As described in the section on Classes and Instances and Entities, Entities are things that may be physical or abstract. Entities have attributes, and values for these attributes.
In LegendBurster, both mapObjects and queries are top level entities in the ontology.
In the Ontology Editor, we create for these top-level entities all the attributes necessary to describe them, we link them to their attributes, and we create value domains for the attributes, if appropriate.
Creating Entities from Attributes
As soon, however, as our description of the top level entities (mapObjects or queries) needs to be more than one level deep, we can adopt a new perspective on the first level attribute/value pair - and recognise that they can also be regarded as entities, and can therefore have attributes of their own, as illustrated in the following diagram:
To give them this capability, we simply declare the attribute to be an entity as well, using the "Create Entity" button in the Ontology Editor, followed by the "Create Entity based on Existing Attribute" option, as shown below:
In the above example, as soon as one clicks on the button labelled "Entity Name based on existing Attribute", all existing attributes are shown in area (2). One of these is selected, a descriptive comment entered, and the process concluded by clicking on "Create".
If the "Entity Name from word-list" option is chosen, the current word list appears in region (2), and region (5) shows the text-strings within which any selected word is used in the shapefile dbf table.
The first option in area (1) would be used if an entity was needed whose name came from a value domain. (Example: The entity "fault", which is shown to have value attributes in the section on "Attributes: Types and Naming", would have been created with this option. <View the example>)
Creating Entities which are "Reified Attributes"
Reification attributes are a special class of entities/attributes whose names are arbitrary, and which simply serve as identifiers for collections of attributes. Their values are not relevant to similarity measures when evaluating queries, but they are important in communicating descriptions and evaluating the results of queries. Reified Attributes are described in a section of the Appendix entitled "Representing Complex Entity-Attribute-Value Associations".
Reified attributes are created automatically from the "Create Attribute" form when the "Reify" box is selected.
Entities which give rise to "Value Attributes"
If a defined entity also exists as a value in a value domain, then, if the value is displayed in the Values column of the Ontology Editor, and selected, its attributes will be displayed in the Value Attributes column of the Ontology Editor. <View Example>
How Value Attributes arise is fully explained in the section on "Attributes: Types and Naming"
Proceed to "Attributes: Types and Naming"