29Mar

REST is not SOA is not JSON

Posted by Elf Sternberg as chat, programming

The other day I received an interview offer from a recruiter, who forwarded me the usual list of requirements.  The fifth line of the required skills irked me:

- Knowledge of SOA (REST, JSON, etc.)

Let’s start with the fundamentals. JSON is a protocol of data exchange. You can do data exchange in just about anything: XML, YAML, HTML, JSON, BSON, IDL, even some tragic home-grown mess that only your client and server understand. But that’s all it is: a way of marshaling data at one end of an exchange between two independent programs such that at the other end it will be parsed, understood, and acted on appropriately. These are all designed to be transmitted over some mediated electronic network such as the Internet, but carrier pigeon would work.

SOA and REST are architectural decisions about how to organize your client/server software project. More than that, they are opposite decisions: choosing one means you are choosing not to use the other.  SOA (“Service Oriented Architecture”) concentrates on the service delivered, on how data is handled, whereas REST is concerned about the data being handled.  One is verb-oriented, the other is noun-oriented.

If you think this is an academic distinction, you’re right.  But it’s an important one that people screw up all the time.  Consider this analogy: going to the movies.  In a noun-oriented word, you trade money for a ticket; you trade the ticket for access; you use the access to find a seat; you use the seat to watch a movie.  That what REST does: it trades coarse documents back and forth between the client and the server describing the various records that need to be kept to accomplish a goal, which ultimately results in the client and the server agreeing on what each needs.  In a verb-oriented world, you’re not writing software dealing with money, tickets, access, seats and movies: instead, you end up writing software about the kid selling tickets, the kid taking tickets, the kid who ushers you to your seat, and the projection of the movie.  That’s what SOA does: it describes the services with which you’re provided, not the actual products you intend on handling.

I can fairly be described as a REST partisan, but then my world is full of concrete items: gene sets, stories, to-do items, gardens, potlucks, cards, poems, games.  When I program, I care about what the client and the server exchange.   In every case, the software must validate and ensure the integrity of the exchange,  but in the case of REST the medium of exchange describes what is being exchanged, not how to exchange it, and for me that makes a big difference.  When you say you want “SOA using REST,” you’re telling me you don’t really understand either.

4 Responses to REST is not SOA is not JSON

Chris

March 30th, 2012 at 4:09 pm

That is an interesting distinction. I’m new to REST and I’m mainly using it because it syncs well with backbone.js. ASP.NET MVC 4 now supports REST with their new webapi. But, I honestly didn’t know the difference between SOA and REST. The way you explain it makes sense. I always thought that REST was just a way to simplify how URLs are constructed to naviagate and fetch data from the server.

Jason

September 27th, 2012 at 7:50 am

I think it’s important to point out that when most people talk about using REST within an SOA styled service, they are referring to REST Web Services. In that context it DOES make sense since the REST Web Services then strictly becomes the transport technology. (e.g., vs. SOAP).

“When you say you want ‘SOA using REST,’ you’re telling me you don’t really understand either.”
—I think you should chill a bit and let people explain what they mean before you jump to conclusions

Ralf

December 15th, 2012 at 12:12 am

Hi Jason,
Indeed there’s nothing like a REST Web Service, because REST means accessing entities; look at Wikipedia for definition. I think you are talking about RESTful(!) Web Services.

Surya

October 17th, 2017 at 3:57 pm

SOA is a layer of web services which can be implemented using service based technologies such as SOAP, CORBA, Jini, REST, etc.

So the requirement SOA (REST, JSON), etc. is very accurate.

Somewhere you got carried away by tech terms called VERBS and NOUNS.

Comment Form

Subscribe to Feed

Categories

Calendar

March 2012
M T W T F S S
« Feb   Apr »
 1234
567891011
12131415161718
19202122232425
262728293031