The original publication is available at www.springerlink.comRecent work on incremental crawling has enabled the indexed document collection of a
search engine to be more synchronized with the changing World Wide Web. However, this
synchronized collection is not immediately searchable, because the keyword index is rebuilt
from scratch less frequently than the collection can be refreshed. An inverted index is usually
used to index documents crawled from the web. Complete index rebuild at high frequency is
expensive. Previous work on incremental inverted index updates have been restricted to adding
and removing documents. Updating the inverted index for previously indexed documents that
have changed has not been addressed.
In this paper, we propose an efficient method to update the inverted index for previously
indexed documents whose contents have changed. Our method uses the idea of landmarks
together with the diff algorithm to significantly reduce the number of postings in the inverted
index that need to be updated. Our experiments verify that our landmark-diff method results
in significant savings in the number of update operations on the inverted index
