  We introduce the "Incremental Implicitly-Refined Classi-fication (IIRC)"
setup, an extension to the class incremental learning setup where the incoming
batches of classes have two granularity levels. i.e., each sample could have a
high-level (coarse) label like "bear" and a low-level (fine) label like "polar
bear". Only one label is provided at a time, and the model has to figure out
the other label if it has already learnfed it. This setup is more aligned with
real-life scenarios, where a learner usually interacts with the same family of
entities multiple times, discovers more granularity about them, while still
trying not to forget previous knowledge. Moreover, this setup enables
evaluating models for some important lifelong learning challenges that cannot
be easily addressed under the existing setups. These challenges can be
motivated by the example "if a model was trained on the class bear in one task
and on polar bear in another task, will it forget the concept of bear, will it
rightfully infer that a polar bear is still a bear? and will it wrongfully
associate the label of polar bear to other breeds of bear?". We develop a
standardized benchmark that enables evaluating models on the IIRC setup. We
evaluate several state-of-the-art lifelong learning algorithms and highlight
their strengths and limitations. For example, distillation-based methods
perform relatively well but are prone to incorrectly predicting too many labels
per image. We hope that the proposed setup, along with the benchmark, would
provide a meaningful problem setting to the practitioners

Computer Vision and Pattern Recognition;Artificial Intelligence;Machine Learning