Basic data field in Rossum extraction schema can be used to extract a single value, e.g. extraction of Invoice Number. However, in some cases you might need to extract multiple values under one field. For such cases, Rossum schema supports also extraction of data fields with multiple values – multivalue fields.

What is a multivalue field

A simple multivalue field is a special type of datapoint which represents a container for data with multiple occurrences. It is useful in cases like documents containing multiple PO numbers or multiple Container or Seal Numbers. Using a multivalue field for extraction of such data will allow you to have all these values extracted under the same field ID.

Creating a sample multivalue field

For purposes of this article, let’s say your documents have multiple PO numbers and you need to extract them all. We will create a new multivalue field called “PO number”.

The attributes of the field required for creating our “PO Number” multivalue field in the extraction schema would be as follows:

 {
        "category": "multivalue",
        "id": "po_number_multi",
        "label": "PO Number",
        "children": {
          "rir_field_names": ["order_id"],
          "category": "datapoint",
          "id": "po_number",
          "label": "PO Number",
          "type": "string" }
}

Regardless of the amount of PO Numbers on the document, there will be only one PO Number in the "children" attribute of the multivalue field. Moreover, the multivalue field will be initialized by the AI Engine output “order_id”. You can explore the multivalue field and its attributes in more detail in our API documentation.

Adding a new multivalue field to schema

The process of creating a multivalue field is the same as adding a new custom data field. In the Rossum schema editor, navigate to the section where you would like to add this new multivalue field. Copy the necessary data for this new field and paste it to the "children" attribute of that selected section. You will see the newly created multivalue field in the left sidebar.

Capturing multivalue field

On the validation screen in Rossum UI, the simple multivalue field looks similar to the regular data field. But on the right side, instead of actual values, you can see a number reflecting how many values were extracted. After clicking on it, the multivalue field expands and you can see all the extracted values.

For adding a new value, just click the “+ Add a value” button and use a Bounding box to capture this field on the document. You can also use some available keyboard shortcuts to speed up the data capture.

Simple multivalue field in the exported data

How will the exported data look like if you have a simple multivalue field in your extraction schema? In the spreadsheet, the multivalue field will populate 1 row per each value it contains. Other header field values will be repeated for each row for the same document.

In the example above, there is one multivalue field with 3 PO Number values. In the exported data, this will result in 3 lines. For each line, there will be a different PO Number and all the other columns (header field values) will be repeated.