A delta dataset is a dataset that contains information on the inheritance and difference of a Child dataset as compared to a Parent dataset. This data structure is used primarily in LCA databases to manage variations of similar activities efficiently whilst avoiding data redundancy.
The concept originates from the ecoinvent database architecture, where it serves as a mechanism for data inheritance and variation management. Rather than storing complete, independent datasets for every variation of an activity, the delta dataset approach allows practitioners to define a reference (parent) dataset and then specify only the differences (deltas) needed to create related variants.
In practice, when a child dataset is needed, it is constructed by combining the parent dataset with the delta dataset. The parent dataset provides the baseline data, whilst the delta dataset specifies which field values should be modified, added, or removed to create the child dataset. This inheritance structure means that field values are passed from the parent to the child except where explicitly overridden by the delta dataset.
This approach offers several advantages for LCA database management. It significantly reduces data storage requirements and maintenance burden, as common information needs to be maintained in only one location. When updates are needed to shared characteristics, they can be made once in the parent dataset and automatically propagate to all child datasets that inherit those values. This ensures consistency across related datasets whilst still allowing for necessary variations in geography, technology level, temporal validity, or other distinguishing characteristics.
For example, a parent dataset might represent the global average production of a material, whilst delta datasets define the specific differences for production in individual countries or regions. Each delta would specify only those exchanges, parameters, or properties that differ from the global average, such as electricity grid mix, transport distances, or regulatory requirements.
