content: usage: advanced: cover data-lake

Author: ES-Alexander

content/usage/advanced/data-lake-compound-variable.png

@@ -527,6 +527,9 @@ the cause of the problem:
 
 {{ easy_image(src="video-widget-stats", width=170, center=true) }}
 
+These statistics are also available through the [data-lake](#data-lake), and can be [plotted](#data-plotting)
+for monitoring/analysis outside of the video widget if desired.
+
 ##### WebRTC Video Recorder
 It is possible to directly record an incoming WebRTC video stream (not the scaled and cropped/flipped/rotated
 display of the widget):
@@ -651,27 +654,20 @@ self-replacing mjpeg like from an ESP32-Cam. It could also display images hosted
 The plotter widget allows plotting data on a graph:
 {{ easy_image(src="plotter-widget", width=300, center=true) }}
 
-Configuration options are provided for selecting the variables to plot, and modifying basic appearance
-characteristics:
+Configuration options are provided for selecting the [data-lake variable](#data-lake) to plot, and 
+modifying basic appearance characteristics:
 {{ easy_image(src="plotter-config", width=450, center=true) }}
 
 It is possible to change the decimal resolution of the displayed statistics, and the limit the number
 of plotted samples to improve visibility and performance.
 
-{% note() %}
-The data lake which the widget gets its data from by default provides access to the Cockpit memory
-usage, MAVLink message fields, and values added from [Custom Actions](#custom-actions). It will soon be 
-connected to the BlueOS-specific options available to
-[Very Generic Indicators](#very-generic-indicators) as well.
-{% end %}
-
 #### Do It Yourself Widget
 
 - Completely custom elements, code logic, and styling
 {{ easy_image(src="diy-widget-config", width=550, center=true) }}
 - Runs code automatically when Cockpit starts/refreshes
-- Can listen to, create, and modify data lake variables, and register and/or execute Actions using the
-  Cockpit API (`window.cockpit.*`)
+- Can listen to, create, and modify [data-lake variables](#data-lake), and register and/or execute Actions
+using the Cockpit API (`window.cockpit.*`)
 - Can be exported to or imported from a JSON file with `"html"`, `"css"`, and `"js"` string fields
 
 #### Container Widgets
@@ -761,6 +757,17 @@ as the router](https://blueos.cloud/docs/latest/usage/advanced/#mavlink-endpoint
 interface provided.
 {% end %}
 
+### Data Lake
+
+- Internal data management and storage system
+- Includes information about Cockpit, the vehicle, video streams, MAVLink telemetry, and widget and Action internals
+{{ easy_image(src="data-lake-overview", width=600, center=true) }}
+- Supports defining custom variables:
+   - These can be [set using joystick buttons](#data-lake-variables)
+{{ easy_image(src="data-lake-custom-variable", width=450, center=true) }}
+- Allows defining compound variables, which are computations based on and/or combining other variables:
+{{ easy_image(src="data-lake-compound-variable", width=450, center=true) }}
+
 ## Behaviour Configuration
 
 Cockpit's behaviour can be configured via the [sidebar menu](#sidebar-menu), with the following tabs:
@@ -881,6 +888,11 @@ Joystick buttons can also be configured to run more general functionalities, lik
 sending a single MAVLink message. These options can be provided (or defined) using
 [Cockpit's Action system](#cockpit-actions-1).
 
+##### Data Lake Variables
+
+When it is useful for the button state to represent a value within some other functionality, the button can
+be configured to control a variable within Cockpit's [data-lake system](#data-lake).
+
 ##### Modifier Keys
 
 Modifiers allow sacrificing one button in order to add an extra functionality slot for every non-modifier button.