Open Source Java Stream Processing Tools

MXQuery is a low-footprint implementation of XQuery 1.0, XQuery Update 1.0, XQuery Fulltext 1.0 and XQuery Scripting 1.0 as well as a subset of XQuery 1.1 (windowing, try/catch). It provides extensions to do data stream processing/CEP and SOAP/REST

Build applications that respond immediately to events. Craft materialized views over streams. Receive real-time push updates, or pull current state on demand. Seamlessly leverage your existing Apache Kafka® infrastructure to deploy stream-processing workloads and bring powerful new capabilities to your applications. Use a familiar, lightweight syntax to pack a powerful punch. Capture, process, and serve queries using only SQL. No other languages or services are required. ksqlDB enables you to build event streaming applications leveraging your familiarity with relational databases. Three categories are foundational to building an application: collections, stream processing, and queries. Streams are immutable, append-only sequences of events. They're useful for representing a series of historical facts. Tables are mutable collections of events. They let you represent the latest version of each value per key.