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# Conditions Overview

Conditions are the core of Reactor's programmable logic. It's hard to imagine a useful rule that doesn't have at least one condition. A condition is a logic test that Reactor will perform, so in order to make Reactor do something, you have to have at least one condition to test something.

Important Concept!

Conditions are boolean, and so have only two states: true and false. Once a condition becomes true, it remains true until the underlying test(s) fail, at which point it becomes false.

Conditions are organized into one or more condition groups. All rules contain a group called the root group, and it is the group that contains all other groups and conditions. The state of the rule overall (its tripped state) is also determined by the state of the root group. When the root group is true, the rule will be tripped; it is untripped otherwise.

You may create as many condition groups as you need. Groups can be nested--you can create groups within groups. This allows very complex logic conditions to be created. When writing a logic operation out, such as `( (A OR B OR C) AND (D OR E) AND NOT F )`, the parenthetical expressions are equivalent to condition groups in Reactor, so in structuring your configuration, it may be helpful to write out your logic in this way before launching into the Conditions editor.

Important Concept!

When logic is written out as in the example above, the expressions in parentheses are equivalent to condition groups in Reactor.

Each condition group has an associated logic operation, and the state of the group is the result of that operation performed on the results of the conditions within it:

- `AND` - All conditions in the group must be true for the group state to be true;
- `OR` - Any condition (one or more) in the group must be true for the group state to be true; the group is only false when all of its conditions are false;
- `XOR` - Exactly one of the conditions in the group must be true for the group state to be true; if none or more than one are true, the group state is false;
- `NOT` - Invert the result of AND/OR/XOR;
- `NUL` - The group state is null, which means it does not make a contribution to the logic state of its parent group; logic elements within the NUL group still evaluate and generate results, however, so subgroups of a NUL group can have Activities.

Important Concept!

Since a group is a kind of condition that contains other conditions, it therefore applies that a group, like any condition, can only be true or false. It cannot be more true or more false. If an OR group, for example, contains two conditions, and one of them becomes true, then group becomes true. If the second condition in the group later becomes true, the group state does not change — it's already true and it cannot become "more true." This is very important to understand when it comes to running Activities, discussed later.

In addition to each condition's specific test operation, most condition types have condition options that can be used to further modify their evaluation state, or restrict when the condition is true (for example, only after the test condition has been met for a period of time, or a number of times within a period of time, or in sequence following another condition). See Condition Options for full details.

## Creating and Organizing Groups and Conditions

To create a group, one simply clicks on the "New Group" icon at the bottom of the root group or another existing group. The new group will be created as a child of that group. When you create a new group, it will be given a default name that is the same as its group ID. These aren't very readable or descriptive for humans, so you should change it by clicking on the name in the group's header and entering a new name. Click outside the input field to save the new group name. You can change the group name at any time--it is only used for display.

To add conditions to a group, click the "New Condition" icon at the bottom of the group. Then select its type and options.

The nesting and ordering of conditions can be changed by drag-and-drop. The "hamburger" icon in the tools area of the condition group (its upper-right corner) can be grabbed and the entire group moved to another position in the hierarchy. Individual conditions can be moved and reorganized in a similar manner.

Groups can be disabled by clicking the "Disable" button in the group header. Disabling a group has the effect of stopping the evaluation of all conditions in the group (including nested child groups). A disabled group does not contribute to the logical result of its parent (it's treated as if it does not exist).

## Condition Types

A group may thus contain other groups, or conditions. Conditions are the fundamental building blocks of the logic--the tests that can be performed on device or system states.

There are currently eight different condition types:

- Entity - Test the various attributes of entities (e.g. light on/off, volume level, motion detected);
- Rule - Test the state of another rule;
- Date/Time - Test the current date and time;
- Sunrise/Sunset - Test the current time against dawn and disk;
- Day of Week - Test the current day;
- Expression Value - Tests the value of an expression variable;
- Interval - Trigger at a fixed, recurring interval;
- Restart - Respond to Reactor restarting/the system rebooting;
- Comment - Just text to help you remember what you did.

## Edge-driven Actions

Reactor's condition results and state changes are edge-driven, which is to say, changes in state cause action, not the states themselves. So, when a condition or group transitions from false to true, that may cause an action, but the object remaining in true state thereafter does not cause those actions to re-run continuously.

On individual conditions, this means that if a condition is true as a result of its operation, it is not "more true" if the underlying value changes and still results in a true evaluation result. For example, if the test expression is "CurrentTemperature >= 50", and the sensor reports 49 first, and then 50, the Reactor condition will change from false to true and Reactor marks the time of the change at that moment. If the sensor then later reports 51, the condition test is still true, but that is not a change in condition state, so the condition time is not modified.

At a group level, Reactor handles the group states the same as individual condition states: the change marks time, but a subsequent evaluation yielding the same result (no change) does not modify the time. Groups are, in fact, just handled as a special type of condition within Reactor.

Reactor itself, then, behaves similarly to conditions and groups. Once tripped by the root group becoming true, a change in the conditions or groups underlying the root group that still results in a true result leaves the rule tripped, and it does not retrigger any activities or scene triggers/watches that may be associated with it (at least, not by default).

Tip

Keep this simple rule in mind when creating your logic: group activities and triggers are only fired when there is a change in logical state from true to false or false to true.

## Simplifying Your Logic

You'll find your logic can get quite complex pretty quickly, especially when you start adding details and tweaks. You'll often find you even need to completely restructure your logic, as the addition of one more element is a straw that breaks the proverbial camel's back and either makes your logic too complex to understand, or is simply structured in a way that prevents you from easily adding the new conditions to handle the case. To simplify a complex rule, consider breaking it up into several rules.

Updated: 2023-Apr-17