臺大管理論叢 NTU Management Review VOL.28 NO.3

Use of Implicit User Feedback to Support Semantics-Based Personalized Document Recommendation 92 To spread the concepts of interest, the ICE technique employs the generalization, specialization, and relevance expansion strategies. Generalization expansion is the activation of the generalized concepts of the focal concept (e.g., activating the concept of “Hardware” from that of “Memory Structure”). Specialization expansion is the activation of the specialized concepts of the focal concept (i.e., activating the concept of “Memory Structure” from that of “Hardware”). Relevance expansion is the activation of the concepts that maintain a non-is-a relationship with the focal concept. Each expansion strategy is assigned a weight between 0 and 1 to simulate the decreasing interest of the expanded relevant concepts. In this study, we set the generalization, specialization, and relevance expansion weights at 0.7, 0.4, and 0.5, respectively. The following three parameters are essential to the process of concept expansion: activation value, spreading distance, and spreading threshold. The activation value is the interest score of a concept, which is initially set to 0. The spreading distance and the spreading threshold are related to the stopping condition of concept expansion. The spreading distance is the maximum step by which the focal concept can spread, and the spreading threshold is the minimum activation value by which a concept can be further expanded. The expansion process terminates as all expanded concepts reach the maximum spreading step or all their activation values are less than the spreading threshold. In this study, we set the spreading distance and the spreading threshold to 2 and 0, respectively. Figure 2 Example of Domain Concept Heterarchy 1. Hardware 1.1 Memory Structures 1.1.1 Semiconductor Memories 1.1.2.1 Primary Memory 1.2 Logic Design 1.2.2 Design Aids Non-is-a relationship Is-a relationship 1.1.2 Design Styles 1.2.1 Design Styles