Most languages in Model Driven Engineering (MDE) are defined by metamodels. Metamodels specify the structural aspects of models but do not capture the computational meaning of the modeling constructs (the dynamic semantics). There are several semantic definition frameworks used for programming languages. In this paper we study the suitability of Action Semantics proposed by P.D. Mosses for defining dynamic semantics for modeling languages. Action Semantics provides an intuitive textual notation and allows modular semantic specifications. However, it is originally proposed for grammar-based languages. The application of Action Semantics to metamodel-based languages requires studying how the action notation can be used with graph structures. We built a compiler that translates models to action trees and a simulator that executes action trees. In this way models become executable and their behavior can be studied at an early modeling phase. We implemented several examples to gain experience of using Action Semantics for modeling languages.