Tabular data is regarded as structured data, while other data types such as images, audio, video, text are regarded as unstructured data.
I am confused that, taking images as an example, they are just stored in computers as matrices or high-dimensional tensors, which obviously belong to a certain type of structure, so why are they still called unstructured data?
And even more generally speaking, digital data of any data type should have a certain type of structure, at least from a storage perspective in computers, so what essentially distinguishes between unstructured data and tabular data (structured data)?
And there is also a related term in machine learning called structured learning, which as far as I know refers to learning a model whose output is of dimension higher than 1, like output an image instead of a vector.
But just as mentioned, images are typical unstructured data, so it seems to implicate that the meaning of
structured learning conflicts with its meaning in
structured data, which confuses me a lot.