Maximizing the personal, public, research, and clinical value of genomic information will require that clinicians, researchers, and testing laboratories exchange genetic variation data reliably. The Variation Representation Specification (VRS, pronounced "verse") — written by a partnership among national information resource providers, major public initiatives, and diagnostic testing laboratories — is an open specification to standardize the exchange of variation data.
Here we document the primary contributions of this specification for variation representation:
- Terminology and information model. Definitions for biological terms may be abstract or intentionally ambiguous, often accurately reflecting scientific uncertainty or understanding at the time. Abstract and ambiguous terms are not readily translatable into a representation of knowledge. Therefore, the specification begins with precise computational definitions for biological concepts that are essential to representing sequence variation. The VRS information model specifies how the computational definitions are to be represented in fields, semantics, objects, and object relationships.
- Machine readable schema. To be useful for information exchange, the information model should be realized in a schema definition language. The VRS schema is currently implemented using JSON Schema, however it is intended to support translations to other schema systems (e.g. XML, OpenAPI, and GraphQL). The schema repository includes language-agnostic tests for ensuring schema compliance in downstream implementations.
- Conventions that promote reliable data sharing. VRS recommends conventions regarding the use of the schema and that facilitate data sharing. For example, VRS recommends using fully justified allele normalization using an algorithm extending NCBI's SPDI model.
- Globally unique computed identifiers. This specification also recommends a specific algorithm for constructing distributed and globally-unique identifiers for molecular variation. Importantly, this algorithm enables data providers and consumers to computationally generate consistent, globally unique identifiers for variation without a central authority.
- A Python implementation. We provide a Python package (vrs-python) that demonstrates the above schema and algorithms, and supports translation of existing variant representation schemes into VRS for use in genomic data sharing. It may be used as the basis for development in Python, but it is not required in order to use VRS.
The machine readable schema definitions and example code are available online at the VRS repository (https://github.com/ga4gh/vrs).
Readers may wish to view a :ref:`complete example <example>` before reading the specification.
For a discussion of VRS with respect to existing standards, such as HGVS, SPDI, and VCF, see :ref:`relationships`.