Take context from the input text and decide on the accurate relationship between 'MIUI' and 'Xiaomi' from the options provided.
Options: operator, owned by, developer, location of formation

Xiaomi has refined MIUI over the past year to create MIUI 7, which has a colourful interface with better performance, battery-saving optimisations and an even wider variety of personalisation options,” Xiaomi said in a statement.
developer