RT Journal Article SR Electronic T1 In this issue: Ontologies a key concept in informatics and key for open definition of cases, exposures and outcome measures JF BMJ Health & Care Informatics FD BMJ Publishing Group Ltd SP i OP v DO 10.14236/jhi.v22i2.170 VO 22 IS 2 A1 de Lusignan, Simon YR 2015 UL http://informatics.bmj.com/content/22/2/i.abstract