SEKE 2012 Proceedings - Knowledge Systems Institute

means patterns which are shown in section V.A. In particular,
predicates, where constraints are described, are checked.
Correction method of feature selection compares causes of
errors with chosen features in order to detect causes of errors.
The Alloy Analyzer automatically searches that what features
should be chosen based on each correction method.
Consistency checking method for correspondence relations
between requirement model and config model checks whether
an instance of config model satisfies an instance of requirement
model. This check is implemented by set operators of Alloy.
In particular, Alloy checks whether a set of combination of
setting item and parameter which is required by an instance
of requirement model is subset of an instance of config model.
Correction method of correspondence relations also searches
instances. The Alloy Analyzer searches an instance of config
model which includes the existing instance and features which
are needed for correction.
VI. EXPERIMENT
In the experiment, we apply our method to a Web application
system which consists of an application and an execution
environment. We deal with an address book application as
application. Execution environment consists of some software,
and each software use configuration file.
A. Preparing for checking
1) Analysis of application: An address book application
has some functions such as showing, registration and editing.
Those functions have variations. There are some methods for
data registration. For example, files which contain data are
uploaded to a server, or users input data into a form on a web
page. Files or database are used in order to save data. Editing
data is data correction or deleting. In this way, functions
of application are analyzed. Analysis of configuration file
description for operation of each requirement is discussed later.
2) Analysis of configuration files: At least three kinds
of software, web server, server-side programming language
environment, and database server are needed. So, each of
software’s configuration file should be analyzed. For web
server, we assume that Apache is used. Basic configuration
for web server is needed. Besides, configuration for server-side
programming or cgi is needed. For server-side programming
environment, we assume that PHP is used. Configuration for
connecting to database server is needed. For database server,
we assume that PostgreSQL is used. Basic configuration for
database server is needed.
3) Analysis of correspondence relations: Which combinations
of setting item and parameter are needed for executing
each function is analyzed. Web server is needed in order to
show contents of address book, CGI or PHP are needed in
order to execute functions such as registration and deleting.
Database server is needed in order to save data.
4) Describing configuration model: A configuration model
is described based on analysis results. The configuration model
is shown in Fig. 4. The configuration model has to be described
in Alloy in order to check it. However, Alloy description is
omitted this time.
B. Consistency checking
In our method, feature diagrams and correspondence relations
between instances of them are checked separately.
Because, it makes no sense to check correspondence relations,
if there is no instance of requirement model or config model.
1) Feature diagram: We choose some features from the
requirement model and check it using the Alloy Analyzer. The
result is shown in Fig. 5.
Fig. 5.
Result of Checking (Feature diagram)
In Fig. 5, “field configuration” shows set of chosen features.
“field validity” shows presence or absence of error. “field
inconsistent” shows causes of error and correction methods.
“field corrected” shows a candidate of corrected chosen features.
As the result of this checking, errors are detected, and
causes of errors and correction methods are shown.
2) Correspondence relations: We assume that there are
instances of requirement model and config model. A result
of checking of correspondence relations is shown in Fig. 6.
Fig. 6.
Result of Checking (Correspondence relation)
In Fig. 6, “field Ains E” shows what features are required
by the instance of requirement model. “field diff” shows that
what features are lacking in the instance of config model.
“field validity” shows presence or absence of error. As the
result of checking, there is one error. The error means that
“PostgreSQL” is not included in the instance of config model
although the application requires database. So, correction
method applies to the instance of config model. The result
of correction is shown in Fig. 7.
Fig. 7.
A Candidate of Corrected Instance
A candidate of corrected instance is shown in left side of
Fig. 7. In right side of Fig 7, causes of inconsistencies and
correction methods of them are also shown.
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