XLang is the core technology behind the open-source low-code Nop platform, designed for rapid Domain-Specific Language (DSL) creation. It replaces traditional map-based structures with a tree model using an `x-extends` operation, adding reverse-deletion semantics. This shift supports Reversible Computation, a paradigm where system state is expressed as `Y = F(X) + Delta`, allowing incremental, reversible changes.

The language's primary purpose is enabling Language-Oriented Programming, where developers build custom DSLs for specific business domains. XLang simplifies this by letting users define a DSL with a single XDef metamodel file. The Nop platform then automatically generates parsers, validators, and IntelliJ IDEA plugins for syntax support. A key innovation is the built-in Delta customization mechanism, which lets users modify logic by adding Delta files without touching the original source code.

This approach aims to solve coarse-grained software reuse in enterprise environments. For example, a core banking system built with XLang can be customized across the entire stack—from data models to frontend displays—solely through Delta files. The language's theoretical basis draws from mathematics and physics, which can create cognitive friction for developers trained only in computer science, but it offers a unified structural layer for system evolution.