Dissertaç ˜ao de Mestrado Mestrado em Engenharia Informática Jo ...

1. INTRODUCTION 1.3. Problem Approach
1.3 Problem Approach
Section 1.2 identified two ways to configure applications in virtual appliances: pre and post-
installation. The pre-installation approach has no outstanding requirement and operates by
generating as many application packages as different required configurations for that applica-
tion, and does not allow for the re-configuration of an application in a practical fashion (i.e.,
without resorting to that application re-installation). On the other hand, the post-installation
approach requires previous knowledge of the software running inside the VA but, contrary
to the previous approach, each different configuration only requires a new configuration file
version, and allows for the practical re-configuration of an application. Given the benefits and
drawbacks of each approach, the post-installation approach requirement was found tolerable
and moreover, allows for better functionality than the pre-installation approach and, therefore,
SmART will follow this discipline.
The adopted approach operates by conducting a lexical analysis on an application’s con-
figuration files with the aim of extracting the relevant information for that application con-
figuration from them. This raises a significant requirement which says that the configuration
files must be in text format. A consequent implication of this requirement is that special for-
mats, like the Windows OS registry or binary files, may not be configurable using the approach.
However, there exist dedicated parsers for the treatment of those formats and these can be used
by the framework to provide support for the mentioned kinds of formats.
Still in the scope of the applications supported by SmART, Section 1.2.3 concluded that, at a
conceptual level, the structure of the configuration files expected to be found more regularly by
the tool can be reduced to three types: INI-like, XML-like and Apache-like. These three types were
already presented and implement three patterns: parameters, comments and blocks, besides
the patterns specific to a certain application. One way of tackling this problem is to reduce
the configuration files of any application to a generic structure, dettached from its application
specifics, which contains the relevant elements for its application configuration. This structure
can then be modified without any knowledge of the application to which it belongs. Once
altered, that structure is again converted to a configuration file in its original syntax, containing
the applied modifications.
1.4 Contributions
This dissertation contributions for the automatic application configuration are:
• Identification of commonalities amidst configuration files structures;
• Proposal of a framework for the rebuilding of configuration files of an application;
• Implementation of the proposed framework;
• Provision of the VIRTU project with a state-of-the-art and innovative tool for application
reconfiguration, independent of its vendor.
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