Silver is an attribute grammar (AG) specification language and evaluator. What makes Silver unique among attribute grammar tools is that it is designed to support the specification of extensible language and is itself extensible. Thus general purpose and domain specific features can be easily added to it. Thus, it supports a myriad of attribute grammar features that are found separately in different AG systems.
These features include higher-order attributes, reference attributes, collection attributes, forwarding, aspect productions, and numerous convenience features. Various general purpose language features can also be added as extensions. These include pattern-matching and parametric polymorphism which dramatically simplify the specification of general purpose computations in Silver.