Data Format

ArrowCrab reads a JSON object matching GraphData. The wire format contains flat-packed numeric records and one shared string table.

Top-level object

interface GraphData {
  subgraphs: number[];
  nodes:     number[];
  edges:     number[];
  strings:   string[];
}

Each packed array must have a length divisible by its record width. An empty strings[] is valid when no node records reference it; every node label and color otherwise requires a valid string-table index.

Node records

Every three consecutive values in nodes[] form one record.

Offset	Field	Meaning
`i + 0`	`id`	Safe-integer node ID
`i + 1`	`label`	Integer index into `strings[]`
`i + 2`	`color`	Integer index into `strings[]`; interpreted as a CSS color by the renderer

Edge records

Every four consecutive values in edges[] form one record.

Offset	Field	Meaning
`i + 0`	`sourceId`	Source node ID
`i + 1`	`sourcePort`	Non-negative source output-port index below `4,294,967,295`
`i + 2`	`targetId`	Target node ID
`i + 3`	`targetPort`	Non-negative target input-port index below `4,294,967,295`

Subgraph records

Every three consecutive values in subgraphs[] form one record.

Offset	Field	Meaning
`i + 0`	`nodeId`	Compound node that owns the scope
`i + 1`	`inId`	Scope entry boundary node
`i + 2`	`outId`	Scope exit boundary node

Validation rules

The validator applies these rules before constructing the resolved model:

All ID and port fields are safe integers; label and color references are integer indexes.
Node records may appear in any order. Node IDs must be unique.
Each edge references existing nodes and satisfies sourceId < targetId.
Each subgraph has three existing IDs, satisfies inId < outId, and places nodeId outside the closed interval [inId, outId].
Two subgraph records may not reuse the same (inId, outId) pair.
Every label and color reference is an integer index inside strings[], and every string-table entry is a string.
Port indexes are non-negative and less than 4,294,967,295.

The increasing-ID and edge-direction rules establish the topological order used by the viewer. The wire format carries scope boundaries rather than an explicit child list; scope membership is resolved from those intervals.

Scope semantics

A node belongs to the innermost scope whose open interval strictly contains its ID: inId < nodeId < outId. Entry and exit boundary nodes are excluded from a scope's nodeIds, and the compound owner is outside the closed interval. Boundary ports still contribute to the compound frame's port counts.

An edge belongs to the innermost scope for which both endpoints are inside, or one endpoint is inside and the other is that scope's boundary.

Port-count inference

Port counts are not stored in the wire format. For each node, the input count is the maximum referenced targetPort + 1, and the output count is the maximum referenced sourcePort + 1. The same inference is used for entry and exit boundary nodes when the renderer draws ports on a compound frame.