Towards More Reliable Web Metadata: Do Register Classifiers Learn Register or Genre Features?

Antti Kanner, Tuomas Lundberg, Erik Henriksson, Veronika Laippala


Abstract
Transformer-based web register classifiers are widely used to provide metadata for web crawls and to focus web-data sampling on specific register classes, such as news articles or advertisements. However, it remains unclear what these classifiers actually learn: do they detect pervasive linguistic features characteristic of registers, or do they rely on structural cues more indicative of genre? We examine this question through two hypotheses: the text-macrostructure hypothesis proposes that classifiers rely on structural features more typical of genres, whereas the feature-density hypothesis predicts that they identify typically register-associated features. Using English, Finnish, and French data from HPLT 3.0, we segment documents into thirds and compare classifier predictions for full documents and segments through five complementary analyses: main-label agreement, cosine similarity, confusion profiles, SACX keyword-weight correlations, and SACX keyword stability. As a more direct control, we compare predictions for a sample of untruncated documents with predictions for the same documents after their sentence order has been randomised. Top-label assignments and prediction vectors remain highly similar after shuffling, although the positional gradients are attenuated, indicating that sentence order contributes to classifier behaviour without determining its broader prediction profile. Overall, the results are more consistent with the feature-density hypothesis, although both hypotheses retain explanatory value.
Anthology ID:
2026.wac-1.14
Volume:
Proceedings of the 13th Web-as-Corpus Workshop
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Pedro Ortiz Suarez, Laurie Burchell, Nikola Ljubešić, Yves Scherrer, Veronika Laippala, Vuk Dinić, Thom Vaughan
Venues:
WAC | WS
SIG:
SIGWAC
Publisher:
Association for Computational Linguistics
Note:
Pages:
147–160
Language:
URL:
https://aclanthology.org/2026.wac-1.14/
DOI:
Bibkey:
Cite (ACL):
Antti Kanner, Tuomas Lundberg, Erik Henriksson, and Veronika Laippala. 2026. Towards More Reliable Web Metadata: Do Register Classifiers Learn Register or Genre Features?. In Proceedings of the 13th Web-as-Corpus Workshop, pages 147–160, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Towards More Reliable Web Metadata: Do Register Classifiers Learn Register or Genre Features? (Kanner et al., WAC 2026)
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PDF:
https://aclanthology.org/2026.wac-1.14.pdf