Abstract-We present a formal framework that enables us to analyze space complexity of automatic streaming processing of XML transformations. Within the framework, the classes of XML transformations as well as the streaming algorithms are represented as formal models. The efficiency of the algorithms designed is proved with mathematical rigor by simulations of transformation models by streaming models. Subsequently, we design an efficient stack-based streaming algorithm for processing top-down XML transformations. It demonstrates the usage of the framework, but at the same time it can be directly incorporated into applications if needed.