Section: Research Program

Pattern mining algorithms

Twenty years of research in pattern mining have resulted in efficient approaches to handle the algorithmic complexity of the problem. Existing algorithms are now able to efficiently extract patterns with complex structures (ex: sequences, graphs, co-variations) from large datasets. However, when dealing with large, real world datasets, these methods still output a huge set of patterns, which is impractical for human analysis. This problem is called pattern explosion. The ongoing challenge of pattern mining research is to extract fewer but more meaningful patterns. The Lacodam team is committed to solve the pattern explosion problem following four research topics:

• the design of dedicated algorithms for mining temporal patterns

• the design of flexible pattern mining approaches

• the selection of interesting data mining results

• the design of parallel pattern algorithms to ensure scalability

The originality of our contributions relies on the exploration of knowledge-based approaches whose principle is to incorporate dedicated domain knowledge (aka application background knowledge) deep into the mining process. While most of the data mining approaches are based on agnostic approaches that are designed to cope with the pattern explosion, we propose to develop data mining techniques relying on knowledge-based artificial intelligence techniques. This covers the use of structured knowledge representations, as well as reasoning methods, in combination with mining.

The first approach concerns the classical approach of pattern mining which consists in using expert knowledge to define new pattern types (and related algorithms) that can solve applicative issues. In particular, we investigate how to handle temporality in pattern representations which turns out to be important in many real world applications (in particular for decision support) and deserves particular attention.

The two other approaches aim at proposing alternative pattern mining methods to let the user incorporate, by her own, knowledge that will help define her pattern domain of interest. Flexible pattern mining approaches enable analysts to easily incorporate extra knowledge, for example domain related constraints, in order to extract only the most relevant patterns. On the other hand, the selection of interesting data mining results aims at devising strategies to filter out the results that are useless for the data analyst. Beside the challenge related to algorithmic efficiency of such approaches, we are interested in formalizing the foundations of interestingness, according to background knowledge modeled with logic knowledge representation paradigms.

Last, pattern mining algorithms are computation-intensive, it is thus important to exploit all the available computing power. Parallelism is for a foreseeable future one of the main ways to speed up computations, and we have a strong competence on the design of parallel pattern mining algorithms. We will exploit this competence in order to guarantee that our approaches scale up to the real data provided by our partners.