Add Rules Concepts page

rules/concepts.md

@@ -1,25 +1,53 @@
-# Cover generic rules concepts
+# Rules Concepts
 
-Pull stuff from the Getting Started Tutorial.
+openHAB is about home automation, but to create home automation we need to define rules.
+
+{::options toc_levels="2..4"/}
+
+- TOC
+{:toc}
 
 ## What Are Rules
 
+You can think of rules as routines or behaviours for your smart home.
+
+Many people have a routine when they wake up in the morning: make the bed, make coffee, make and eat breakfast, brush their teeth, etc.
+Similarly your smart home can have a routine: when the sun rises raise the blinds and adjust the temperature.
+Another routine could be to turn off all the lights and turn down the temperature when you leave home:
+openHAB can do that for you.
+There is no need to open your app and switch of the lights manually.
+Do you want to hear your favorite music when you arrive back at home?
+No problem, openHAB can do that for you too.
+Rules can also remind you of things, for example, that you opened the window hours ago and forgot that it is open?
+openHAB can send a notification to your phone.
+
 ## Parts of a Rule
 
-### Triggers
+These rules take the high level form of *When __t__ happens, if __c__ then do __a__*,
+where __t__ are the _triggers_ that cause the rule run,
+__c__ are the _conditions_ that must be true for the rule to run, and __a__ are _actions_ to perform when the rule is triggered and allowed to run.
+Note that both __t__ and __c__ can be optional.
+
+To work with the *When __t__ happens, if __c__ then do __a__* principle, openHAB rules consist of three parts:
+
+| Name        | Rule Part            | Purpose                                                  |
+|-------------|----------------------|----------------------------------------------------------|
+| `Trigger`   | *When __t__ happens* | Causes the rule run when the defined event happens.      |
+| `Condition` | *if __c__*           | Which condition has to be met that the rule really runs? |
+| `Action`    | *then do __a__*      | What should be done when the rule runs?                  |
 
-### Conditions
+Any single rule is not required to have all of these (although a rule without an action is not very sensible).
+An individual rule can also have more than one of each.
 
-### Script Actions
+A rule that should always run when triggered will have zero conditions.
+An individual rule can respond to several different triggers by having multiple different triggers set up.
 
-### Available Values
+Even though it might not seem sensible first, as the rule would never run on it's own, one can also have a rule with no triggers.
+But why would somebody want such a rule?
+In some cases, it is useful to have a rule that is only manually triggered.
+Sometimes there is advantage in a rule that calls another rule.
+In both cases, the rule has no triggers and no conditions.
 
-formerly implicit variables
 
-### Helper Libraries
 
-### Templates
-How to find and install.
-How to write will be on a later page.
 
-### Comprehensive Examples