Abstract
Since the traditional relational database systems are not capable of following the contemporary requirements on Big Data processing, a family of NoSQL databases emerged. It is not an exception for such systems not to require an explicit schema for the data they store.
Nevertheless, application developers must maintain at least the so-called implicit schema. In certain situations, however, the presence of an explicit schema is still necessary, and so it makes sense to propose methods capable of schema inference just from the structure of the available data.
In the context of document NoSQL databases, namely those assuming the JSON data format, we focus on several representatives of the existing inference approaches and provide their thorough comparison. Although they are often based on similar principles, their features, support for the detection of references, union types, or required and optional properties differ greatly.
We believe that without adequately tackling their disadvantages we identified, uniform schema inference and modeling of the multi-model data simply cannot be pursued straightforwardly.