Changes
In an industrial environment we quite often need to
* describe an industrial plant consisting of a bunch of different parts, each having a certain purpose and set of properties, and which are related in various ways
Therefore we need to
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[[File:UDOM_PlantParts.png|thumb|400px|alt=Parts of a plant|Example plant and parts]]
Lets start with a simple picture and assume that our plant consists of a pump and an armature. Both equipments exhibit certain technical or other properties, which our datamodel must contain in some form. Additionally the datamodel has to provide mechanism to indicate the circumstances that both equipments are parts of the plant and maybe even be related to each other.
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[[File:UDOM_TransitionMetaModel.png|thumb|400px|alt=Transition plant picture|Transition from plant picture into data model]]
The transition from the plant picture into an object- / data - model logically happens via an intermediate layer and finally leads to our first definition
An important aspect of the datamodel has not been discussed yet, namley <b>how are the blocks (=metaclasses) related to each other?</b> [[File:SmileyQuestion.png|20 px]]
Assuming that all three pumps are clearly parts of the plant „UBIK1“, the descriptive model has to be extended in order to include this information as well. In our "table" view we account for this by adding a property to the „Pump“ block refering to the plant. This additional property represents the link information between the pumps #1 - #3 and the plant „UBIK1“.
{{UMM|Data model built and described by metaclasses and metaproperties related to each other, either by <b>1 : n</b> or <b>n : n</b> cardinality.}}
[[File:UDOM_Relating4.png|thumb|400 px|alt=ER-model|Entitiy-Relationship-Model]]
In software engineering, such an abstract descriptive model is called Entity–Relationship model (ER model) and describes the entities (={{UBIK}} metaclasses) and relationships between them. Usually this information is depicted in an entitiy-relationship-diagram (ERD), which draws the corresponding data objects and relations as rectangles and lines between them, respectively. The metaclass ''„CONTROL“'' can be drawn as diamond, signalling the additional block between these two metaclasses, which is always needed for each relation of cardinality n : n.
[[File:UDOM_Relating5_RefRel.png|thumb|400 px|alt=References and Relations|{{UBIK}} References and Relations]]
Concluding and summarizing the above discussion we finally depict the two possible types of relation in the {{UBIK}} metamodel.
