Partial updates are somewhat problematic in the world of RESTful applications. Currently, we use POST and PUT to write data or update it, but on sub-properties of data updates, it actually can get somewhat hard to code for when you get into the more subtle application logic and error management, let alone on datasets that are very large or have very deeply nested data structures in a single JSON object, for example.
But, regardless, PUT and POST have done a satisfactory job up until now, and nobody really needs to use PATCH in a relational context. But therein lies an interesting point: data is getting bigger, and naturally, semantic data is starting to become much more prevalent, and its URI-based. It logically follows that if data continues to become more semantic, and you’re dealing more often in deeply nested structures, you’ll need a URI-based updating method that can be more flexible than PUT and POST. But you don’t have to take my word for it, lets ask an expert.