Helsinki Institute for Information Technology

About: Helsinki Institute for Information Technology is a facility organization based out in Espoo, Finland. It is known for research contribution in the topics: Population & Bayesian network. The organization has 630 authors who have published 1962 publications receiving 63426 citations.

A framework for path-oriented network simplification

Abstract: We propose a generic framework and methods for simplification of large networks. The methods can be used to improve the understandability of a given network, to complement user-centric analysis methods, or as a pre-processing step for computationally more complex methods. The approach is path-oriented: edges are pruned while keeping the original quality of best paths between all pairs of nodes (but not necessarily all best paths). The framework is applicable to different kinds of graphs (for instance flow networks and random graphs) and connections can be measured in different ways (for instance by the shortest path, maximum flow, or maximum probability). It has relative neighborhood graphs, spanning trees, and certain Pathfinder graphs as its special cases. We give four algorithmic variants and report on experiments with 60 real biological networks. The simplification methods are part of on-going projects for intelligent analysis of networked information.

Learning bounded tree-width Bayesian networks using integer linear programming

Abstract: In many applications one wants to compute conditional probabilities given a Bayesian network. This inference problem is NP-hard in general but becomes tractable when the network has low tree-width. Since the inference problem is common in many application areas, we provide a practical algorithm for learning bounded tree-width Bayesian networks. We cast this problem as an integer linear program (ILP). The program can be solved by an anytime algorithm which provides upper bounds to assess the quality of the found solutions. A key component of our program is a novel integer linear formulation for bounding tree-width of a graph. Our tests clearly indicate that our approach works in practice, as our implementation was able to find an optimal or nearly optimal network for most of the data sets.

Subset Sum in the Absence of Concentration

Abstract: We study the exact time complexity of the Subset Sum problem. Our focus is on instances that lack additive structure in the sense that the sums one can form from the subsets of the given integers a ...

Using dramaturgical methods to gain more dynamic user understanding in user-centered design

Abstract: In this paper we introduce the method of dramaturgical reading, which was originally a method of producing different crystallized and associative theatrical and graphical presentations of a role character in a drama context. We transfer dramaturgical reading into the field of user-centered design in order to understand, analyze and represent user-centered material. We compare a persona created with dramaturgical reading to a user profile and persona. We state that adapting a role character as an embodied and concrete user description in user-centered design improves the designers' ability to empathize and understand the users, thus improving the results of the design process. We believe personas must be enabled to "come to life" and allowed to develop in the minds of the designers using them. The dramaturgical method is one way of accomplishing this.