In a grouped list, how to display items of an intersection of two groups

Question

Provided I have a category which gives x non mutually exclusive options. I have a list of items which can be tagged with several of these mutually non exclusive options.

• Item 1
  • Group A
• Item 2
  • Group B
• Item 3
  • Group A + B
• Group C ...

A user can now select one/several of the options so they retrieve a list of items according to each options they selected and the union of these options, if needed.

• Group A -- selected
• Group B -- selected
• Group C

I have a constraint when it comes to displaying the result: the items must be grouped under the options they are tagged with.

• Group A
  • Relevant items
• Group B
  • Relevant items

This is where I am faced with a choice to make in order to display the items which are tagged with several of the select options - hence are at the intersection of several groups.

The alternatives are: display each items several times, one under each group they belong to, like so:

• Group A
  • Item 1
  • Item 3
• Group B
  • Item 2
  • Item 3

Or display a group for each intersection of groups

• Group A
  • Item 1
• Group B
  • Item 2
• Group A + B
  • Item 3

Solution 1 result in a duplication of the content (the item), solution 2, a duplication of the meta-information (the categories).

Now, this was an imaginary explanation. My real case implies 5 categories each with between 3-5 options and two nested grouping based on 2 of these categories. As a result, whichever solution comes with a big overload of duplicated information - just think of the possible combination of groups. Nonetheless, I would like to have your opinions and knowledge on which would be the worse of two evils out of these two solutions ?

I might add that the value proposition I am working with for this content is partly, the number of items of content. Hence, albeit being more readable, I believe that solution 1 could be perceived as bearing disingenuity as it increase that number. Solution 2 would be worse in terms of readability though.

Of course, I am also investigating alternatives to grouping altogether but would like to put this problem out there for reflexion and see if someone comes with different angles than mine.

Answer 1

There is really no 'worse' option unless you are quite familiar with the type of data that is going to be displayed most frequently, because it will be the scenario in which there is more duplication of information than the other. As you mentioned already, whichever solution comes with a big overload of duplicated information, so you should actually focus on how to optimize the end goal for the user.

We don't have any context on what the actual items represent, but because it is a grouped list that is quite complex in its potential structure, the optimum solution will be one in which you give some flexibility to the user to customize the end result.

At the top level, you can allow the result to be displayed by the number of options listed from highest to lowest number of options (and then sort by the options alphabetically and then the categories alphabetically for example) OR allow the results to be displayed by the categories, and then the number of options.

Then you can layer onto the features the ability to filter the returned results by the categories and the options, so that it is clear to the user whether they are viewing the entire search result or a subset.