The pq -gram distance between ordered labeled trees

• Published in: ACM transactions on database systems Vol. 35; no. 1; pp. 1 - 36
• Main Authors: Augsten, Nikolaus, Böhlen, Michael, Gamper, Johann
• Format: Journal Article
• Language: English
• Published: New York, NY Association for Computing Machinery 01.02.2010
• Subjects: Algorithmics. Computability. Computer arithmetics; Applied sciences; Approximation; Autonomous; Computer science; control theory; systems; Computer systems and distributed systems. User interface; Exact sciences and technology; Information systems. Data bases; Keys; Matching; Memory organisation. Data processing; Representations; Software; Theoretical computing; Trees; Lower bound; Input output; distance metric; similarity search; Scalability; XML language; tree edit distance; Tree structure; Graph theory; Weighted graph; Algorithms; approximate matching; hierarchical data; Database algorithms; XML; Database; Ordering; Experimentation; Metric; Graph labelling; Performance; Distance
• ISSN: 0362-5915; 1557-4644; 1557-4644
• DOI: 10.1145/1670243.1670247

When integrating data from autonomous sources, exact matches of data items that represent the same real-world object often fail due to a lack of common keys. Yet in many cases structural information is available and can be used to match such data. Typically the matching must be approximate since the representations in the sources differ. We propose pq -grams to approximately match hierarchical data from autonomous sources and define the pq -gram distance between ordered labeled trees as an effective and efficient approximation of the fanout weighted tree edit distance. We prove that the pq -gram distance is a lower bound of the fanout weighted tree edit distance and give a normalization of the pq -gram distance for which the triangle inequality holds. Experiments on synthetic and real-world data (residential addresses and XML) confirm the scalability of our approach and show the effectiveness of pq -grams.