<lanl:marko, lanl:worksWith, lanl:jhw> <lanl:marko, lanl:hasBodyPart, lanl:markos_arm>
These triples are diagrammed in Figure 1. The union of all RDF triples is the Semantic Web.

![0_image_0.png](0_image_0.png)

The benefit of RDF, and perhaps what is not generally appreciated, is that with RDF it is possible to represent anything in relation to anything by any type of qualified relationship. In many cases, this generality can lead to an uncontrolled soup of relationships; however, thanks to ontology languages such as RDFS and OWL, it is possible to formally constrain the topological features of an RDF network and thus, subsets of the larger Semantic Web.

## 3 The Rdf Schema And Web Ontology Language

The Resource Description Framework and Schema (RDFS) [4] and the Web Ontology Language (OWL) [6] are both RDF languages used to abstractly define resources in an RDF network. RDFS is simpler than OWL and is useful for creating class hierarchies and for specifying how instances of those classes can relate to one another. It provides three important constructs: rdfs:domain, rdfs:range, and rdfs:subClassOf2.

While other constructs exist, these three tend to be the most frequently used when developing an RDFS ontology. Figure 2 provides an example of how these constructs are used. With RDFS (and OWL), there is a sharp distinction between the ontological- and instance-level of an RDF
network. The ontological-level defines abstract classes (e.g. lanl:Human)
and how they are related to one another. The instance-level is tied to the ontological-level using the rdf:type predicate3. For example, any lanl:Human can be the rdfs:domain (subject) of a lanl:worksFor triple that has a lanl:Institution as its rdfs:range (object). Note that the lanl:Laboratory is an rdfs:subClassOf a lanl:Institution. According to the property of subsumption in RDFS reasoning, subclasses inherit their parent class restrictions. Thus, lanl:marko can have a lanl:worksFor relationship with lanl:LANL. Note that RDFS is not intended to constrain relationships, but instead to infer new relationships based on restrictions. For instance, if lanl:marko lanl:worksFor some 2rdfs is a prefix for http://www.w3.org/2000/01/rdf-schema\# 3rdf is a prefix for http://www.w3.org/1999/02/22-rdf-syntax-ns\#