Data is messy. The only thing you can do with it is preserve the original format that was used to record it, transform a copy to a format that's useful for the analysis you want to do, and join it to other, similarly messy data.
Wikipedia is a perfect example. It's messy as hell. It's blobs of data with connections between them. Most of the blobs are unstructured text (or at best semi-structured) but there are a bunch of images in various formats there, and links to outside datasources in myriad formats and locations. There are some standards and attempts to maintain order, but the whole thing is damn difficult to process by machine. It's a very, very long way from the Semantic Web.