  In this paper, we present InferES - an original corpus for Natural Language
Inference (NLI) in European Spanish. We propose, implement, and analyze a
variety of corpus-creating strategies utilizing expert linguists and crowd
workers. The objectives behind InferES are to provide high-quality data, and,
at the same time to facilitate the systematic evaluation of automated systems.
Specifically, we focus on measuring and improving the performance of machine
learning systems on negation-based adversarial examples and their ability to
generalize across out-of-distribution topics.
  We train two transformer models on InferES (8,055 gold examples) in a variety
of scenarios. Our best model obtains 72.8% accuracy, leaving a lot of room for
improvement. The "hypothesis-only" baseline performs only 2%-5% higher than
majority, indicating much fewer annotation artifacts than prior work. We find
that models trained on InferES generalize very well across topics (both in- and
out-of-distribution) and perform moderately well on negation-based adversarial
examples.
