Thus, (Franconi et al., 2010a) defines a query linearisation as a strict total order 2 on the query tree that satisfies the following conditions: • all labels associated with the edge's leaving node precede the edge label • the edge label is followed by at least one label associated with the edge's arriving node • between any two labels of a node there can only be (distinct) labels of the same node The specific linearisation adopted in Quelo is defined by the depth-first traversal strategy of the query tree and a total order on the children which is based on the query operations.
the labels of a node are ordered according to the sequence applications of the add compatible concept operation.