MD050 is the Functional Design Document and 
MD070 is the Technical Design Document.

For any component like Report, Interface etc we have to 
first get the requirements as to what is the source , 
destinations, what data should be moved and what functional 
validations would be required etc. All this would go into 
the MD050. Generally written by non-technical people like 
Business Analysts or Functional Consultants.

MD070 is the technical document that is written to fulfill 
the functional requirement specified in MD050. It includes 
the approaches you take, pseudocode, Validations, Data 
Sources, SQL Statements etc.

Thanks,

R C Pandre