Since this is complicated, I would like to give some examples of what all these parts are.
Let's suppose you are reading this in your web browser, via that online version of this that I am providing. What do these parts correspond to?
- Concrete parts: This chapter is composed of some text, and some pictures. The text (represented in HTML) and pictures are each individual files sitting on a hard drive somewhere in Pennsylvania (I think...).
- Sender: That would be me, but not because I wrote this essay. It's because it's my web server and I'm ultimately responsible for what it serves. As the sender, it's my responsibility to ensure I have the proper permissions to send the concrete parts to you. Since I authored the concrete parts in question it is happily quite easy to grant myself permission to serve the parts out. I'm such a nice guy, I'm not even asking me to pay for the privilege!
- Assembler: The web server software on jerf.org.
- Message: The physical incarnation of the message is a stream of bits representing the images and text going to your computer.
- Decoder: The computer you are using, and more specifically the web browsing software, is decoding the message which is just a series of electrical impulses into a visual format you can perceive.
- Human-experienced message: The very photons coming into your eyes, or sound coming into your ears, or however you are perceiving this webpage.
Remember this is all at the conceptual level, not necessary a literal level. For our purposes here a "webpage" is one message, even though at the physical level the decoder (web browser) and the assembler (web server) may actually have a two-way communication. In addition, the "assembler" may not literally correspond to one physical entity either, as multiple webservers may be used to assemble a single webpage. For example, many web sites split their "content" and "images" server for technical reasons. As usual, what really matters in this model are the people. The critical points of view are the ones that the receiver and the author have; once you have that, then you can draw the line around the "assembler" and "decoder" with confidence, even if they are very complicated machines. The technology is not important.
A more traditional example: Suppose this had been published as a traditional book.
- Concrete parts: The exact same concrete parts used for the web page would be used for the book. The text would not be represeted in HTML, it would be TEX or some other typesetting language, and the images would be in a different format, but to the extent possible, they would represent the same text and pictures.
- Sender: In this case, it would be the book publisher, because they would have final authority over what goes into the book. This despite the fact that they did not author a significant amount of the concrete parts going into the book. They would get a logo on the back cover and similarly inconsequential things, so they do have a little content, but it's a vanishing fraction of the whole.
- Assembler: In this case, the book publishing machine, which is probably software driven nowadays but you could pretend there are no computers involved for the sake of argument if you wish.
- Message: The actual book.
- Decoder: Also the actual book; it "decodes" my content by the act of existing and having light fall on it, which then enters your eyes.
- Human-experienced message: Also for all practical purposes the book itself; they should all be effectively identical so there's no benefit to getting more technical then that.