Integration across multiple data sources is very difficult. The schemas change and you have to constantly juggle the translation between different sources and s

Integration across multiple data sources is very difficult. The schemas change and you have to constantly juggle the translation between different sources and synchronization in order to keep your app working. Years I ago I worked with Oracle ERP which under the hood was just as you describe a fusion of different products from different companies that they had acquired. It was a maze of scripts converting from one format to another and thence to another, etc.