In the spec of DirContext.search(Name name, String filterExpr, Object[] filterArgs, SearchControls cons), we did not tell the details of the sytax of filterExpr. We just said that, "The interpretation of filterExpr is based on RFC 2254". As is not instructive to developers and they might not look into the RFC for the complete syntax. In practice, we have found some illegal usage of the filter. To help the developers understanding the filter syntax easier, we need to make improvement to include some key points of the filters syntax in the method specification, and a detailed one in the JNDI tutorials.