## 5 Assessment
### Feature Discussion  
As this initial investigation demonstrated that the REFINERY Platform provides comprehensive solutions for all protection goals regarding data security and privacy, we now assess to what extent the ten data characteristics, which we have identified and discussed in Section 2, are addressed in our approach. The fact that data are not consumed during processing, i.e., the data volume grows continuously (Characteristic I), is addressed by the deployment of a distributed file system, namely HDFS, for the management of raw data. Since HDFS distributes the data across a multitude of nodes, it is suitable for the efficient handling of big data. In addition to the raw data, the number of data products to be managed in the REFINERY Platform is also growing steadily. With the introduction of Virtual Use Case Zones, i.e., a way to store data products only temporarily in volatile storages, data products that are tailored to rather uncommon use cases and therefore rarely in demand are automatically removed after usage. However, the knowledge gained during production is not lost, since the processing steps required to manufacture these data products are still available in the ontology. That is, if required, the data products can be restored from the raw data at any time. Since data can be losslessly duplicated, which inevitably leads to a loss of value (Characteristic II), data consumers are not given direct access to the raw data or the processable information retrieved from them. Only the data products can be accessed by data consumers via restricted interfaces. This preserves the value of the raw data. The REFINERY Platform does not provide any special protection against the duplication of data products after they have been delivered to data consumers. However, this is not necessary from our point of view, as it is in the interest of data consumers that the value of the data products acquired by them is not diminished, e.g., by means of unregulated reproduction. The assets of the REFINERY Platform (i.e., the raw data, the information, and the production rules) remain unaffected by such a reproduction in any case. In the REFINERY Platform, we first address the fact that data are generated at high velocity and are partially volatile (Characteristics III & IV) by developing a secure data store for edge devices that serves as a buffer until the data can be transmitted to the mass data provider. Our synchronization mechanism for this data store ensures that changes are always transmitted in a timely manner, as soon as connectivity is available. The Virtual Use Case Zones take into account the fact that raw data--and thus the data products derived from them--are volatile. The lifespan of these zones is limited by design, which acts as a kind of garbage collection in our data storage. The fact that data are heterogeneous (Characteristic V) is addressed in the REFINERY Platform on the one hand by using HDFS in the Raw Data Zone. That is, even unstructured data can be managed without having to transform them first. In addition, metadata about the acquired data are provided by the digital signatures, which facilitate further processing of the data. For the data preparation, we rely on a human-in-the-loop approach. A data steward defines the necessary preparation steps. In contrast to a fully automated approach, our approach therefore does not require a predefined data schema. Our approach to data preparation also addresses the fact that data refinement has to be in accordance with the data source and intended use (Characteristic VI). While the data preparation by the data steward is rather generic (whereby s/he can also take special characteristics of data sources into account), the subsequent data processing is fully geared to the intended use. The processing rules in our ontology describe how the processable