rdf2graphml 0.10.1

Converts RDF to other graph formats like GraphML (yEd), drawio or Cytoscape.js

rdf2graphml

Python library for easy converting any RDF to other formats, like GraphML compatible with yEd or drawio.

The RDF-to-GraphML conversion is very customizable. The basic idea is to extend an existing model or ontology with visualization properties. The ontology for these annotation properties is found here: rdf2graphml.ttl.

If you do not have a model or ontology you can specify a JSON configuration file.

Usage

[-h] [-V] [-v] [--base_dir BASE_DIR] [--type_as_edge] [-m MODEL] [-c CONFIG] -o OUTPUT [inputs ...]

If you use -m and -c option, the JSON configuration will be loaded first. The model properties will then overwrite the JSON configuration. In any case the command line option --type_as_edge takes precedence.

The converter automatically detects the format of your inputs files based on their file extensions. The following formats are supported out of the box:

Standard RDF Formats: Any format supported by rdflib and explicit support for .jsonld.

Graffl: Native support for parsing .graffl files - see the graffl project.

Configuration

While the annotation properties in the provided RDF ontology use camelCase (e.g. rdf2graphml:lineWidth), the corresponding keys in the JSON configuration use snake_case (e.g. line_width). Your actual RDF URIs used in the configuration remain unchanged.

Annotating a Model or Ontology

Annotating a model or ontology is simple, just add the layout properties to your types:

@prefix rdf2graphml: <https://www.hedenus.de/rdf2graphml/> .

<http://example.org#System> a owl:Class ;
  rdf2graphml:icon "icons/my_icon.png" .

<http://example.org#note> a rdf:Property ;
  rdf2graphml:color "#FFAAAA" ;
  rdf2graphml:lineWidth "2.0" .

Example JSON Configuration

{
  "namespaces": {
    "ex": "http://example.org/ontology/",
    "schema": "http://schema.org/",
    "rdf2": "https://www.hedenus.de/rdf2graphml/"
  },
  "icon_height": 80,
  "preferred_language": "de",
  "type_as_edge": false,
  "node_properties": [
    "http://www.w3.org/2000/01/rdf-schema#comment",
    "http://example.org/ontology/internalId"
  ],
  "icon_locators": [
    "http://example.org/ontology/hasIcon",
    "https://www.hedenus.de/rdf2graphml/icon"
  ],
  "group_type": "http://example.org/ontology/SystemBoundary",
  "group_contains": "http://example.org/ontology/containsComponent",
  "default_node_style": {
    "blank_nodes": {
      "color": "#F0F0F0",
      "shape": "ellipse"
    },
    "uri_nodes": {
      "color": "#DAE8FC",
      "shape": "roundrectangle"
    }
  },
  "type_styles": {
    "http://example.org/ontology/Database": {
      "icon": "database_icon.png",
      "color": "#FFE6CC",
      "shape": "cylinder",
      "priority": 20
    },
    "http://example.org/ontology/Service": {
      "color": "#D5E8D4",
      "shape": "rectangle",
      "priority": 10
    },
    "https://www.hedenus.de/rdf2graphml/List": {
      "color": "#FFFF88",
      "shape": "hexagon",
      "priority": 100
    }
  },
  "edge_styles": {
    "http://example.org/ontology/calls": {
      "color": "#0000FF",
      "line_type": "line",
      "line_width": "2.0",
      "target_arrow": "standard",
      "label": "ruft auf"
    },
    "http://www.w3.org/1999/02/22-rdf-syntax-ns#type": {
      "color": "#888888",
      "line_type": "dashed",
      "target_arrow": "transparent_circle"
    }
  },
  "include_predicates": [
    "http://example.org/*",
    "http://www.w3.org/1999/02/22-rdf-syntax-ns#type"
  ],
  "exclude_predicates": [
    "http://example.org/ontology/ignoredProperty"
  ],
  "include_types": [
    "*"
  ],
  "exclude_types": [
    "http://example.org/ontology/HiddenType"
  ]
}

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.
• 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: "en".
• 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 and embeds it.

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 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): Shape identifier
  • 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 (e.g. "#ADD8E6").
  • line_type (string): Line type identifier.
  • line_width (string): Line width (e.g. 2.0).
  • target_arrow (string): Arrow types identifier.

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
    }}

Links

If you want to create clickable hyperlink you can use the type rdf2graphml:Link. If a node is hyperlink then the label text will be underlined. If the node is a blank node, then the url property is taken from rdf:value.

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

Also see the application's documentation.

shape:

• diamond
• ellipse
• fatarrow (pointing to right)
• fatarrow2 (pointing to left)
• hexagon
• octagon
• parallelogram (skewed right)
• parallelogram2 (skewed left)
• rectangle3d
• rectangle
• roundrectangle
• star5
• star6
• star8
• trapezoid (pointing up)
• trapezoid2 (pointing down)
• triangle (pointing up)
• triangle2 (pointing down)

line_type:

• dashed
• dashed_dotted
• dotted
• line

target_arrow:

• circle
• delta
• diamond
• none
• plain
• short
• standard
• transparent_circle
• white_circle
• white_delta
• white_diamond

Credits

• User icon (alice.png) created by Heykiyou - Flaticon
• Battery icon (battery.png) created by Freepik - Flaticon
• User icon (user.png) created by meaicon - Flaticon