Demystifying Graph Modeling: From Nodes & Edges to Rendering Techniques

What is a Graph?

“A graph is a structure consisting of vertices (nodes) and edges (links) that represent relationships between objects.” – Steven S. Skiena

In graph modelling, a node represents an entity and an edge represents a relationship. Nodes are often visualised as dots or circles; edges as lines or curves, optionally directed with arrows.

Basic Graph Model

Node : may contain a textual label, children, parent, depth, degree, and can be visualised as a Dot or Circle .

Edge : connects two nodes, may be a Line or Curve , and can be directed.

Shape : abstract base for visual forms; Dot / Circle are shape specialisations, while Line / Curve are composed of Points .

Geometry Component

To reduce cognitive load, spatial attributes are grouped into a Geometry object that stores distance, size, and relative position. Visual styling such as stroke (width), fill (opacity), and scale belong to a separate Properties object, similar to graph‑database models.

Data Processing and Rendering Pipeline

The workflow consists of two stages:

Parse input text and transform it into a graph data model (nodes, edges, geometry, properties).

Render the model using a 2D drawing engine (e.g., Canvas via Konva.js or SVG).

Layout Strategies

Layout algorithms compute node coordinates before rendering. Common libraries provide ready‑made strategies:

Mermaid – uses dagre.js together with dagre-d3 and D3.

D3.js – offers Force‑Layout, Hierarchy‑Layout, etc.

Cytoscape.js – includes Breadthfirst, Circle, CoSE and extensible plugins.

Emerging AI‑driven layout techniques.

Renderer

Without animation, rendering is a straightforward pass of the computed node positions and visual properties to the chosen medium (Canvas or SVG). Animation introduces additional state handling and is left for future work.

Illustrative Model Diagram

Conclusion

The refined model separates structural concepts (Node, Edge) from spatial (Geometry) and visual (Properties) concerns, facilitating a cleaner and more maintainable graph engine.