The Biological Expression Language (BEL) is a language for representing scientific findings in the life sciences in a computable form.

BEL is a language for representing scientific findings in the life sciences in a computable form. BEL is designed to represent scientific findings by capturing causal and correlative relationships in context, where context can include information about the biological and experimental system in which the relationships were observed, the supporting publications cited and the process of curation.

BEL is intended as a knowledge capture and interchange medium, supporting the operation of systems that integrate knowledge derived from independent efforts. The language is designed to be use-neutral, facilitating the storage and use of structured knowledge for inference by applications through a knowledge assembly process that can create computable biological networks. While BEL does not prescribe any particular assembly process or any particular knowledge format for the output of an assembly process, a suite of software components called the BEL Framework provides everything necessary to create, compile, assemble, and deliver computable knowledge models to BEL-aware applications.

The current version of BEL provides the means to describe biological interactions qualitatively but not to quantify the magnitude or rate of these interactions. This limitation is by design because this quantitative information has significant variability and is not consistently reported in the literature. It is our hope that future versions of BEL can accommodate these additional data, and that YOU are able to work together with the OpenBEL Consortium to make this happen.

Knowledge in BEL is expressed as BEL Statements that are stored in BEL Documents. BEL Documents are structured text documents that contain BEL Statements, along with sufficient additional information to fully describe and process the document.

BEL Statements are generally defined as a semantic triple composed of a subject - predicate - object where the subject is always a BEL Term and the object can be either another BEL Term or a BEL Statement. The predicate is one of the BEL Relationship types describing the relationship between the subject BEL Term and the object.


BEL Terms are composed of BEL Functions and entity definitions referenced using BEL Namespace identifiers. Each BEL Term represents either an abundance of a biological entity, the abundance of human AKT1 for example, or a biological process such as cardiomyopathy.
Each BEL Statement can optionally be annotated with one or more references which express additional information about the statement itself such as the tissue, species, and cell line for example. Within a BEL Document statements can be associated with a set of Annotation Types that tag each statement and that can be used to describe the context in which the statement was observed and increases the richness of the knowledge being captured.

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