Whether something is in the realm of metadata management versus taxonomy management depends on the following factors
If you work in information architecture or usability, you have considered core organizing principles as they apply to web applications. In fact, when many people think of taxonomy, they are considering navigational constructs – the hierarchy of site information. So you have no doubt considered a taxonomy from this perspective – a site map, site hierarchy or navigational taxonomy. This is a valid perspective. We have lots of projects where we develop or test or review navigational constructs and apply various heuristics to evaluating how well they work – whether or not the categories are balanced, if they use consistent grouping principles, whether the labels are descriptive and so on.