<arc>

<arc> encodes an arc, the connection from one node to another in a graph. 19.1 Graphs and Digraphs
Modulenets — 19 Graphs, Networks, and Trees
AttributesIn addition to global attributes
fromgives the identifier of the node which is adjacent from this arc.
Status Required
Datatype 

<rng:ref name="data.pointer"/>
data.pointer
Values The identifier of a node.
togives the identifier of the node which is adjacent to this arc.
Status Required
Datatype 

<rng:ref name="data.pointer"/>
data.pointer
Values The identifier of a node.
Used by
graph
May contain
core: label
Declaration

<rng:element name="arc">
<rng:ref name="att.global.attributes"/>
<rng:attribute name="from">
 <rng:ref name="data.pointer"/>
</rng:attribute>
<rng:attribute name="to">
 <rng:ref name="data.pointer"/>
</rng:attribute>
<rng:optional>
 <rng:ref name="label"/>
 <rng:optional>
  <rng:ref name="label"/>
 </rng:optional>
</rng:optional>
</rng:element>
element arc
{
   att.global.attributes,
   attribute from { data.pointer },
   attribute to { data.pointer },
   ( label, label? )?
}
Example
<arc from="#T3" to="#T3">
 <label>OLD</label>
 <label>VIEUX</label>
</arc>
Note
The arc element must be used if the arcs are labeled. Otherwise, arcs can be encoded using the adj, adjTo and adjFrom attributes on the node tags in the graph. Both arc tags and adjacency attributes can be used, but the resulting encoding would be highly redundant.
Zero, one, or two children label elements may be present. The first occurence of label provides a label for the arc; the second provides a second label for the arc, and should be used if a transducer is being encoded.