Datacoins are app specific, more like ERC20 tokens on Ethereum network. The difference is that datacoins are "backed" by schema-verified data created by respective apps. So, if the data is valuable, so would be datacoins. This gives freedom to app developers to price their data in units of their app's datacoins. Now, it is possible that a category of data (say, "weather data") is available from multiple apps hosted on Storecoin and it may be impractical for a buyer to pay in individual app datacoins to access data from different apps. Such cross-app data purchases can be paid with $STORE. All datacoins are denominated in $STORE, which makes this possible. Datacoins are emitted based on the amount of data created in the tokenized apps and no two apps will create data at the same rate or volume. This separation, where data is priced in app's own datacoins instead of tying its price to base currency, allows accurate representation of the "value" of the data.