What is the difference between Serialization and Marshaling?

I know that in terms of several distributed techniques (such as RPC), the term "Marshaling" is used but don't understand how it differs from Serialization. Aren't they both transforming objects into series of bits?

Related:

What is Serialization?

What is Object Marshalling?

Solution 1:

Marshaling and serialization are loosely synonymous in the context of remote procedure call, but semantically different as a matter of intent.

In particular, marshaling is about getting parameters from here to there, while serialization is about copying structured data to or from a primitive form such as a byte stream. In this sense, serialization is one means to perform marshaling, usually implementing pass-by-value semantics.

It is also possible for an object to be marshaled by reference, in which case the data "on the wire" is simply location information for the original object. However, such an object may still be amenable to value serialization.

As @Bill mentions, there may be additional metadata such as code base location or even object implementation code.

Solution 2:

Both do one thing in common - that is serializing an Object. Serialization is used to transfer objects or to store them. But:

• Serialization: When you serialize an object, only the member data within that object is written to the byte stream; not the code that actually implements the object.
• Marshalling: Term Marshalling is used when we talk about passing Object to remote objects(RMI). In Marshalling Object is serialized(member data is serialized) + Codebase is attached.

So Serialization is part of Marshalling.

CodeBase is information that tells the receiver of Object where the implementation of this object can be found. Any program that thinks it might ever pass an object to another program that may not have seen it before must set the codebase, so that the receiver can know where to download the code from, if it doesn't have the code available locally. The receiver will, upon deserializing the object, fetch the codebase from it and load the code from that location.

Solution 3:

From the Marshalling (computer science) Wikipedia article:

The term "marshal" is considered to be synonymous with "serialize" in the Python standard library1, but the terms are not synonymous in the Java-related RFC 2713:

To "marshal" an object means to record its state and codebase(s) in such a way that when the marshalled object is "unmarshalled", a copy of the original object is obtained, possibly by automatically loading the class definitions of the object. You can marshal any object that is serializable or remote. Marshalling is like serialization, except marshalling also records codebases. Marshalling is different from serialization in that marshalling treats remote objects specially. (RFC 2713)

To "serialize" an object means to convert its state into a byte stream in such a way that the byte stream can be converted back into a copy of the object.

So, marshalling also saves the codebase of an object in the byte stream in addition to its state.

Solution 4:

I think that the main difference is that Marshalling supposedly also involves the codebase. In other words, you would not be able to marshal and unmarshal an object into a state-equivalent instance of a different class. .

Serialization just means that you can store the object and reobtain an equivalent state, even if it is an instance of another class.

That being said, they are typically synonyms.