

The question reads like an XY problem, they describe DB functions for data structures so unless there’s some specific reason they can’t use a DB that’s the right answer. A “spreadsheet for data structures” describes a relational database.
But they need rectangular structure. How do they work on tree structures, like OP has asked?
Relationships. You don’t dump all your data in a single table. Take for instance the following sample JSON:
JSON
"users": [
{
"id": 1,
"name": "Alice",
"email": "alice@example.com",
"favorites": {
"games": [
{
"title": "The Witcher 3",
"platforms": [
{
"name": "PC",
"release_year": 2015,
"rating": 9.8
},
{
"name": "PS4",
"release_year": 2015,
"rating": 9.5
}
],
"genres": ["RPG", "Action"]
},
{
"title": "Minecraft",
"platforms": [
{
"name": "PC",
"release_year": 2011,
"rating": 9.2
},
{
"name": "Xbox One",
"release_year": 2014,
"rating": 9.0
}
],
"genres": ["Sandbox", "Survival"]
}
]
}
},
{
"id": 2,
"name": "Bob",
"email": "bob@example.com",
"favorites": {
"games": [
{
"title": "Fortnite",
"platforms": [
{
"name": "PC",
"release_year": 2017,
"rating": 8.6
},
{
"name": "PS5",
"release_year": 2020,
"rating": 8.5
}
],
"genres": ["Battle Royale", "Action"]
},
{
"title": "Rocket League",
"platforms": [
{
"name": "PC",
"release_year": 2015,
"rating": 8.8
},
{
"name": "Switch",
"release_year": 2017,
"rating": 8.9
}
],
"genres": ["Sports", "Action"]
}
]
}
}
]
}
You’d structure that in SQL tables something like this:
Tables
dbo.users
user_id | name | |
---|---|---|
1 | Alice | alice@example.com |
2 | Bob | bob@example.com |
dbo.games
game_id | title | genre |
---|---|---|
1 | The Witcher 3 | RPG |
2 | Minecraft | Sandbox |
3 | Fortnite | Battle Royale |
4 | Rocket League | Sports |
dbo.favorites
user_id | game_id |
---|---|
1 | 1 |
1 | 2 |
2 | 3 |
2 | 4 |
dbo.platforms
platform_id | game_id | name | release_year | rating |
---|---|---|---|---|
1 | 1 | PC | 2015 | 9.8 |
2 | 1 | PS4 | 2015 | 9.5 |
3 | 2 | PC | 2011 | 9.2 |
4 | 2 | Xbox One | 2014 | 9.0 |
5 | 3 | PC | 2017 | 8.6 |
6 | 3 | PS5 | 2020 | 8.5 |
7 | 4 | PC | 2015 | 8.8 |
8 | 4 | Switch | 2017 | 8.9 |
The dbo.favorites table handles the many-to-many relationship between users and games; users can have as many favourite games as they want, and multiple users can have the same favourite game. The dbo.platforms handles one-to-many relationships; each record in this table represents a single release, but each game can have multiple releases on different platforms.
I think you’re misrepresenting that a little. It’s not peer reviewed, doesn’t appear to have any researchers names attached at all, doesn’t mention latent demand, and doesn’t at any point consider that there could be other modes of transport. It reads to me like someone trying to sell their road building project.