Fortunately, the retailer and the manufacturer can agree that both belong to the class of Workstations/Desktops. We also find out to what extent a Prof Desktop has the required memory, CPU and so forth for a PC for Gamers. One of the rules for this is shown in Figure 2.

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

 Figure 2. A Rule for Semantic Resolution The rule says that, if the two premises above the line are true, then so is the conclusion. In the rule, "some-item1", "that-class" and so on are place holders, or variables, that will be filled in with actual values, such as "PC for Gamers" and "Computers" when the rule is run. Apart from the place holders, the rest of the words in the rule are in open vocabulary, open syntax, English. So, the rule defines the meaning of the last sentence in terms of the meanings of the first two. To avoid infinite regress, this process stops at the headings of data tables. The headings are similar sentences, and the number of place holders in a heading is the number of columns in the table. To view and run the example, one can point a browser to (Reeng 2006) and select SemanticResolution1.

## An Rdf Query Example

The paper (Haase et al 2004) describes a use case in which 14 test questions are put to some RDF data about published papers and their authors. The paper describes several Semantic Web query languages, and shows that none of those languages can answer all 14 questions. It is straightforward to write rules that allow the system to answer all 14 questions. One such rule is shown in Figure 3.

![0_image_1.png](0_image_1.png)

3