A problem which facebook doesn’t need to deal with which we will is changing photos after they have been tagged. This is because on facebook once a photo is uploaded it can not be changed. If a user wants to replace it they delete it (along with all comments and tags) and upload a new one.
With our system simply hotlinking to the images rather than hosting them ourselves, it means we have no control over ensuring that the image is not changed or removed.
To help with this we will take a hash of the image the first time it is seen and then compare this to the image periodically (more often for images which are viewed more often). If an image is changed the old tags can be archived and removed from the live image.
These archived tags could then be presented to the site owner who can re-add them to the new image if appropriate.
If an image is removed and this is detected then it can be removed from people’s albums so that it does not link to dead images.
Pingback: Week 4 | Tag4Fun