Compression of double array structures for fixed length keywords

Trie is one of the data structures for keyword matching. The trie is used in natural language processing, IP address routing, and so on. It is represented by the matrix form, the link form, the double array, and LOUDS. The double array combines retrieval speed of the matrix form with compactness of the list form. LOUDS is a succinct data structure using bit-string. Retrieval speed of LOUDS is not faster than that of double array, but the dictionary size is smaller. This paper proposes a compression data structure of the double array by dividing trie into each depth and removing the BASE array from that double array. From experimental results, the retrieval speed was almost the same as double array, and the size of the presented method was the most compact in other methods including LOUDS for a large set of keywords with fixed length. Keywordstrie; double array; fixed length; compression