How to group all level-2 label, without adding a value for each level-1 label ?

[quang-anh-nguyen]

Hello, I am working with hierarchical multi-label classification, with many levels of labels. Here is my label config, assuming that the first level labels are A and B, while the second level labels are A1, A2 and B1, B2, B3.

<View>
  <Text name="text" value="$text"/>
  <View style="box-shadow: 2px 2px 5px #999;
               padding: 20px; margin-top: 2em;
               border-radius: 5px;">
    <Header value="Choose themes present in the text"/>
    <Choices name="theme" toName="text"
             choice="multiple" showInLine="true">
      <Choice value="A"/>
      <Choice value="B"/>
    </Choices>

    <!-- Sub-themes for ESG -->
    <View visibleWhen="choice-selected"
          whenTagName="theme"
          whenChoiceValue="A">
      <Header value="Select sub-themes for A"/>
      <Choices name="A_subtheme" toName="text"
               choice="multiple" showInLine="true">
        <Choice value="A1"/>
        <Choice value="A2"/>
      </Choices>
    </View>

    <!-- Sub-themes for Conformité -->
    <View visibleWhen="choice-selected"
          whenTagName="theme"
          whenChoiceValue="B">
      <Header value="Select sub-themes for B"/>
      <Choices name="B_subtheme" toName="text"
               choice="multiple" showInLine="true">
        <Choice value="B1"/>
        <Choice value="B2"/>
        <Choice value="B3"/>
      </Choices>
    </View>

  </View>
</View>


<!-- {
  "data": {"text": "This is a great 3D movie that delivers everything almost right in your face."}
} -->

And this is an output example with correct labels as A2, B3

[
    {
        "value": {
            "choices": [
                "A",
                "B"
            ]
        },
        "id": "8bcyK27T0I",
        "from_name": "theme",
        "to_name": "text",
        "type": "choices"
    },
    {
        "value": {
            "choices": [
                "B3"
            ]
        },
        "id": "05s0gu-RXH",
        "from_name": "B_subtheme",
        "to_name": "text",
        "type": "choices"
    },
    {
        "value": {
            "choices": [
                "A2"
            ]
        },
        "id": "R3cFXz42dB",
        "from_name": "A_subtheme",
        "to_name": "text",
        "type": "choices"
    }
]

As seen, it includes the second level labels in two different fields named A_subtheme and B_subtheme. My question is if it is possible to configure to merge all the sub-label into a same field, and its value may be either [A2, B3] or a dict {A: A2, B: B3} of some sorts. This will make the process more systematic, instead of having to create a new name for every first-level labels.

If I give them the same name, say subtheme, an error is raised: Label config contains non-unique names

If you have any answers, please let me know. Thank you very much.

[heidi-humansignal]

Hello,

Thank you for contacting Label Studio,

Label Studio doesn’t currently provide a straightforward way to merge all sub-labels into a single field when using separate <View visibleWhen="choice-selected"> sections. In other words, if you rely on conditions to display sub-labels (e.g. <View ... whenChoiceValue="A"> and <View ... whenChoiceValue="B">), you’ll inevitably end up with separate from_name fields for each group of sub-labels.
Below are two approaches to unify your hierarchical labeling into one output field instead of separate “A_subtheme” and “B_subtheme” fields:

---

1) Use the <Taxonomy> Tag
A single <Taxonomy> configuration can capture both top-level and sub-level labels in one field:

<View> <Text name="text" value="$text"/> <Taxonomy name="themes" toName="text" leafsOnly="true" maxUsages="10"> <Choice value="A"> <Choice value="A1"/> <Choice value="A2"/> </Choice> <Choice value="B"> <Choice value="B1"/> <Choice value="B2"/> <Choice value="B3"/> </Choice> </Taxonomy></View>

• How it works: Annotators see a hierarchical tree. If they select A, then they can further pick A1, A2, etc. Because leafsOnly="true", Label Studio only records the final label(s) chosen.
• Output: All chosen labels (top-level and sub-level) appear in the single "themes" field, simplifying how you parse the results.

---

2) Nest All Labels Under One <Choices> Tag with allowNested="true"
If you want to stay with <Choices> (rather than <Taxonomy>), you can nest sub-labels under one from_name:

<View> <Text name="text" value="$text"/> <Choices name="themes" toName="text" choice="multiple" showInline="true" allowNested="true"> <Choice value="A"> <Choice value="A1"/> <Choice value="A2"/> </Choice> <Choice value="B"> <Choice value="B1"/> <Choice value="B2"/> <Choice value="B3"/> </Choice> </Choices></View>

• How it works: All top-level and sub-level labels are grouped in one “themes” control. If an annotator clicks a top-level label, it can expand to show sub-labels.
• Output: You get a single "themes" entry in your annotation results, typically in a nested list structure. The sub-label(s) selected under each top-level label appear together.
  That said, the nested <Choices> approach behaves a bit differently than visibleWhen logic. For example, sub-labels remain visible once you expand them in the interface. If your team prefers a more typical “expand>pick>collapse” workflow, <Taxonomy> is often more intuitive.

---

Which Should You Pick?

• Use <Taxonomy> if you want a clean hierarchical selection that unifies everything into one control and one output array. It was built for hierarchical label structures.
• Use nested <Choices allowNested="true"> if you need to remain within the <Choices> tag for some reason (e.g., you prefer the user interface it offers). Just keep in mind it yields a nested array structure in your annotations.
  At the moment, there isn’t a built-in trick to keep your separate conditional <View ... whenChoiceValue="A"> blocks while forcing everything into one single output name — each set of <Choices> must have its own unique from_name. But the two approaches above can solve this by collecting everything under one control.
  I
  hope this clarifies how to unify your multiple levels of labels into a single field. Please let me know how it goes or if you have any questions!
  Best regards,

Comment by Oussama Assili
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