tailieunhanh - PATTERNS OF DATA MODELING- P30

PATTERNS OF DATA MODELING- P30: 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. | Document 129 TangibleActor tangibleActorlD Customer customerlD salesData creditinformation discountschedules tangibleActorlD FK Figure Archetype Customer IDEF1X model. Figure Archetype Document UML model. A Document is a physical or electronic representation of a body of information. DocumentComposition enables a document to combine lesser documents. For example a product specification sheet may consist of various paragraphs pictures and tables. For a given document there may be no decomposition one level of decomposition or multiple levels of decomposition. DocumentComposition is a directed acyclic graph as some documents are reusable in multiple contexts. Note that DocumentComposition avoids symmetry see Chapter 8 with the distinction between parent and child. There is also DocumentFlow. A Document starts out as a concept ConceptualDoc and is then expressed in one or more languages LanguageDoc . For example a product specification sheet may have English German and Japanese translations. LanguageDocs can be parameterized a SpecificDoc assigns a value to each parameter. For example a LanguageDoc may have a picture of an electric motor with placeholders parameters for length and diameter the SpecificDoc specifies the actual length and diameter for each motor. And finally a SpecificDoc can be the basis for generating ConvertedDocs in formats such as PDF 130 Chapter 10 Archetypes Document DocComposition Figure Archetype Document IDEF1X model. HTML and XML. The model permits meaningless sequences but this explanation describes the intended flow and application code must enforce a proper sequence. Thus there is a flow to the progression of documents. Documents start out as concepts are expressed in various languages have parameters added and then are converted into the desired formats. Event An Event is an occurrence at some point in time Figure Figure . The notion of an event often appears in application models. An .