1.106 GPL (GNU General Public License)    
2.3/5 19
Provides a framework to help in validating the semantic content of configuration data.





Config::Model provides a framework to help in validating the semantic content of configuration data. The project can also be used to provide a semantic check of options of a complex program like mplayer or transcode.

For most complex software, configuration upgrade is a difficult task for most people. By using Config::Model, a software can provide a smooth upgrade path for their users.

How does this work ?

Using this project, a typical configuration validation tool will be made of 3 parts :

The user interface
The validation engine which is in charge of validating all the configuration information provided by the user.
The storage facility that store the configuration information

Don't we already have some configuration validation tools ?

You're probably thinking of tools like webmin. Yes, these tools exist and work fine, but they have their set of drawbacks.

Usually, the validation of configuration data is done with a script which performs semantic validation and often ends up being quite complex (e.g. 2500 lines for Debian's xserver-xorg.config script which handles xorg.conf file).

In most cases, the configuration model is expressed in instructions (whatever programming language is used) and interspersed with a lot of processing to handle the actual configuration data.

What's the advantage of this project ?

The Config::Model projects provide a way to get a validation engine where the configuration model is completely separated from the actual processing instruction.

The configuration model is expressed in a declarative form (i.e. a Perl data structure) which is always easier to maintain than a lot of code.

The declaration specifies:

the structure of the configuration data (which can be queried by generic user interfaces)
the properties of each element (boundaries, check, integer or string, enum like type ...)
the default values of parameters (if any)
mandatory parameters
the targeted audience (intermediate, advance, master)
on-line help (for ach parameter or value of parameter)
the level of expertise of each parameter (to hide expert parameters from newbie eyes)

So, in the end:

maintenance and evolution of the configuration content is easier
user will see a *common* interface for *all* programs using this project.
user will not see advanced parameters
upgrade of configuration data is easier and sanity check is performed
audit of configuration is possible to check what was modified by the user compated to default values

What about the user interface ?

Config::Model will also come with a Curses::UI interface that queries the user's model and generate the relevant user screens.

What about data storage ?

Since the syntax of configuration files vary wildly form one program to another, most people who want to use this framework will have to provide a dedicated parser/writer.

Nevertheless, this project can also provide a writer/parser for most common format: like ini style file, or provide an interface to the Elektra or debconf projects. This point is open for discussion.

It is entirely possible for a single configuration model to use several parsers and writers so one model will ensure the consistency of several configuration files together.
Last updated on February 27th, 2012

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