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BERT Classification Learner

Trains a text classification model on top of the provided BERT model. The model is extended with 3 layers:

GlobalAveragePooling1D layer
Dropout layer
Dense layer

Besides the typical classification task where every row is assigned a single class it is also possible to train a model for multi-label classification where a row can be assigned multiple labels.

If a validation table is provided, then the model performance is evaluated on that data after every epoch.

Options

Settings

Sentence column: A column with plain text (String) or Documents, that contains text to be classified. No special pre-processing is needed.
Class column: A column that contains class labels.
Max sequence length: The maximum length of a sequence after tokenization. The upper limit is 512.
Multi-label classification: Enables multi-label classification mode. In this mode multiple labels (classes) can be assigned to each text.
Class separator: The character used to separate different classes assigned to a given text in multi-label classification mode.

Advanced

Number of epochs: The number of epochs used for training the classifier.
Batch size: The size of a chunk of the input data used for model update.
Validation batch size: The size of a chunk of the validation data to process.
Fine tune BERT: If checked then the weights of the BERT model will be trained along with the additional classifier. Fine-tuning BERT will be more resource and time intensive, but the results are usually better.
Optimizer: Available optimizers and their configuration.

Python

Python

Select one of the Python execution environment options:

use default Python environment for the Redfield BERT Nodes (can be configured on the preference page)
use Conda environment from a Conda flow variable (only selectable if such a flow variable is available)

Input Ports

: BERT Model
: Data Table
: Optional Validation Table

Output Ports

: BERT Classifier model
: Statistics of the training process

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Installation

To use this node in KNIME, install the extension Redfield BERT Nodes from the below update site following our NodePit Product and Node Installation Guide:

v5.7

Plugin provider: Redfield AB

Plugin version: 1.0.3.202506120120

On NodePit since: 2025-09-12

Last update: 2026-01-08

KNIME versions: v5.8, v5.7, v5.6, v5.5, v5.4, v5.3, v5.2, v5.1, v4.7, v4.6, v4.5, v4.4, v4.3, v4.2

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