OML is a data exchange format designed to facilitate exchanging omics data around the world without forcing changes to existing databases. From an informatics perspective, OML is an XML-based data exchange format. The data exchange format (e.g., XML schema and DTD) is in scope. The structure of the systems and databases sending or receiving the information schemas are out of the scope. From a biological perspective, all kinds of omics are in scope, but the details (e.g., details of genomic sequence variations or whole genomic sequence) are out of the scope. Annotations including clinical concerns and relations with other omics concerns are in scope. The application focus is human health including clinical practice, preventive medicine, translational research, and clinical research including drug discovery. The scope includes health-associated species, including human and preclinical animals, and associated cell lines. Other species, basic research, and other scientific fields are out of scope.