Serialization vs. Archiving?

Question

The iOS docs differentiate between "serializing" and "archiving." Is this a general distinction (i.e., holds in other languages) or is it specific to Objective-C? Also, what is the difference between these two?

Answer 1

This is a case of one being the other some (but not all) of the time.

Wikipedia has this to say about serialization:

"Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, or transmitted across a network connection link to be "resurrected" later in the same or another computer environment"

So, archiving may only be serialization, but it could also be the combination of serialization and compresssion, for example. Or perhaps it adds some kind of header info. So serialization is a form of archive, but an archive is not necessarily a serialization.

This isn't really specific to iOS - these terms are thrown around all over. Their specific meaning in the context of iOS could be quite specific, though.

Answer 2

I was actually trying to look for their difference from IOS perspective. Adding the following for people interested :

Purpose:
Archiving is used to store object graphs. complete data model can be archived and restored easily. The way Nib files work can be considered as example for archiving.

Serialization is used for storing arbitrary hierarchy of objects.
The wat plist files work can be considered as example fo serializations.

Differences(excerpts from Archives programing guide):
"The archive preserves the identity of every object in the graph and all the relationships it has with all the other objects in the graph."
Every object encoded within the context of rootObject invocation is tracked. If the coder is asked to encode an object more than once, the coder encodes a reference to the first encoding instead of encoding the object again.

"The serialization only preserves the values of the objects and their position in the hierarchy. Multiple references to the same value object might result in multiple objects when deserialized. The mutability of the objects is not maintained."

Implementation differences:
Any object that implements NSCoding protocol can be archived where as Only instances of NSArray, NSDictionary, NSString, NSDate, NSNumber, and NSData (and some of their subclasses) can be serialized. The contents of array and dictionary objects must also contain only objects of these few classes.

When to Use:
property lists(serialization) should be used for data that consists primarily of strings and numbers. They are very inefficient when used with large blocks of binary data.
It is worthy to Archive objects other than plist objects or storing large blocks of data.