page_title: OBO Foundry
section_title: Orthogonality
hierarchical_section_title: OBO Foundry / Principles. / Orthogonality
caption_attribution_description: English: Graph depicting the OBO ID for positive chemotaxis and its Unified Resource Identifiers (URIs) in the old OBO format (before 2007) and the current version of OBO Foundry compliant URIs.
context_page_description: The Open Biological and Biomedical Ontologies Foundry is a group of people dedicated to build and maintain ontologies related to the life sciences. The OBO Foundry establishes a set of principles for ontology development for creating a suite of interoperable reference ontologies in the biomedical domain. Currently, there are more than a hundred ontologies that follow the OBO Foundry principles.
  The OBO Foundry effort makes it easier to integrate biomedical results. It does so by offering a structured reference for terms of different research fields and their interconnections.
context_section_description: Terms should be unique in the OBO space, meaning that each item has a unique ontology prefix (such as CHEBI, GO, PRO)  and a local numeric identifier within  the ontology. The choice of a numerical ID was made in order to improve maintenance and evolution of the resources. In order to participate in OBO Foundry, ontologies have to be orthogonal  and the concepts it models must be unique within OBO, so each concept has a single Universal Resource Identifier (URI). New ontologies have, then, to reuse work done in other efforts.
  Despite the ideal of uniqueness of terms and interoperability, in practice, this is difficult to enforce, leading to the occurrence of term duplication. Furthermore, some ontologies do not reuse terms or even reuse terms inappropriately.
caption: Mapping from OBO IDs to OBO Unified Resource Identifiers (URIs), unique for each item.[10]
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