Abstract: In the present paper is proposesd an incremental index structure used in web search engine in orderto deal with the high update frequency of the web pages crawled by domainspecific crawler. In the inverted index structure, the posting list of each term is partitioned into linked blocks, whose sizes form an arithmeticalseries. The incremental index structure resolves the problem of document update, which is expensive in inverted index of continuous storage, and experimental results show that it provides much higher retrieval efficiency than naive linked list structure, which also supports realtime update. The spacefortime approach effectively raises the update rate of index.

Key words: domainspecific search engine, incremental inverted index, realtime update