STX (Streaming Transformations for XML) can be used to split a document into fragments and transfer the processing of these fragments to external SAX filter components. This approach is useful if neither a pure streaming technique (e.g. STX) nor a pure tree-based technique (e.g. XSLT) are appropriate processing models. The talk will give a short introduction to STX, show its integration from the Java application point of view, and demonstrate the implementation of custom SAX filters that can be plugged into the STX engine Joost. The capability of modifying filter code before applying it will be shown using Schematron as an example.