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Perl module to create configuration editor wtih semantic validation
Perl Perl6

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Config::Model - Describe and edit configuration data

Config::Model enables a project developer to provide an interactive
configuration editor (graphical, curses based or plain terminal) to
his users. For this he must:
- describe the structure and constraints of his project's configuration
- find a way to read and write configuration data. This can be provided 
  by Config::Model backends or by custom code

With the elements above, Config::Model will generate interactive
configuration editors (with integrated help and data validation).
These editors can be graphical (with Config::Model::TkUI), curses
based (with Config::Model::CursesUI) or based on ReadLine.

How does this work ?

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

   1. The user interface (config-edit program and some other optional modules)
   2. The validation engine which is in charge of validating all the
      configuration information provided by the user. This engine is
      made of the framework provided by this module and the
      configuration description (often refered as "configuration model").
   3. The storage facility that store the configuration information
      (currently several backends are provided: ini files, perl files,
      and Augeas)

The important part is the configuration model used by the validation
engine. This model can be created or modified with a graphical editor
(provided by Config::Model::Iself).

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 ?

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

A configuration model can be created and modified with the graphical
interface provide by Config::Model::Itself. The model is saved in a
declarative form (currently, a Perl data structure). Such a model is
easier to maintain than a lot of code.

The model 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 (beginer, advanced, master)
- on-line help (for each parameter or value of parameter)

So, in the end:
- maintenance and evolution of the configuration content is easier
- user will see a *common* interface for *all* programs using this
- beginners will not see advanced parameters (advanved and master
  parameters are hidden from beginners)
- upgrade of configuration data is easier and sanity check is
- audit of configuration is possible to check what was modified by the
  user compared to default values

What about the user interface ?

Config::Model interface can be:
- a shell-like interface (plain or based on Term::ReadLine).
- Graphical with Config::Model::TkUI (Perl/Tk interface).
- based on curses with Config::Model::CursesUI. This interface can be
  handy if your X server is down.

All these interfaces are generated from the configuration model.

And configuration model can be created or modified with a graphical
user interface (with Config::Model::Itself)

What about configuration 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 provides a writer/parser for some common
format: ini style file and perl file. With the additional
Config::Model::Backend::Augeas, Augeas library can be used to read and
write some configuration files. See for more

Is there an example of a configuration model ?

The "example" directory contains a configuration model example for the
/etc/fstab file. This example includes a small program that use this
model to show some ways to extract configuration informations.

If you want to discuss Config::Model ?

Subscribe to the config-model-users list:

or to the development list:

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