In urban planning and land use, "MDR" is a common designation for zoning that allows for multi-family housing like townhomes or small apartment complexes.
Often used in industrial documentation to refer to storage tanks (e.g., fuel, water, or chemical tanks) or specific technical drawings associated with them. Download MDR SELM TNK zip
A data packet from a municipal planning department (like San Bernardino County or similar) containing maps or environmental assessments for "MDR" developments. How to Locate the Correct File In urban planning and land use, "MDR" is
Since this appears to be a specific project file rather than public software: In urban planning and land use