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

3. AN APPLICATION RECONFIGURATION FRAMEWORK 3.5. Modifying the Configuration File
3.5 Modifying the Configuration File
Despite not being part of this work, some possible ways to deal with the configuration file
modification theme were identified.
In the presence of a configuration file, structured in an XML document, one can either man-
ually modify it, using a regular text editor or a similar XML editor, or automatically modify it,
employing an XML script which applies the changes to a configuration file without the need
for any user intervention.
The first way does not ask for any special requirement, other than having a text editor at
hand, and therefore, consists on the easiest way to modify a configuration file in XML. On the
other hand, the second way requires a script to be previously built. This script may, neverthe-
less, be reusable and also allows for a completely automatic application configuration process.
However, one must first know how the generic syntax is structured in order to build a script
that operates on it.
Therefore, it is very important that all the files in generic syntax follow the same structure
and nomenclature, regardless of their original format. For example, assuming there is a script
which goes through an entire configuration file searching for the block “Network” to change
the “address” parameter value to “192.168.0.100”, it is vital that every file in generic syntax rep-
resents block parameter patterns in the same way (i.e., a generic syntax element called “Block”
with a “value” element assigned to it) so that the script recognizes those patterns when it sees
them. The same goes for anyone who wants to manually make that change. The person who
applies the modification should not be obliged to know multiple generic syntaxes for various
configuration file languages, but rather a homogeneous syntax which might slightly diverge
from language to language, depending on that language idiosyncrasies.
3.6 External Parser Addition
In response to the non-functional requirement in Section 3.1 which says that the user must be
able to add parsers built outside the tool, Section 3.3.1 indicates that the Parser Repository
implements the importParser method. This utility is especially useful when the user wants
to configure applications whose configuration files cannot be parsed by parsers created by
the chosen parser generator (e.g., binary files) or if the user already possesses a parser for a
configuration file.
Nevertheless, in order for an external parser to be added to the tool, it must implement
the interface defined in Listing 3.8. This interface solely defines one method, which is the one
called by the Configuration File Parser when parsing a file with an external parser.
Furthermore, the method must return the parsing statistics and the parsed blocks in generic
syntax.
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