<arc>

<arc> encodes an arc, the connection from one node to another in a graph. 19.1 Graphs and Digraphs
Module nets — 19 Graphs, Networks, and Trees
In addition to global attributes In addition to global attributes
from gives 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.
to gives 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.