a traversal method having a memory for storing tree structure data having nodes , each node including an attribute indicating a traversal stage in the tree structure in which an evaluation result of an attribute corresponding to the traversal state of each node of the tree structure data is stepwise arranged according to a depth - first order in the memory in a sequential fashion , the memory including two memories . in this method , the system recognizes as a sub - tree a group of nodes which have a same kind and which are linked with each other , sequentially arranges , during a traversal of a root of the sub - tree , symbols indicating an initiate position of the sub - tree and an end position thereof , and a symbol indicating an intermediate position of the sub - tree in a first memory . the system copies , while searching a series of data thus sequentially arranged for each kind , the initiate symbol , the intermediate symbol , and the end symbol of the sub - tree not belonging to the kind onto second memory . when the initiate symbol of a sub - tree belonging to the kind is detected , an activation of a traversal of the sub - tree is indicated , and when the intermediate and end symbols are detected , a reactivation of a traversal of the sub - tree is indicated . in response to the indication , a traversal of the sub - tree belonging to the kind is executed so as to develop an attribute of the sub - tree in the second memory .