Improve format of configurations

[ikedas]

Expected Behavior

The format of the configuration file(s) should be as uniform, flexible, and generic as possible.

Current Behavior

• Each part of the configuration is divided into various configuration files, data source definitions, XML file for list creation, dump files and so on.
• Each of the configuration uses a (generally different) hand-made format on an ad hoc basis. (For example, common parameters are written in different formats for individual list settings and for domain or site-wide settings.) Hand-made formats increase the cost of maintenance.
• Sometimes the format is not expressive enough to describe the settings. Example: scenario files, task files.

Possible Solution

I propose that we move to a format that is as uniform and generic as possible.

Here are some candidates along with their pros / cons:

\	JSON	Lua	TOML	UCL	YAML	Comments
Human-easily-readable	Less	Less	More	More	More
Strict grammer	Strict	Strict	Strict	Tolerant	Tolerant	Whether a partial error invalidates the whole or not.
Comment syntax	No	Yes	Yes	Yes	Yes	Grammatical elements for notes that do not make sense as data.
Inclusion syntax	No	Yes	No	Yes	No	Grammatical elements to include data fragments from other files.
Scripting capability	No	Yes	No	No	No	Runtime control including conditional branching.
(Upper-)compatible to JSON	-	No	No	Yes	Yes(*)	(*) YAML: Some implementations, e.g. YAML-Tiny, are not compatible.
Unity of specification in actual implementations	High	High	High	High	A bit diverse
Implementations for Perl	JSON, JSON-XS	Lua-API	TOML-Tiny, TOML-XS	Config-UCL	YAML, YAML-PP, YAML-PP-LibYAML, YAML-Safe, YAML-Syck, YAML-Tiny, YAML-LibYAML

Lua is not a configuration file in the usual sense, but it would be useful for migrating scenarios and tasks definitions. For the other configuration files, we could choose from the remaining four.

Planned tasks

TBD.

Related issues

• #17
• #1157