How to access Dataset's metadata

Starting with the same Dataset as m_goldberg in his answer

ds = Dataset[{<|"a" -> 1, "b" -> "x", "c" -> {1/2}|>, 
              <|"a" -> 2, "b" -> "y", "c" -> {"a", {}, 1/2}|>}]

The same information can be extracted using

Needs["Dataset`"] 
GetData@ds
GetRawData@ds
GetType@ds
ToDatasetHandle@ds

One can get all these information at once using

DatasetPart@ds

This is what I able to extract.

ds = 
  Dataset[
    {<|"a" -> 1, "b" -> "x", "c" -> {1/2}|>, 
     <|"a" -> 2, "b" -> "y", "c" -> {"a", {}, 1/2}|>}]

{data, types, id} = 
  ToExpression[StringReplace[ToString @ FullForm[ds], "Dataset" -> "List"]];

Dataset[data]

types

which has the raw input form

TypeSystem`Vector[
  TypeSystem`Struct[
    {"a", "b", "c"}, 
    {TypeSystem`Atom[Integer], TypeSystem`Atom[String], 
      TypeSystem`Vector[TypeSystem`AnyType, TypeSystem`AnyLength]}],
  2]

id

<|"ID" -> 125700882739855|>

I think it is interesting that code editor has special formatting for the type metadata.