We propose a scaleable multi-user benchmark called XMach-1 (XML Data Management benchmark) for evaluating the performance of XML data management systems. It is based on a web application and considers different types of XML data, in particular text documents, schema-less data and structured data. We specify the structure of the benchmark database and the generation of its contents. Furthermore, we define a mix of XML queries and update opera-tions for which system performance is determined. The primary performance metric, Xqps, measures the query throughput of a system under response time constraints. We will use XMach-1 to evaluate both native XML data management systems and XML-enabled relational DBMS.