I think this is so important. How data is stored should never be dependent on how it appears - appearance should only ever be an interpretation of data. Simplest example is a clock (data), which can be visualised as either analog hands on a dial, or a digital display.
Can I dare to bring the subject of whether a “dictionary” of keywords is a good idea or not?
In my app, all keywords can exist as standalone, hierarchies are simply one or more organisations of those keywords. This allows any keyword to be integrated into multiple hierarchies if necessary, or to be used on their own.
My app provides a two column browser, which allows dragging and dropping from the global list to the hierarchy view. This avoids the horror of PL5’s minute hierarchy display, where you have to drag a word to try and find the parent you want to attach it to, with the scrolling going crazy when you touch either the top or bottom boundary.
The “dictionary window” also separates organisation from assignment, in that keywords can be verified for spelling instead of hoping you have spelt them correctly whilst typing new keywords into the keywords entry field.
In my app, the rules allow for the direct entry of new keywords whilst assigning to an image, but such new words are initially only assigned as standalone. This allows for later organisation of such words into one or more hierarchies without losing the immediacy of being able to search for that single keyword.
Of course, once keywords have been assigned to images, if they are then added to new hierarchies, the user would need to search for images that contain the standalone keyword and replace it with its hierarchical counterpart. Once more, this provides a safe way of ensuring the correct hierarchy has been applied.
Using a managed dictionary also means that we are not reliant on PL5 scanning folders on disk to build up the list of already available hierarchies, with the chance that certain unvisited folders will not be scanned and some hierarchies not included.
Once we have our managed dictionary, entering hierarchical keywords is no longer prone to memory lapses and incorrect assignment that can happen when typing a separated list of keywords in the hope that something, somewhere can organise them correctly.
It would also pave the way for the possibility of importing pre-defined lists and hierarchies but, more importantly, it takes out the “multi-purpose” add/edit/compose nature of the tiny little palette we presently have, where it is difficult to know whether you are deleting a word from an image or the entire list of hierarchies.
Deleting a keyword in the token field of my app is only ever about removing it from the selected image(s). In order to remove it from the dictionary, or change the spelling, you need to go to the manager window where, deleting or editing a keyword will automatically update every image to which it has ever been applied.
Does this help or further confuse?