PCB Logical design data is stored in a database according to a connectivity-based data model. Circuit functional blocks, inputs and outputs of functional blocks, and signals are stored as separate data structures. Those structures may be edited by users at separate clients during concurrent editing sessions. Profile data for each of multiple users specifies logical design data elements accessible by, and PCB design software to be provided to, that user. The PCB design software may be plug-ins executable within a web browser at a client, and the client computers may communicate with the database via the Internet. Layout data may also be stored in the database, with elements of the layout data mapped to elements of the logical design data. Constraint data may also be stored in the database, with elements of the constraint data being mapped to elements of the layout data.