Roughly speaking, membership of a category means "Berlin is a City". In Semantic MediaWiki's RDF export, this is explicit: the article has an rdf:type relationship to its category.
Note that an alternate wiki convention is to use plural names for classes of things, thus Category:Cities, and use singular names for topics.
Below is an sample inline query for cities:
| Name | Population | Has area | Average rainy days |
|---|---|---|---|
| Demo:London | 7,825,200 | 1,706.80 km²659.00 sqmi <br /> | 145 |
| Demo:Berlin | 3,520,061 | 891.85 km²344.34 sqmi <br /> | 106.3 |
| Rome | 2,761,477 | 1,285.31 km²496.26 sqmi <br /> | 84.5 |
| Demo:Paris | 2,234,105 | 105.40 km²40.69 sqmi <br /> | 111.5 |
| Warsaw | 1,720,398 | 516.90 km²199.58 sqmi <br /> | 159 |
| Demo:Munich | 1,353,186 | 310.43 km²119.86 sqmi <br /> | 129.4 |
| Demo:Cologne | 1,080,394 | 405.02 km²156.38 sqmi <br /> | 132.5 |
| Demo:Frankfurt | 679,664 | 248.31 km²95.87 sqmi <br /> | 108.9 |
| Demo:Stuttgart | 606,588 | 207.35 km²80.06 sqmi <br /> | 112.4 |
| Demo:Würzburg | 126,635 | 87.63 km²33.83 sqmi <br /> | 156 |