<p>Multi-dimensional arrays (also known as raster data, gridded data, or datacubes) are key, if not essential, in many science and engineering domains. In the case of Earth sciences, a significant amount of the data that is produced falls into the category of array data. That being said, the amount of data that is produced daily from this field is huge. This makes it hard for researchers to analyze and retrieve any valuable insight from it. 1-D sensor data, 2-D satellite imagery, 3-D x/y/t image time series and x/y/z subsurface voxel data, 4-D x/y/z/t atmospheric and ocean data often produce dozens of Terabytes of data every day, and the rate is only expected to increase in the future. In response, Array Databases systems were specifically designed and constructed to provide modeling, storage, and processing support for multi-dimensional arrays. They offer a declarative query language for flexible data retrieval and some, e.g., rasdaman, provide federation processing and standard-based query capabilities compliant with OGC standards&#160;such as WCS, WCPS, and WMS. However, despite these advances, the gap between efficient information retrieval and the actual application of this data remains very broad, especially in the domain of artificial intelligence AI and machine learning ML.</p><p>In this contribution, we present the state-of-art in performing ML through Array Databases. First, a motivating example is introduced from the Deep Rain Project which aims at enhancing rainfall prediction accuracy in mountainous areas by implementing ML code on top of an Array Database. Deep Rain also explores novel methods for training prediction models by implementing server-side ML processing inside the database. A brief introduction of the Array Database rasdaman that is used in this project is also provided featuring its standard-based query capabilities and scalable federation processing features that are required for rainfall data processing. Next, the workflow approach for ML and Array Databases that is employed in the Deep Rain project is described in detail listing the benefits of using an Array Database with declarative query language capabilities in the machine learning pipeline. A concrete use case will be used to illustrate step by step how these tools integrate. Next, an alternative approach will be presented where ML is done inside the Array Database using user-defined functions UDFs. Finally,&#160; a detailed comparison between the UDF and workflow approach is presented explaining their challenges and benefits.</p>
