TAILIEUCHUNG - PATTERNS OF DATA MODELING- P16

PATTERNS OF DATA MODELING- P16: 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. | 56 Chapter 3 Directed Graph Template same time. For example a chief information officer may report to both the chief operating officer and chief financial officer. The model can store the current reporting structure reporting structures of the past and planned structures of the future. The structure changes as persons join and leave a company. The structure also changes due to promotions and demotions and management changes. Figure Simple DG changing over time Evolving matrix management model. Node and Edge DG Changing over Time Template This template adds time intervals to the Node and Edge entity types from Section . UML Template Figure shows the template for node and edge directed graphs that change over time. Unlike the simple directed graph changing over time Figure does not separate an entity from its position in a directed graph. It is not clear how to make such a distinction with nodes and edges as peer concepts I have not needed such a distinction in practice. Figure Node and edge directed graph changing over time UML template. Use when there is data for edges and history must be recorded. A DG directed graph is a set of nodes and a set of directed edges that connect nodes. Note in a directed graph all the nodes need not be connected. You need not show DG in a Node and Edge DG Changing over Time Template 57 use of the template. A Node is an entity type whose records are organized as a directed graph. An Edge is a coupling from a source Node to a sink Node. With this template the names of nodes and edges are globally unique. There is no context to provide an alternative approach to naming. IDEF1X Template Figure restates Figure with the IDEF1X notation. The following are foreign keys dgID references DG sourceNodelD references Node and sinkNodelD references Node. Similar to Section we allow node and edge names to change over time. Node DG nodeID Edge JdgID L-------J edgeID dgID FK nodeName .

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