Story: Home Security

[Yoric]

Meta-bug: #2

When I am on vacation, if my bedroom door opens, I want to receive a
picture of whatever happened in my bedroom.

Can be expressed as

I need:
- a `door opening detector` with property `door is opened`;
- a `camera` with property `image`;
- a `communication channel to user` to `send text message` and `send image`.

1. When `door is opened` of `door opening detector` switches to true
    do `send text message` with `communication channel with user`:
       "Someone entered your bedroom"
    do `send image` with `communication channel with user`:
      `image` of `camera`.

Input devices

• door opening detector, with property door is opened;
• camera, with property image

The camera is a weird case, since property image can typically weigh several Mb.

Output devices

• communication channel with user with capability send image

Values

• The image is most likely a blob (binary data + mime type). The
  rules engine doesn't know what to do with it.
• Regardless of how many times we access the value image of camera
  during the evaluation of the trigger, this value is cached.
• Behind-the-scenes, requesting the image of camera is async. The
  interpreter hides this from the user.

Blocked by

• Issue Support sending non-constant data to effectors #23 Support sending non-constant data to effectors