The Janus Term

• Janus is the Roman god of doorways as well as beginnings & endings
• Thus the two faces, looking backwards and forwards
• This has little to do with my topic
• But I'm trying to appear educated
• "Data model" has two meanings
• First is the representation of a set of business rules for a data management system
• Tables and constraints for SQL are a "data model" of some business domain
• The other is general theory of representing and manipulating data
• I'm going to talk about this meaning