一种提高XML文档分发效率的封装策略

Efficient encapsulation strategy of content-based XML dissemination

每个路由器的路由表上所包含的订阅信息具有一定的关联性,现有的优化技术大多关注于单个路由器的效率,没有充分利用这一关联特性。结合目前常用的XPath订阅汇总技术,提出了两阶段封装策略生成头信息,并封装在文档的头部优化下游路由器的处理。传统的立即转发协议虽然可以加快分发过程,却不能充分生成和利用封装信息,基于封装的文档设计了一种将延迟转发和立即转发相结合的自适应的转发策略,从而充分利用了路由过程中订阅和匹配的关联性,提高了整个XML文档内容分发的性能,并给出了实验进行正确性验证。

Relevant subscriptions are stored in the routing tables in a Publish/Subscription （P/S） system. The already existing optimizations focus more on single router and didn＇t exploit from this. In this paper, the XPath subscription aggregation techniques were used and a 2-phase encapsulation strategy was proposed to generate a header of the XML to speed up the processing and matehing of the downstream router. Traditional immediate forwarding protocol can improve the dissemination by skipping the remaining processing after first match, but it can＇t get entire header to be used by the downstream router. An adaptive forwarding strategy was proposed to combine the immediate forwarding and delay forwarding together to give a full exploitation on the subscriptions and matching, and the whole dissemination efficiency of the P/S was consequently improved. Our experimental results demonstrate the correctness.