The European Bioinformatics Institute (EBI) published the Ontology Mapping Service (OXO) in 2019 as an interactive browser of mappings extracted from ontologies listed in the EBI’s Ontology Lookup Service (OLS). At the time of publication, this was limited to OBO Foundry ontologies, which mostly used imprecise oboInOwl:hasDbXref mappings.

The successor project OXO2 (homepage; GitHub; preprint) is built using the Simple Standard for Sharing Ontological Mappings (SSSOM) as a data model. It includes additional semantic mappings beyond OBO Foundry ontologies such as those listed in the Mapping Commons Registry. It additionally generates inferred semantic mappings partially based on the inference rules developed for the Semantic Mapping Assembler and Reasoner (SeMRA) that were later codified in the SSSOM specification.

OXO2 is a static resource - it doesn’t have mechanisms for adding new mappings nor reviewing existing mappings. It’s also not a user/developer-facing tool for making new inferences. It has search capability based on term label or identifier and filtering based on source/target ontology, mapping set, or predicate type. It displays mappings in a tabular way, but does not have graph-based visualization nor exploration.

OXO2 is primarily maintained by Henriette Harmse with nearly all recent commits assisted by Anthropic’s Claude.