What is the difference between a hierarchical structure and a chain$-$type structure in a classification and coding scheme?

In a hierarchical structure, each symbol has a fixed interpretation, while in a chain$-$type structure, interpretation depends on preceding symbols.

Chain$-$type structure is also known as monocode, while hierarchical structure is called polycode.

In a hierarchical structure, the interpretation of each successive symbol depends on the values of preceding symbols while in a chain$-$type structure the interpretation of each symbol in the sequen always the same. $q,$

$$ Hierarchical structure relies on alphabetical order, while chain$-$type structure uses numerical value

$$ Both hierarchical and chain$-$type structures interpret symbols independently of each other.