Density.md
# Density
The goal is to talk about density of information in data format like `XML`, `JSON`, `YAML`, `HTML`, `CSV`
## Node Density
The node density is the number of node that we can create with any given amount of bytes
### XML Node Density: max 40%
For example, the maximum node density is reached via this simple pattern
```xml
a<b/>
```
which makes 5 bytes long and generates 2 nodes:
* a `text node` with the string "a"
* a `element` with the name "b"
So in the end
```xml
<r>(a<b/>)+</r>
```
is the densiest `XML` available in node density: 40%.
### JSON Node Density: max 50%
For example, the maximum node density is reached via this pattern
```json
[1,1, ... ,1]
```
which provides 1 node (number_value) for each 2 bytes: "," and "1".
So in the end
```json
{"A":[1,1, ... ,1]}
```
is the densiest `JSON` available in node density: 50%.
## Event Density
The event density is the number of event that we can create with any given amount of bytes. Their is a direct relationship with Node density:
* Node density <= Event density (always)
It comes from the fact that every node that is always a leaf (attribute, processing-instruction) generates 1 events, while node that can contains other node always generate 2 events (`start_element`, `end_element`)
### XML Event Density: max 60%
For example, the maximum event density is reached via this simple pattern
```xml
a<b/>
```
which makes 5 bytes long and generates 3 events:
* a `text event` with the string "a"
* a `start_element` event with the name "b"
* a `end_element` event with the name "b"
So in the end
```xml
<r>(a<b/>)+</r>
```
is the densiest XML available in event density: 60%
### JSON Event Density: max 99,99%
#### Zero depth: max 66,67%
For example, the maximum node density is reached via this pattern
```
[{},{}, ... ,{}]
```
which provides 2 events (`start_object` and `end_object`) for each 3 bytes: "," and "{" and "}".
So in the end
```json
{"A":[{},{}, ... ,{}]}
```
is the densiest JSON available in Event density without depth: 66,67%.
#### Increasing depth: max 99,99%
For example, the maximum node density is reached via this pattern
```json
[[[.....[[......]].....]]]
```
which provides 2 events (`start_array` and `end_array`) for each 2 bytes: "[" and "]".
So in the end
```json
{"A":[[[.....[[......]].....]]]}
```
is the densiest JSON available in Event density with depth: 99,99%.