The term data partner can have two meanings in digital marketing context.
Data partner can refers to site publishers who pass through and sell data to ad networks and data vendors. Information is collected on publishers’ sites and passed through by using third party tags or cookie matching process.
How Chango, a search retargeting company, collects search keyword data from data partners:
A data buying offer by eXelate to publishers:
From an other point of view, the data partner can be a dedicated data vendor who sells data to ad networks and ad exchanges for valuing inventory or directly to merchant websites for personalizing and conversion purposes. The data sold by data partners (aka data vendors) can be online data or offline data.
Thus eXelate has data partners which collec data for it, but eXelate is also a data partner or vendor from an ad exchange point of view.