It might be intractable to compute a generic SRK; Bu et al. further propose a sub-class of SRK, called kb-SRK, which can be computed efficiently. Experimental results show that the use of kb-SRK can achieve results comparable with the state-of-the-art methods on paraphrase identification and recognizing textual entailment.
Their paper received the best student paper award at ACL 2012.
The article can be found here PDF.