A metrics based design method and system is disclosed. The method includes receiving by a computer processor, an informational model comprising data objects, attributes, and relationships associated with a service. The data objects comprise sub-objects. The computer processor receives business affinity (BA) band data associated with the data objects, threshold levels associated with the business affinity (BA) band data, business affinity (BA) levels associated with the business affinity (BA) band data, and service interface operation parameters. The computer processor computes a business affinity (BA) for the informational model based on the business affinity (BA) band data, the threshold levels, the business affinity (BA) levels, and the service interface operation parameters. The computer processor computes a data variation percentage and a reusability count. The computer processor performs: a nested level computation for service valency, a factorization process for computing service valency, and a data element count.