of setting item
and parameter because descriptions of configuration files have
flexibility. Therefore, our method checks configuration files
which are made manually instead of automatic generation of
configuration files.
IX. CONCLUSION
In this paper, we proposed a method which manages variability
of configuration files in order to prevent errors of configuration
files. We define the configuration file model which
organizes basic elements of configuration files and relations
of them. Besides, a configuration file model is described by
using the feature diagram in order to check.
Verifying configuration files is important as well as software
because the complexity and size of configuration files
are increasing drastically. Some applications have their own
syntax checkers for configuration files of them. However, only
checking syntax is not sufficient to ensure that what we want
to configure the applications is correctly described in the
configuration files. Thus, in our approach, requirements for
the configuration files are modeled as a configuration model
and check whether they meet the requirements or not.
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