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The RDF Graph Modeling Language (RGML) is a W3C RDF vocabulary to describe graph structures. General graphs can be seen as Web resources. RGML defines graph, node, and edge as RDF classes and attributes of graphs, such as label and weight, as RDF properties. Some of these RDF properties establish relationships between graph, node, and edge instances. Hence, a graph instance "knows" which node and edge instances belong to this graph. RGML can be easily combined with other RDF vocabularies to add new properties, for example, you can add a Dublin Core "dc:title" property to a node instance to assign a string title to a node. Using RGML we can also define web collections (a collection of web pages that represent one document) as subgraphs of a graph (webgraph).
For more information, browse the following RGML resources: