Rewriting logic is both a flexible semantic framework within which widely different concurrent systems can be naturally specified and a logical framework in which widely different logics can be specified. Maude programs are exactly rewrite theories. Maude has also a formal environment of verification tools. Symbolic computation is a powerful technique for reasoning about the correctness of concurrent systems and for increasing the power of formal tools. We present several new symbolic features of Maude that enhance formal reasoning about Maude programs and the effectiveness of formal tools. They include: (i) very general unification modulo user-definable equational theories, and (ii) symbolic reachability analysis of concurrent systems using narrowing. The paper does not focus just on symbolic features: it also describes several other new Maude features, including: (iii) Maude's strategy language for controlling rewriting, and (iv) external objects that allow flexible interaction of Maude object-based concurrent systems with the external world. In particular, meta-interpreters are external objects encapsulating Maude interpreters that can interact with many other objects. To make the paper self-contained and give a reasonably complete language overview, we also review the basic Maude features for equational rewriting and rewriting with rules, Maude programming of concurrent object systems, and reflection. Furthermore, we include many examples illustrating all the Maude notions and features described in the paper.

重写逻辑既是一个灵活的语义框架，在其中可以自然地指定范围广泛的并发系统，又是一个逻辑框架，在其中可以指定范围广泛的逻辑。Maude程序完全是重写理论。毛德还拥有一个正式的验证工具环境。符号计算是一种强大的技术，可用于推理并发系统的正确性并提高形式化工具的功能。我们介绍了Maude的几个新的符号特征，这些特征增强了有关Maude程序的形式推理和形式工具的有效性。它们包括：（i）非常普遍的统一模用户自定义方程式的理论，以及（ii）象征性的可达性分析并发系统的使用范围缩小。本文不仅仅关注符号功能：还描述了Maude的其他一些新功能，包括：（iii）Maude的用于控制重写的策略语言，以及（iv）允许基于Maude对象的并发系统与Java的灵活交互的外部对象。外部世界。特别是元解释器是封装可以与许多其他对象进行交互的Maude解释器的外部对象。为了使本文自成一体并给出合理的语言概述，我们还回顾了Maude的基本功能，用于方程式重写和规则重写，并发对象系统的Maude编程以及反射。此外，我们包括许多示例，这些示例说明了本文中描述的所有Maude概念和功能。