Through theoretical analysis and experimental verification,a phenomena called the exploration-exploitation dilemma is proved to exist in pheromone trail updating and a novel pheromone trail updating strategy is presented on the basis of the Metropolis rule.

This paper discusses the virtues and shortcomings of the re-merge strategy,in-place strategy and hybrid strategy,and presents an improved hybrid index update strategy with multilevel that combines the virtue of previous methods together.

One Webpage Refresh Strategy According to Popularity and Freshness;