Part V

Canonical Models

Part V presents several canonical models — models that often appear and cut across individual applications. These models are services with logic that stands apart from the various applications that use them. The canonical models contrast with the archetypes, in that archetypes revolve around a basic concept found in models, while canonical models are complete models that can be used as part of a larger application.

Chapter 12 presents several approaches to the translation of human languages. Software that is written for international markets must be able to support multiple languages such as English, Spanish, and Chinese. Data can often be stored in the language of entry, but there is a need to translate metadata, such as labels in forms and reports.

Chapter 13 covers softcoded values. The usual approach is to hardcode attributes in entity types and the resulting tables. As an alternative, values can be softcoded — metadata specifies the intended model and generic tables store the values. Softcoded values are appropriate for applications with uncertain data structure; softcoding adds stability to the data representation, minimizes changes to application logic, and reduces the likelihood of data conversion. On the downside, softcoded values add complexity and incur a modest performance penalty.

Chapter 14 discusses generic diagrams, diagrams that display as a picture and have underlying semantic content. The generic diagram model provides a starting point for various kinds of diagrams such as data structure diagrams, data flow diagrams, state diagrams, and equipment flow diagrams.

Chapter 15 explains state diagrams for specifying states and stimuli that cause changes of state. State diagrams are helpful for applications with a lifecycle or a sequence of steps to enforce. Such information can be declared in database tables, rather than encoded via programming. One group of tables specifies state diagrams that generic code interprets. Another set of tables can store data from an application’s execution of state diagrams.

The canonical models have some complexity that illustrates the power of modeling. They leverage some of the patterns shown in earlier chapters.