Constructs a physical schema mapping instance using the result returned from IConnection::CreateSchemaMapping OR using the result of executing an IDescribeSchemaMapping command. This constructor is provided in order that clients are provided a mechanism to downcast from the FDO PhysicalSchemaMapping base class to an FDO Provider specific class that derives from PhysicalSchemaMapping. This constructor is the only mechanism provided by the FDO Managed API that will allow the client to correctly construct a provider specific PhysicalSchemaMapping class. NOTE: If the Provider name associated to the input parameter schemaMapping does not correspond to the provider name of the expected FDO Provider, and InvalidArgumentException will be thrown.