Architectural Principles Discussion
Generalization and Subtypes
Generalization of subtypes is useful at a logical design level. Careful consideration will be given when mapping logical design to actual implementation. Generalization of subtypes can be used when a common structure is desirable across tables that may be implemented on an individual basis.
Example:
- LEGAL_LOCATION is a generalization of many of the specialized local grid systems, such as Dominion Land Survey, Texas Land Survey, and Congressional etc. For implementation purposes the individual subtypes have been projected as tables.
- WELL_TEST is another example of Generalization of drill stem and production tests. In this case the supertype WELL_TEST is implemented as a table.
Generalization is not useful when the concept that is being communicated becomes too abstract or vague.
Example:
- Drilling, Coring, Logging, Testing and Producing are all types of activities. However there is limited value in creating a supertype of ACTIVITY.
Object Technology
Although Relational Database technology has some shortcomings, it is nonetheless the most widely used information management platform, and provides adequate solutions to many important petroleum industry problems.
At present, there are no industry-wide standards for Object database specification, structure, or access languages. It is unlikely that the petroleum industry, which represents less than 5% of the worldwide database market, can or needs to significantly influence such standards.
It is expected that over the next 5 years the computer industry, particularly the major relational database vendors, will determine which parts of SQL3 are broadly adopted, and offer utilities to assist in migration from existing relational databases. Such determination will be no doubt based on technical feasibility and market demand.
PPDM will follow the SQL3 standards activities. When important new features providing technical benefit become widely available, with acceptable transition costs, we will advise the membership of this. With their concurrence, these features will then be adopted in a manner consistent with maximum upward compatibility and minimal cost of migration.
