Systems development is becoming more and more complex. It consists of many phases such as high-level design, low-level design, design validation, simulation, and so on. Throughout the design process, a variety of tools are used to assist and automate the various phases. These tools are often incompatible, forcing the design phases to be performed in isolation. This limits the iterative possibilities of the design process and forces the designer to make commitments, such as hardware or software implementation, early in the design process. The Gravity system is a tool integration framework designed to provide continuity throughout the design process. It is intended to be used to build domain-specific design environments. Gravity provides an easy way to construct a common store of objects involved a design, and to apply various tools to these objects. New languages and tools can be easily integrated within the framework. The system makes no distinction between hardware and software modules, thereby facilitating hardware/software co-design. Gravity is implemented in JAVA, providing portability, networking capability and graphical extensibility.