Clouds: About files in Google Drive

There are two types of files available in Google Drive:

TElGoogleDriveFile - represents a general file. Such files can be copied, moved, deleted, etc. Also it is possible to write data to such file and read data from it.
TElGoogleDocument - represents a document created by Google Docs service. Documents do not have size. Data to documents cannot be written directly. Instead, data to documents must be imported and its structure will be changed on the server. Also, there is no way to read the whole data from documents. Instead, documents must be exported to a certain file format depending on document type. So, because there is no way to control document structure on the server, TElGoogleDocument class does not contain methods to import and export documents. Other operations with documents, like copying, moving, renaming and deleting, can be performed the same way as with general files.