Alice selects the "Action" genre from the filter select dropdown on the front page.
Alice is shown a list of stories where the first page is tagged with the "Action" tag.
Alice clicks on the link to the first story.
Alice clicks on the first option.
The option leads to two possible versions: one has the "Action" tag and the other does not.
The version selection algorithm currently ignores the tags and offers a version to Alice that might not have the "Action" tag.
The version selection algorithm should be modified, so that if a user's traversal of the story tree has a filter applied to it, the version selection algorithm only serves pages which definitely have the filtered tag. This will mean that the user will only be shown versions with that tag on it.
If a user clicks on an option and there is no version with the required tags, but there are pages without the required tags, present an error message saying "There is no page here with tag X, but there are versions which do not have tag X. You can remove your filter and read one of those versions, or write a new page here with your current tag."
The version selection algorithm should be modified, so that if a user's traversal of the story tree has a filter applied to it, the version selection algorithm only serves pages which definitely have the filtered tag. This will mean that the user will only be shown versions with that tag on it.
If a user clicks on an option and there is no version with the required tags, but there are pages without the required tags, present an error message saying "There is no page here with tag X, but there are versions which do not have tag X. You can remove your filter and read one of those versions, or write a new page here with your current tag."