Quads forming a semantic web
A semantic web consists of quads
ID: Subject → Predicate → Object.
Selections of quads forming facets
A facet represents a specific way of looking at an information universe in order to be useful for fulfilling a certain task.
A facet represents a specific section of a semantic web. A "section" is therefore a specific selection of quads.
How do we specify such a selection of quads? Answer: by specifying some parts of the quads, that is
- the quads' subject: any or some specific by specifying them explicitly or implicitly
- the quads' predicate: any or some specific by specifying them explicitly or implicitly
- the quads' object: any or some specific by specifying them explicitly or implicitly
Example: NASA's use of SMW
For example NASA uses many Semantic MediaWikis, that's why we can say that one field of application for SMW is NASA. So we are interested in the question how does NASA use SMW? One way of answering this question is to explain the ontology that NASA uses on some of its SMWs. Let's call this Ontology "Field of Application NASA".
Next question is: what consitutes Ontology "Field of Application NASA"?
As mentioned above, we ask which quad patterns constitute Ontology "Field of Application NASA"? Here's the answer:
|Anything||Belongs to field of application||Any value(s)|
That reads like this: any quad that fulfills the following pattern:
- the subject can be any page
- the predicate must be the property Belongs to field of application
- the object must be Component 607119
Which quads are these? Here's the answer:
We can visualize this:
<mermaid2 profile="Component 160431" abstraction="instinst"/>
More importantly we can let SMW prescind these facts onto their type level:
<mermaid2 profile="Component 160431" abstraction="typetype"/>
Assigning and retrieving properties
For example, we want to know all occurrences at which a property is involved in any way throughout a SMW. Conceptually SMW makes use of properties in these ways:
|Assign a property value
Retrieve a property value in #ask and #show queries by