Precisely, there is only an imaginary Novena "boundary".
To attract the gullible and newbies in property (of which I see many here clamouring for a "Novena' location) tsk tsk... some cunning developers opt to use the name "Novena" in their project name, even if their project is squarely centred in D12.
Therefore, the names containing Novena are of no use. Better to use the road names themselves. Therefore, I disagree that some parts of Novena are in D12. It is like some eatery after uprooting themselves in D15 and planting themselves into a suburb like Choa Chu Kang, and still callinh themselves Katong Laksa. So does it mean that some parts of Katong are in Choa Chu Kang?
Get real my friends