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Graph description syntax

Write nodes and edges as text. Add labels, types, or classes when you need them. Use layout requirements to say where graph elements belong.

Names. Edge labels, types, and classes can contain letters, digits, and underscores, and must start with a letter. Edge labels, types, and classes must have distinct names and cannot contain spaces and hyphens.

Edges

Write one edge per line. Reuse an ID to connect edges to the same node:

A -> B
B -> C

A label after : names a relationship. A layout requirement can target every edge with that label (see Selectors):

A -> B : hit
A -> C : miss

@orientation(selector=hit,  directions=[right])
@orientation(selector=miss, directions=[below])

Nodes, labels, and IDs

Write id[Display label] when the visible label should differ from the ID used by edges:

cs2[CS 2] -> algorithms[Algorithms and Data Structures]
cs2 -> systems[Systems]
Display labels can

Types

Add :::Type to assign a type to a set of nodes. 

algorithms[Algorithms]:::Course -> fall[Fall term]:::Term
systems[Systems]:::Course      -> fall

@atomStyle(selector=Course, borderStyle(color='#795db4', width=2))
@atomStyle(selector=Term, borderStyle(color='#b85c38', width=2))

univ selects every node, including those without an explicitly declared type. A node can only have one type.

Comments

%% starts a line comment. Write requirements as bare @name(...) lines; %%@name(...) is a comment and does not apply a rule.

Mermaid compatibility

These Mermaid flowchart forms parse, with the changes shown below. Unsupported diagram types and subgraphs stop compilation rather than showing a partial or misleading diagram. Other lost appearance or behavior is reported as a warning on the source line.

Mermaid form read as
leading graph TD / flowchart LR ignored (no layout direction here)
A --> B an edge
A -.-> B, A ==> B, A --- B an edge, with a warning that dotted, thick, or open-link styling was lost
A -->\|left\| B a labeled edge, label left
A -- left --> B a labeled edge, label left
cs[Algorithms] a node with display label Algorithms
cs(Algorithms), cs{Algorithms}, cs((Algorithms)) a node with display label Algorithms, with a warning that its shape was lost
classDef …, style …, linkStyle …, click … ignored with a warning
subgraph … end error; subgraphs are not supported
non-flowchart headers such as sequenceDiagram, gantt, or pie error; the diagram is not rendered

For edge and node styling, use style directives.

Machine-readable reference

The language manifest lists authoring forms, requirement arguments, style blocks, and allowed values. It links to the upstream selector manifest. The same file is exported as spytial-gdl/language.json. Run npm run manifest to regenerate it; npm test checks that it is current.

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