Modeling "Numbers and Quantities" Correctly in Information Systems

"Numbers and Quantities" is one of the most fundamental yet underestimated topics in information system design. This talk focuses on the correct modeling and application of "quantities" in real-world systems, and how it should be properly integrated with Domain-Driven Design (DDD). While "numbers" are pure mathematical concepts, "quantities" carry business rules, units, precision, and cultural differences. From financial rounding and precision issues, manufacturing unit conversions and loss calculations, to medical multilingual processing and complex e-commerce order states, the correct modeling of quantities directly affects system stability, consistency, and maintainability. This talk will explore:

The essential differences between "numbers" and "quantities" Practical database techniques for handling quantities (custom types, domain events, materialized views, triggers) Common anti-patterns and lessons from real projects How DDD should work with database design instead of treating it as a mere implementation detail

The goal is to help developers and architects think more systematically about one of the most critical foundations in information systems.