Identifying the data type

if i understand the question correctly, it first looks at the file extension on the file.
then it looks for the program that the file may have come with, to use it.
if it is unfamiliar with the file, or if it is not connected with an application/program, then it looks for that same extension and uses the program that any similiar files are using.
if it still cannot ascertain what program uses that file extension. then it allows you to choose the application/program to open it.
hope thishelps.

Each software program comes with its oun recognized set of Data Types and an "engine" (or block of code) that processes stored values on a PC (or server). With database software (like Access or Oracle) developers MUST assign a Data Type every time they create a "bucket" to store stuff in (even if its a Data Type that accepts anything because they don't know what's coming such as a Variant Data Type). The software "engine" then tells the CPU (or PC engine) how to interpret the next incoming value as things are processed at lightning speed. The same process is esentially true for almost every type of software but only Database software (and a few spreadsheet fields) allows developers to "pre-define" Data Types.

Hope this helps.