We present a new web-based, client-server data processing and visualization framework that supports a flexible workflow, enabling the user to customize different data processing and visualization tasks with tools implemented in different programming languages. Our framework supports server-side applications developed with different languages, allowing visualization researchers to easily make their new techniques available to the target users. The client-side of our framework is implemented in the web browser environment with customizable interface and visualizations. We describe the design of the architecture of our framework and the process of adding new user-defined tasks, followed by the demonstration of the proposed framework on a number of data processing and visualization tasks.