Few-Shot Event Classification in Images using Knowledge Graphs for Prompting

Event classification in images plays a vital role in multimedia analysis especially with the prevalence of fake news on social media and the Web. The majority of approaches for event classification rely on large sets of labeled training data. However, image labels for fine-grained event instances (e.g., 2016 Summer Olympics) can be sparse, incorrect, ambiguous, etc. A few approaches have addressed the lack of labeled data for event classification but cover only few events. Moreover, vision-language models that allow for zero-shot and few-shot classification with prompting have not yet been extensively exploited. In this paper, we propose four different techniques to create hard prompts including knowledge graph information from Wikidata and Wikipedia as well as an ensemble approach for zero-shot event classification. We also integrate prompt learning for state-of-the-art vision-language models to address few-shot event classification. Experimental results on six benchmarks including a new dataset comprising event instances from various domains, such as politics and natural disasters, show that our proposed approaches require much fewer training images than supervised baselines and the state-of-the-art while achieving better results.