07_graphml_roundtrip

Example 07 — GraphML round-trip

What it demonstrates

GoGraph's graph interchange I/O: parse a GraphML document into the mutable adjlist builder with graphml.ReadInto, then serialise the same graph back out to two formats — GraphML (graphml.Write) and Graphviz DOT (dot.Write). It shows that a graph survives a read/write round-trip, edges and weights intact.

Domain / scenario

A three-node directed chain with integer edge weights, supplied inline as a GraphML literal:

alice -> bob   (7)
bob   -> carol (9)

The <key> declaration types the weight attribute as long, and the graph's edgedefault is directed, so the DOT export renders as a digraph with label="..." edge weights.

How to run

go run ./examples/07_graphml_roundtrip

Expected output

Ingested 2 edges from GraphML

GraphML out:
<?xml version="1.0" encoding="UTF-8"?>
<graphml xmlns="http://graphml.graphdrawing.org/xmlns">
  <key id="w" for="edge" attr.name="weight" attr.type="long"></key>
  <graph id="G" edgedefault="directed">
    <node id="alice"></node>
    <node id="bob"></node>
    <node id="carol"></node>
    <edge source="alice" target="bob">
      <data key="w">7</data>
    </edge>
    <edge source="bob" target="carol">
      <data key="w">9</data>
    </edge>
  </graph>
</graphml>
DOT out:
digraph G {
  alice -> bob [label="7"];
  bob -> carol [label="9"];
}

The output is byte-for-byte deterministic: both writers iterate nodes in ascending NodeID order, so attribute and edge ordering is stable across runs.

Key APIs

• graph/io/graphml.ReadInto — parse a GraphML document into an adjlist.AdjList[string, int64], returning the edge count.
• graph/io/graphml.Write — serialise an adjacency list back to a GraphML document.
• graph/io/dot.Write — serialise the same graph to Graphviz DOT (digraph for directed graphs, with label="..." weights).

Further reading

• graph/io/graphml — GraphML reader/writer package documentation
• graph/io/dot — Graphviz DOT writer package documentation
• graph/adjlist — the mutable adjacency-list the round-trip loads into
• Example 06 — CSV import — the sibling graph-I/O example
• docs/examples-standard.md — the standard every example follows