tailieunhanh - PATTERNS OF DATA MODELING- P41

PATTERNS OF DATA MODELING- P41: Models provide the means for building quality software in a predictable manner. Models let developers think deeply about software and cope with large size and complexity. Developers can think abstractly before becoming enmeshed in the details of writing code. Although models are beneficial, they can be difficult to construct. That is where patterns come in. Patterns provide building blocks that help developers construct models faster and better. | Diagram Subject Area 187 Figure Example Data flow diagram for designing a database no ports . E1 Expansion valve C1 Compressor Figure Example Equipment flow diagram for an air conditioner with ports . Diagram Subject Area A generic diagram is a picture that conveys the meaning of the underlying model. Figure and Figure support discrete tabs for attaching lines. The gray shading is for entity types that involve metadata. An Icon is a picture that is symbolic of something. Examples of Icons include an oval in a data flow diagram and a compressor symbol in an equipment flow diagram. Each Icon has a name as well as a scale and position that are applied to its corresponding IconType. For example Figure has two Icons for heat exchangers IconTypes . One Icon is named Evaporator and the other Icon is named Condenser . Each Icon belongs to a specific Diagram. 188 Chapter 14 Generic Diagrams Figure Diagram subject area with tabs UML model. A generic diagram is a picture that suggests the meaning of the underlying model. Icon IconType Figure Diagram subject area with tabs IDEF1X model. Model Subject Area 189 A Tab is a discrete position on an Icon for attaching a Line. A Tab has a name as well as a scale and position that are applied to its corresponding TabType. The relationships between Tab and Line illustrate the Node-Edge directed graph see Chapter 3 . The relationships between Icon IconType Tab and TabType form a homomorphism see Chapter 5 . A Line is a means for coupling two Tabs. A Diagram is a set of Icons and Lines. Section defines DiagramType IconType TabType and LineType. Figure and Figure forego Tabs and permit lines to connect anywhere on an Icon. Figure Diagram subject area no tabs UML model. Icon Figure Diagram subject area no tabs IDEF1X model. IconType iconTypelD LineType lineTypelD Model Subject Area A semantic diagram has a model that expresses the meaning. Figure and .