Understanding Data Modeling Methods: Graphical Syntax
Apress eBooks · 2006
SummaryWe covered some alternatives in data modeling graphic syntax languages, focusing on the IDEF1X notation we’ll use in all the models throughout this book. Many of the concepts that the symbols represent are the same. Although some symbols are unique to one style or another, the higher-level concepts are largely independent of the graphic symbol sets used in these languages. The symbols cover notations for many different aspects of set members and their attributes, which can be read as sentences when you know what the symbols represent. The symbols cover meaning for the following: Dependent (weak) and independent (strong) entities or tables Views and their dependencies on tables or other views Identifying and nonidentifying relationships or constraints Null ability of migrating keys Cardinality (how many allowed) of entity relationships Supertype and subtype category members Inclusive or exclusivity within category members Exclusivity between optional relationships Whether the category is complete or incomplete Primary key attributes and other owned attributes In the next chapter, we’ll cover how UML, an object-oriented modeling syntax with its own distinctive modeling symbols, relates to relational modeling.