Business PME is a gate of free information bound for the companies in the United States of America. This website offers thousands of contents as well as a companies directory.
The group’s other BtoB websites
-- Professional Networking
Tursday March 18th 2010
Searcharticles Search
companies
- Strategy
- Marketing
- Advertising
- Trade
- Human Ress.
- Law & Rights
- Economics
- Finance
- Production
- Technologies
Generic Data Modeling | ||
Different modelers may well produce different models of the same domain. This can lead to difficulty in bringing the models of different people together. Invariably, however, this difference is attributable to different levels of abstraction in the models. If the modelers agree on certain elements which are to be rendered more concretely, then the differences become less significant. There are generic patterns that can be used to advantage for modeling business. These include the concepts PARTY (with included PERSON and ORGANIZATION), PRODUCT TYPE, PRODUCT INSTANCE, ACTIVITY TYPE, ACTIVITY INSTANCE, CONTRACT, GEOGRAPHIC AREA, and SITE. A model which explicitly includes versions of these entity classes will be both reasonably robust and reasonably easy to understand. More abstract models are suitable for general purpose tools, and consist of variations on THING and THING TYPE, with all actual data being instances of these. Such abstract models are significantly more difficult to manage, since they are not very expressive of real world things. More concrete and specific data models will risk having to change as the environment changes. One approach to generic data modeling has the following characteristics...* A generic data model shall consist of generic entity types, such as 'individual thing', 'class', 'relationship', and possibly a number of their subtypes. * Every individual thing is an instance of a generic entity called 'individual thing' or one of its subtypes. * Every individual thing is explicitly classified by a kind of thing ('class') using an explicit classification relationship. * The classes used for that classification are separately defined as standard instances of the entity 'class' or one of its subtypes, such as 'class of relationship'. These standard classes are usually called 'reference data'. This means that domain specific knowledge is captured in those standard instances and not as entity types. For example, concepts such as car, wheel, building, ship, and also temperature, length, etc. are standard instances. But also standard types of relationship, such as 'is composed of' and 'is involved in' can be defined as standard instances. This way of modeling allows to add standard classes and standard relation types as data (instances), which makes the data model flexible and prevents data model changes when the scope of the application changes. A generic data model obeys the following rules...* 1. Candidate attributes are treated as representing relationships to other entity types. * 2. Entity types are represented, and be named after, the underlying nature of a thing, not the role it plays in a particular context. Entity types are chosen * 3. Entities have a local identifier within a database or exchange file. These should be artificial and managed to be unique. Relationships are not used as part of the local identifier. * 4. Activities, relationships and event-effects are represented by entity types (not attributes). * 5. Entity types are part of a sub-type/super-type hierarchy of entity types, in order to define a universal context for the model. As types of relationships are also entity types they are also arranged in a sub-type/super-type hierarchy of types of relationship. * 6. Types of relationships are defined on a high (generic) level, being the highest level where the type of relationship is still valid. For example, a composition relationship (indicated by the phrase: 'is composed of') is defined as a relationship between an 'individual thing' and another 'individual thing' (and not just between e.g. an order and an order line). This generic level means that the type of relation may in principle be applied between any individual thing and any other individual thing. Additional constraints are defined in the 'reference data', being standard instances of relationships between kinds of things. Examples of generic data models are ISO 10303-221, ISO 15926 and Gellish Copyright 2008 - France BtoB from Wikipédia
|
• Duties of a database
• Cookies • INMOS Company • Overview of ERP • Dell computers Company • Data processor • Computer-aided manufacturing | |
