Historical language models play a crucial role in the study of languages, and can benefit tasks such as named-entity recognition (NER), part-of-speech (PoS) tagging, and post-OCR correction, among others. Despite their relevance, most efforts have been concentrated on English. To the best of our knowledge, no such model exists for historical Portuguese. In this work, we introduce PortOldBERT, the first historical Portuguese encoder language model. We demonstrate its usefulness by comparing PortOldBERT’s performance with Albertina, the encoder on which it is based, across multiple tasks—pseudo-perplexity, NER, PoS tagging, word error rate (WER) prediction, and OCR error detection—and for different historical periods. PortOldBERT consistently outperforms Albertina in historical data, demonstrating its ability to effectively integrate historical linguistic contexts while retaining the ability to process contemporary text.

To foster the neural encoding of Portuguese, this paper contributes foundation encoder models that represent an expansion of the still very scarce ecosystem of large language models specifically developed for this language that are fully open, in the sense that they are open source and openly distributed for free under an open license for any purpose, thus including research and commercial usages. Like most languages other than English, Portuguese is low-resourced in terms of these foundational language resources, there being the inaugural 900 million parameter Albertina and 335 million Bertimbau. Taking this couple of models as an inaugural set, we present the extension of the ecosystem of state-of-the-art open encoders for Portuguese with a larger, top performance-driven model with 1.5 billion parameters, and a smaller, efficiency-driven model with 100 million parameters. While achieving this primary goal, further results that are relevant for this ecosystem were obtained as well, namely new datasets for Portuguese based on the SuperGLUE benchmark, which we also distribute openly.