To improve the query performance over XML documents in a distributed environment, we develop a semantic caching system named ACE-XQ for XQuery queries. ACE-XQ applies innovative query containment and rewriting techniques to answer user queries using cached queries. We also design a fine-grained replacement strategy which records user access statistics at a finer granularity than the complete XML query regions. As a result, less frequently used XML view fragments are replaced to maintain a better utilization of the cache space. Extensive experimental results illustrate the performance improvement achieved by this strategy over the traditional one for a variety of situations.