Getting started

Installation

• Open a shell session

Optional: install the Rougail library in a virtual environment

• install the virtual environment: python -m"venv' .venv

• activate it ./.venv/bin/activate (or .venvScriptsactivate.exe under windows)

Rougail’s library installation

You can use the pip python installer, here is the install command:

pip install rougail

What is a consistency handling system ?

Rougail, Tiramisu: What is it all about?

Question: OK, I have understood that the Rougail library allows me to take advantage of the Tiramisu consistency handling library. But what is all this for? What is exactly a consistency handling system? And again, what is this Tiramisu library used for?

Answer: Well, we will explain in details what this Tiramisu library is and what Rougail is.

In (very) short:

• Rougail is the YAML consistency description of a context‘s situation

• Tiramisu is the consistency engine linter

Tiramisu

Tiramisu is a consistency handling system that has initially been designed in the configuration management scope. Until now, this library is generally used to handle configuration options.

It manages variables and group of variables. In the Tiramisu scope we call it options and option descriptions.

Here is the tiramisu documentation.

In the Rougail scope, we call it variables and families. In Rougail, the families and variables are located in the structure files.

The structure files

structure file

A structure file in the Rougail meaning is a YAML file that describes variables and their dependencies. There can be a lot of structure files located in many different folders.

Rougail reads all the structure files and loads them into a single object that represents the whole context.

The Rougail process from structure files to Tiramisu object

structured data

We sometimes call ‘structured datas’ the datas that are in the structure files, as opposed to user datas. For example when a value of a variable is defined in the structured datas, that is in a structured file, the assigned value’s status is that the variable’s value is a default value. If the assigned value of the variable is defined in a user data file, it is an user assigned value.

We’ll see later on some examples of default values and user assigned values.

The main advantage of all of this that declaring variables and writing consistency is as simple as writing YAML. With Rougail it is not necessary to write Tiramisu code any more. It simplifies a lot of things.

And rather than writing Tiramisu code, we can declare variables and describe the relationships between variables in a declarative style (that is, in a YAML file).

Once the structure files are loaded by Rougail, the Tiramisu configuration management tool can check the consistency of the variables between them.

The variables

Here is a structure file example with only a variable variable named proxy_mode A variable can be defined with no default value at all.

A Rougail dictionnary file with a variable named proxy_mode, with a description.

---
proxy_mode:
  description: Configure Proxy Access to the Internet

The same with a default value:

A Rougail dictionnary file with a variable named proxy_mode, with a default value.

---
proxy_mode:
  description: Configure Proxy Access to the Internet
  default: No proxy

variable

A variable is a declaration unit that represents a business domain metaphor, the most common example is that a variable that represents a configuration option in a application, but a variable represents something more that a configuration option. It provides a business domain specific representation unit.

Families of variables

family

A family is simply a container of variables and/ore some subfamilies.

Here how a YAML structure file with a family looks like:

A hello.yml structure sample file

 ---
 version: '1.1'
 world:
   description: Hello world family container
   name:
     description: Somebody to say hello
     default: rougail

Here, we have a family named world. This family contains a variable named name