MOD/R models all views on the design space in relations. This is achieved by eliminating the package constraints, as are apparent in PCB oriented hardware description languages. Assisted by knowledge engineering it allows for a top-down, mostly hierarchical decomposition, virtually eliminating the need for bottom-up assembly.
Spaanenburg, L., Beunder, M., Beune, F. A., Gerez, S. H., Holstein, B., Luchtmeyer, R. C. C., ... Willems, H. (1985). MOD/R : A knowledge assisted approach towards top-down only CMOS VLSI design. Microprocessing and Microprogramming, 16(2-3), 83-88. https://doi.org/10.1016/0165-6074(85)90043-2