Efficient and expressive tree filters

Abstract

We investigate streaming evaluation of filters on XML documents, evaluated both at the root node and at an arbitrary node. Motivated by applications in protocol processing, we are interested in algorithms that make one pass over the input, using space that is independent of the data and polynomial in the filter. We deal with a logic equivalent to the XPath language, and also an extension with an Until operator. We introduce restricted sublanguages based on looking only at "reversed" axes, and show that these allow polynomial space streaming implementations. We further show that these fragments are expressively complete. Our results make use of techniques developed for the study of Linear Temporal Logic, applied to XML filtering. © Springer-Verlag Berlin Heidelberg 2007.