<arc>

<arc> encodes an arc, the connection from one node to another in a graph. 19.1 Graphs and Digraphs
組件nets — 19 Graphs, Networks, and Trees
屬性
fromgives the identifier of the node which is adjacent from this arc.
狀態 必備的
資料類型 
data.pointer
值 The identifier of a node.
togives the identifier of the node which is adjacent to this arc.
狀態 必備的
資料類型 
data.pointer
值 The identifier of a node.
屬於graph
可包含
core: label
宣告
element arc
{
   att.global.attributes,
   attribute from { data.pointer },
   attribute to { data.pointer },
   ( label, label? )?
}
例子
<arc from="#T3" to="#T3">
 <label>OLD</label>
 <label>VIEUX</label>
</arc>
註
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.