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PATTERNS OF DATA MODELING- P39

PATTERNS OF DATA MODELING- P39: 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. | 13.4 Softcoding Variations 177 EntityType Attribute EnumValue entityTypeID attributeID entityTypeName AK1.1 dataType maxLength minMultiplicity maxMultiplicity - - d entityTypeID FK AK1.1 AK2.1 attributeName AK1.2 sequenceNumber AK2.2 defaultUnitOfMeasureID FK enumValueID valueInteger valueDecimal valueString valueDateTime attributeID FK AK1.1 sequenceNumber AK1.2 ----V------------------- I I I Entity entityID logicalIdentifier AK1.1 entityTypeID FK SoftcodedValue valueID valueInteger valueDecimal valueString valueDateTime dateOfEntry entityID FK attributeID FK overrideUOMID FK dataSourceID FK I UnitOfMeasure 1 __I__ unitOfMeasureID unitOfMeasName AK1.1 DataSource dataSourceID dataSourceName AK1.1 Figure 13.11 Softcoded values add value metadata IDEF1X model. 13.4.2 Cut Metadata A simplification is to forego metadata. This is essentially what the UML does with tagged values. Figure 13.12 and Figure 13.13 show the corresponding revision. In essence the model stores values without metadata. The advantage of omitting metadata is simplicity. The downside is that the values are less structured less controlled and more vulnerable to errors. This approach can be useful for a small amount of miscellaneous data but is not suitable for large quantities. Entity 1 SoftcodedValue logicalIdentifier valueInteger valueDecimal valueString valueDateTime attributeName Figure 13.12 Softcoded values cut metadata UML model. 178 Chapter 13 Softcoded Values Entity SoftcodedValue entitylD - -e valuelD logicalldentifier AK1.1 valuelnteger valueDecimal valueString valueDateTime attributeName entitylD FK Figure 13.13 Softcoded values cut metadata IDEF1X model. 13.4.3 Store All SoftcodedValues as Strings Figure 13.14 and Figure 13.15 show the option of storing all values as strings and converting them to the appropriate data type upon access. This simplifies the model at the cost of type conversions. Type conversions complicate programming and can introduce round-off errors. .