title: Methods for storing metadata associated with individual files?
body: <p>Given a collection of files which will have associated metadata, what are the recommended methods for storing this metadata?</p>
  
  <p>Some files formats support storing metadata internally (EXIF,ID3,etc), but not all file formats support this, so what are more general options?</p>
  
  <p>Some of the metadata would almost certainly be unique (titles/descriptions/etc), whilst some would be repetitive to varying degrees (categories/tags/etc).<br>
  It may also be useful to group the metadata, if different types of attribute are required.</p>
  
  <p>Ideally, solutions should cover concepts, rather than specific language implementations.</p>