> ## Documentation Index
> Fetch the complete documentation index at: https://docs.learningcommons.org/llms.txt
> Use this file to discover all available pages before exploring further.

# Core concepts

> Learn the fundamental concepts of Knowledge Graph including how they are composed of nodes and relationships.

## Datasets

Knowledge Graph organizes educational information into 4 categories of datasets: Curriculum, Academic Standards, Learning Progressions, and Learning Components.

These datasets are modeled as graphs, using [entities](#entities) (the elements in the dataset) and [relationships](#relationships) (the way these elements are connected).

## Entities

Each entity (or node) represents a distinct concept in the domain, such as an academic standard or learning component. These entities define the core elements of the dataset.

## Relationships

Each relationship (or edge) represents a directed connection between two entities (or nodes). These relationships define how entities relate to one another within the graph.

Relationships are expressed as a triple:

* Source entity's UUID
* Relationship UUID
* Target entity's UUID

## UUID

Every entity and relationship carries a UUID – these UUIDs link entities together in relationships. Conceptually, this is similar to how foreign keys are used to `JOIN` tables in a relational database.

UUIDs make it easy to deterministically join files, reference entities, and preserve links across datasets. It makes connections explicit without relying on schema-level constraints and avoids tight coupling to any one database system. Some UUIDs come from external sources such as the [CASE Network](https://casenetwork.1edtech.org/) ↗, which ensures interoperability.