PPT Slide
System Concepts for Data Modeling
- Attributes
- Identification:
- Sometimes, it is also necessary to identify a subset of entity instances as opposed to a single instance.
- For example, we may require a simple way to identify all male students, and all female students.
- A subsetting criteria is a attribute (or concatenated attribute) whose finite values divide all entity instances into useful subsets. Some methods call this an inversion entry.