A graphical application development environment is provided, for the development of test, measurement and process control applications. Said environment comprises thematically organized groups of "panels" representing components of virtual instruments, and said panels are combined and interconnected via data channels, control channels and event channels to form a complete instrument "front panel." Each panel represents a quasi-autonomous "aspect" software object that has the attributes, properties and connectivities of the represented instrument component, and that is associated with executable code segments, including code segments that are usable by a plurality of aspects and are maintained in libraries accessible to an aspect handler for the construction of aspects. A representation of a user-developed application program, as created in a textual language, comprises an executable description of front panel aspects and their attributes and interconnections, and serves to invoke said associated code segments to run said user application.