Megumi Ishii

Simplification of majority‐voting classifiers using binary decision diagrams

Various versions of the majority-voting classification method have been proposed in recent years as a strategy for improving classification performance. This method generates multiple decision trees from training examples and performs majority voting of classification results from these decision trees in order to classify test examples. In this method, however, since the target concept is represented in multiple decision trees, its readability is poor. This property makes it ineffective in knowledge-base construction. To enable the majority-voting classification method to be applied to knowledge-base construction, this paper proposes a simplification method that converts the entire majority-voting classifier into compact disjunctive normal form (DNF) formulas. A significant feature of this method is the use of binary decision diagrams (BDDs) as internal expressions in the conversion process to achieve high-speed simplification. A problem that must be addressed here is the BDD input variable ordering scheme. This paper proposes an ordering scheme based on the order of variables in the decision trees. The simplification method has been applied to several real-world data sets of the Irvine Database and to data from medical diagnosis domain. It was found that the description size of the majority-voting classifier after simplification was on the average from 1.2 to 2.7 times that of a single decision tree and was less than one-third the size of a majority-voting classifier before simplification. Therefore, the method is effective in reducing the description size and should be applicable to the knowledge acquisition process. Using the input variable ordering scheme proposed here, high-speed simplification of several seconds to several tens of seconds is achieved on a Sun SPARC-server 10 workstation.

Interactive constraint satisfaction for office systems

This paper presents an interactive constraint satisfaction mechanism for building office systems. We noticed that regulations for business are primarily described in declarative constraints, and clerical work could be regarded as consistency maintenance governed by conformance to the regulations in terms of the data in business databases and application forms. From this view point, we model clerical work as a consistency maintenance model. On the basis of the model, we develop a constraint syntax and an interactive constraint satisfaction system appropriate to clerical work. In order to demonstrate the validity and effectiveness of our method, we rewrote the general affairs expert system KOA, an office system currently in operation, using constraints, and evaluated the resulting performance. Experimental results show that all the regulations can be easily described in constraints, the description size is reduced by 50%. The constraints have high modularity and cover rare cases exhaustively, the response time is short enough to be feasible, and the number of interactions is almost equivalent to that of the original system. The results confirm the important point that we can easily realize a maintainable office system with the interactive constraint satisfaction mechanism without increasing the number of interactions.<<ETX>>

INTERFACER: a user interface tool for interactive expert-systems

Abstract From the user interface point of view, expert-systems are different from conventional applications in some features. First, the user query sequence highly depends upon input data up to that time. Second, any change in query sequence requires highly complicated data modification routines. Thus, user interface implementation is a bottleneck in the same manner as knowledge acquisition is the bottleneck for expert-systems. To resolve this problem, this paper proposes the user interface tool “INTERFACER” for interactive expert-systems. INTERFACER automatically generates a user interface screen according to the data input query requirement from the inference engine, and requires no user data modification routines in expert-system development. We applied the proposed INTERFACER to a practical middle-scale business system: The General Employee Affairs Expert-system. Program amount was decreased 50% compared to the conventional procedural implementation.

A constraint-satisfaction approach to clerical work

The authors present a constraint satisfaction mechanism for office systems. Describing clerical work with a consistency maintenance model, they have developed a constraint syntax and an interactive constraint satisfaction engine for clerical work. They have used constraints to rewrite an operational office system.

A revision learner to acquire verb selection rules from human-made rules and examples

This paper proposes a learning method that automatically acquires English verb selection rules for machine translation using a machine learning technique. When learning from real translation examples alone, many examples are needed to achieve good translation quality. It is, however, difficult to gather a sufficiently large number of real translation examples. The main causes are verbs of low frequency and the frequent usage of the same sentences. To resolve this problem, the proposed method learns English verb selection rules from hand-made translation rules and a small number of real translation examples. The proposed method has two steps: generating artificial examples from the hand-made rules, and then putting those artificial examples and real examples into an internal learner as the training set. The internal learner outputs the final rules with improved verb selection accuracy. The most notable feature of the proposed learner is that any attribute-type learning algorithm can be adopted as the internal learner. To evaluate the validity of the proposed learner, English verb selection rules of NTTs Japanese-English Machine Translation System ALT-J/E are experimentally learned from hand-made rules and real examples. The resultant rules have better accuracy than either those constructed from the real examples or those that are hand-made.