SOAP Processing: A Non-extractive Approach

Abstract

As the first step of most XML processing algorithms, one usually extracts token content out of the source document into many discrete string objects. We propose a “non-extractive” tokenization approach that maintains the source document intact in memory. Using a binary encoding specification called Virtual Token Descriptor (VTD), the processing model represents tokens exclusively using starting offset and length. To create a hierarchical view of the data encapsulated in the SOAP message, the parser further indexes elements of same depths using directory-like structures we call location cache. Through a demonstration of navigating the document hierarchy using VTD and location caches, we show that it is indeed possible to create a cursor-based API that retains most of DOM’s random-access capabilities at a fraction of its memory usage. Furthermore, by analyzing key design constraints of custom hardware, we reason that the memory conserving characteristics of the processing model simultaneously make possible “SOAP on a chip” and “binary-enhanced SOAP.” The benchmark results show that the reference implementation of our processing model significantly outperforms Xerces DOM in terms of both memory and processing performance.