Rather than use a binary format by default, as in ADO classic, the DataSet default is XML serialization and marshaling. This means that you can populate DataSet from non-Microsoft data sources, and the data is consumable from non-Microsoft platforms. Because DataSet marshals as an XML document, it is natively supported without transformation by Web Services.
The .NET platform includes two libraries that serialize and deserialize classes in XML format:
System.Runtime.Serialization is used for marshaling in .NET implementations.
System.Xml.Serialization is used in Web Services to support unlike implementations.
DataSet is compatible with both of them.
System.Runtime.Serialization serializes .NET classes ...