rdf2graphml 0.5.0

Converts RDF to GraphML suitable for yEd.

rdf2graphml

Python library for easy converting any RDF to GraphML (http://graphml.graphdrawing.org/specification/xsd.html) compatible with yEd (https://www.yworks.com/products/yed).

Note: This is work in progress!

Usage

rdf2graphml [-h] [-v] [-c CONFIG] [-m MODEL] OUTPUT INPUT [INPUT..] 

Configuration

The RDF-to-GraphML conversion is very customizable. The configuration can be supplied as JSON file and is extracted from a model or ontology. See rdf2graphml.ttl for the configuration ontology.

Example JSON Configuration

{
  "namespaces": {
    "ex": "http://example.org/ontology/"
  },
  "base_dir": "./icons",
  "icon_height": 64,
  "preferred_language": "en",
  "type_as_edge": false,
  "node_properties": [
    "http://www.w3.org/2000/01/rdf-schema#label"
  ],
  "icon_locators": [
    "http://example.org/ontology/iconUrl"
  ],
  "group_type": "http://example.org/ontology/Group",
  "group_contains": "http://example.org/ontology/contains",
  "default_node_style": {
    "blank_nodes": {
      "color": "#DDDDDD",
      "shape": "ellipse"
    },
    "uri_nodes": {
      "color": "#E8EEF7",
      "shape": "roundrectangle"
    }
  },
  "type_styles": {
    "http://example.org/ontology/System": {
      "icon": "system_icon.png",
      "color": "#ADD8E6",
      "shape": "roundrectangle",
      "priority": 10
    }
  },
  "edge_styles": {
    "http://example.org/ontology/dependsOn": {
      "color": "#FF0000",
      "line_type": "dashed",
      "target_arrow": "standard"
    }
  },
  "include_predicates": [
    "*"
  ],
  "exclude_predicates": []
}

Reference

General Settings

• namespaces (object): A dictionary mapping prefixes to namespace URIs. These custom namespaces are registered with the converter to generate shorter QName labels (e.g., ex:Node) for nodes and edges instead of full URIs. Overrides existing prefixes in the source graph.
• base_dir (string): The base directory used to resolve local image paths specified by icon_locators. Defaults to the directory of the configuration file.
• icon_height (integer): The target height in pixels for downloaded/loaded icons. The width is scaled proportionally using Lanczos resampling. Default: 64.
• preferred_language (string): The language tag used to pick the primary rdfs:label for display purposes (e.g., "en" or "de"). If not found, it falls back to a label without a language tag, or an arbitrary one. Default: "de".
• type_as_edge (boolean): If true, rdf:type relations are drawn as explicit edges in the graph. If false, they are collected as node attributes (GraphML Data). Default: false.

RDF Mapping & Extraction

• node_properties (list of strings): A list of URIs. Triples with these predicates are explicitly prevented from becoming edges. Instead, their objects are attached to the subject node as GraphML data attributes.
• icon_locators (list of strings): A list of URIs. If a node has one of these predicates, the converter interprets the object as a URL or local file path to an image, downloads/reads it, converts it to Base64, and renders the node as a yEd ImageNode.

Groups & Hierarchies (Nested Graphs)

• group_type (string): The URI of the rdf:type that identifies a node as a group container.
• group_contains (string): The URI of the predicate used to link a group node to its children. These triples establish the nested graph hierarchy in yEd and will not be drawn as visible edges.

Styling

• default_node_style (object): Fallback styling for nodes.

  • blank_nodes: Style object (color, shape) applied to RDF Blank Nodes. Default: Grey ellipse.
  • uri_nodes: Style object (color, shape) applied to standard URI nodes. Default: Light-blue roundrectangle.

• type_styles (object): Maps rdf:type URIs to specific styles.

  • icon (string): URL or local path to a default image/icon for this type. Takes precedence over shape. If the image fails to load, the converter gracefully falls back to the configured shape.
  • color (string): Hex color code (e.g., "#ADD8E6").
  • shape (string): yEd shape identifier (e.g., "roundrectangle", "ellipse", "hexagon", "diamond").
  • priority (integer): If a node has multiple types, the style with the highest priority wins.

• edge_styles (object): Maps predicate URIs to edge styles.

  • color (string): Hex color code.
  • line_type (string): Supported yEd line types (e.g., "line", "dashed", "dotted").
  • target_arrow (string): Supported yEd arrow types (e.g., "standard", "white_delta", "none").

RDF Lists

The converter automatically aggregates rdf:first/rdf:rest lists into a single node. You can style this generated node by targeting the URI https://www.hedenus.de/rdf2graphml/List.

  "type_styles": {
      "https://www.hedenus.de/rdf2graphml/List": {
          "color": "#FFD700",
          "shape": "hexagon",
          "priority": 100
    }}

Filtering

Filters accept Unix shell-style wildcards (e.g., * or http://example.org/*). The exclusion rules are always evaluated before the inclusion rules.

• include_predicates (list of strings): Only predicates matching these patterns will be drawn as edges. If empty, all predicates (that are not structural/excluded) are allowed.
• exclude_predicates (list of strings): Predicates matching these patterns are completely ignored.
• include_types (list of strings): Only nodes possessing an rdf:type matching these patterns are drawn.
• exclude_types (list of strings): Nodes possessing an rdf:type matching these patterns are explicitly ignored.

Styles known by yEd

shape:

• diamond
• ellipse
• hexagon
• octagon
• parallelogram
• rectangle
• rectangle3d
• roundrectangle
• trapezoid
• trapezoid2
• triangle

line_type:

• dashed
• dashed_dotted
• dotted
• line

target_arrow:

• diamond
• none
• standard
• transparent_circle
• white_delta

Annotating an Ontology

Credits

• User icon (alice.png) created by Heykiyou - Flaticon (https://www.flaticon.com/)
• Battery icon (battery.png) created by Freepik - Flaticon (https://www.flaticon.com/)