## 4 The REFINERY Platform  
In our REFINERY Platform, we aim to provide comprehensive support for data administration, starting from any data source and ending with tailored data products. Despite this holistic view of the data administration process, the REFINERY Platform consists of a wide range of individual solutions for each process step, e.g., data acquisition from smart devices and databases, customizable data preparation rules, secure data management, and making the data products visible to data consumers. The main focus here is on ensuring that all concepts are geared to the specific characteristics of data (see Section 2). This includes in particular that the commodity 'data' is handled reliably. On the one hand, this means that it must be feasible for data producers or data subjects to regulate data processing in accordance with their data privacy and confidentiality requirements. On the other hand, the customers of the data products, i.e., the data consumers, must be able to fully trust the authenticity of the data and be reassured that the data are of the promised quality. A high-level overview of the general concept of the REFINERY Platform is shown in Figure 2.  
Due to the IoT, two different types of data sources need to be supported by a data administration platform currently. On the one hand, there is a multitude of smart devices that are able to collect a plethora of different data via connected sensors and share them due to their connectivity. On the other hand, there are mass storage devices in the form of databases, both relational databases and NoSQL data stores, which provide data at rest. In the REFINERY Platform, both types of data sources can be integrated. During acquisition, the data are verified by the REFINERY Platform in terms of whether it possesses  
Figure 2: High-Level Overview of the General Concept of the REFINERY Platform. the specified properties, e.g., regarding data quality. In addition, the data sources can assert privacy requirements, which are then enforced in the REFINERY Platform in the form of PET, e.g., privacy filters. All three types of PET are supported, i.e., obfuscation techniques for users, statistical disclosure control for mass data providers, and distribution of data across multiple trusted third parties. The received data prepared in this way are subsequently processed semiautomatically in the REFINERY Platform and data products are generated. For this purpose, domain experts specify rules for the data cleansing and data transformation steps to be applied to the data. These rules can then be automatically applied to the acquired raw data. The semiautomatic approach is necessary to generate customized and high-quality data products, which would not be possible without the involvement of human experts. However, the resulting rule base increasingly reduces the experts' workload in this context, as they can draw on already specified preparation rules (either in parts or as a whole). Then, both the raw data and the data products have to be managed. The REFINERY Platform uses a big data storage system that enables efficient management of the raw data and the processed data, as well as demand-oriented access to the actual data products. Due to the high economic value of these intangible commodities and digital products, we apply blockchain technologies to secure them against malicious tampering and deletion. Finally, it must be possible for customers to find the products they need from the vast amount of available data products. For this purpose, the REFINERY Platform has data management structures that support an electronic storefront, which can be used to search the product range efficiently. The metadata gathered and generated by the REFINERY Platform enables straightforward information retrieval. In addition, customers can use the metadata to inform themselves about existing raw data and place orders for customized data products.