Extensions to query languages for graph traversal problems

Extensions to database query languages for retrievals that involve inferencing on the nodes and edges of a graph are surveyed. Common types of inferencing are to find paths between two nodes, compute a value for a path such as a distance or an elapsed time, and to choose among alternative paths. The survey is based on the data model (relational or functional), method of extension (iteration, recursion, or special operators), interface style (string or tabular), and restrictions (data- and problem-oriented). The Quel, objected-oriented functional data, G-Whin, and Alpha languages are examined in detail with different values for these properties. The characteristics of other languages are summarized in several tables. The results of the survey indicate the diversity of language extensions and the need to provide data-model and query-language features to address such problems