Abstract: A subject-oriented graphical programming environment, for the design and construction of virtual instrumentation systems, comprises means enabling the visualization of data sources, control sources, data sinks, and events, thereby maximizing hardware device interchangeability and allowing device simulation. Said means comprise a decoupling software layer for decoupling the data connection aspects of a development environment from its visualization, data processing and control components. The decoupling layer comprises a “Jack” component type, to interface with the data connection components of an application, linkable to a “Plug” type component that interfaces with the rest of the application. Jack and Plug components are configurable by application developers using graphical tools, providing users with broad discretion to define their own data acquisition virtual interfaces, rather than being limited to using an existing data connection component directly.