Foundations

Required

A Node is the fundamental unit for storing learning materials and data. From Mycel's point of view, learning is simply the manipulation of nodes (creation, updating, scheduling, etc.).

There are a few concepts that should be grasped in order to implement Node in your client.

Fragment vs Spore

Nodes come in two flavors:

Fragment — learning material actively broken down through recursive extractions.
Spore — active learning material reviewed through spaced repetition.

Fragments are dynamic: they are recursively refined and broken down during review sessions until they are atomic enough to become a Spore. Spores are static: once created, they are reviewed over the long term through spaced repetition.

Node vs Learning Unit

Each Node stores shared information, such as resource content, across one or multiple Learning Units. This separation allows multiple Learning Units to share the same content while maintaining independent learning data — for example, to generate multiple Spores from a single piece of text.

A small example

Say you want to learn: Capital of France: Paris, in both directions (capital → country, country → capital).

Using cloze fields, it would be: Capital of {{c1::France}}: {{c2::Paris}}.

The raw content Capital of {{c1::France}}: {{c2::Paris}} is stored in a Spore Node and shared across two Spore Learning Units, each storing separate learning data for its direction.

The capital → country direction could be due in 10 days, whereas country → capital could be due in 1 month. Without the Node / Learning Unit separation, this wouldn't be possible, or would require duplicating the content.

graph LR FragNode["Node base_for: Fragment Always one learning unit"] SporeNode["Node base_for: Spore One / multiple learning units"] FragNode --> FragLU["Learning Unit Fragment (slot 1)"] SporeNode --> SporeLU1["Learning Unit Spore (slot 1)"] SporeNode --> SporeLU2["Learning Unit Spore (slot 2)"] style FragNode fill:#e3f2fd,stroke:#1565c0,stroke-width:2px style SporeNode fill:#e3f2fd,stroke:#1565c0,stroke-width:2px style FragLU fill:#f5f5f5,stroke:#9e9e9e,stroke-width:2px style SporeLU1 fill:#e0f5f0,stroke:#2a9d8f,stroke-width:2px style SporeLU2 fill:#e0f5f0,stroke:#2a9d8f,stroke-width:2px linkStyle default stroke:#90a4ae,stroke-width:1.5px

Why is there a "slot" field?

The slot field distinguishes multiple learning units on the same node. It starts at 1 and goes up to the number of learning units attached.

Handling the distinction

Fortunately, most of this logic is hidden from clients, who work with Node and Learning Units as a single concept.

The API never exposes learning unit IDs directly: you always work with node_id + slot.

How it maps to the API

See the API reference — there are separate "Nodes" and "Learning Units" sections. Learning Unit endpoints exist for convenience and map directly to their Node counterpart. If you want to avoid handling multiple learning units for a single node, simply always pass 1 as slot number — although this is not recommended.

Now let's see how to implement that.