CJK Experiments with Hummingbird SearchServerTM at NTCIR-5

Hummingbird submitted ranked result sets for the Chinese, Japanese and Korean Single Language Information Retrieval subtasks of the Cross-Lingual Information Retrieval Task of the 5th NII-NACSIS Test Collection for IR Systems Workshop (NTCIR-5). For short Chinese (title) queries, a decompounded wordbased approach produced higher (statistically significant) mean average precision and first relevant scores than an overlapping n-gram approach. For Korean queries, a word-based decompounding and stemming approach produced significantly higher mean average precision scores than plain word-based matching. For Japanese title queries, a blind feedback technique which produced a statistically significant increase in mean average precision also produced a statistically significant decrease in mean first relevant score.