[UPDATE 07/01/2019] I have changed the operator in the trait expressions. Thanks Glenn!
Initially, when we think of segments (or clusters) for ad segmentation, we think of ever-growing groups of cookies. Simple use case like purchasers, visitors to our website, subscribers to a newsletter or owners of a device fit in this model. However, advanced (and not so advanced) use cases do not work well with this model, where we have visitors entering and leaving regularly a segment, so a segment can shrink in size:
- Retargeting dropped baskets: the moment someone places an order, you do not want to retarget him again
- Customers of a mobile operator: it is very common nowadays to switch to a different provider frequently
- Age group: ever day, visitors enter one particular age group or leave it, as people grow older