1. Web Server Design Week 16 Old Dominion University
Department of Computer Science
CS 495/595 Spring 2012
Michael L. Nelson
04/24/12

2. Representational State Transfer
http is an implementation of REST
REST is best understood in contrast to Remote Procedure Call (RPC) style interfaces like SOAP
The simplest explanation is RESTful URIs are nouns, and RPC URIs are verbs
it is not true that REST URIs do not have arguments / query strings
Philosophies:
RPC: http is just a transport protocol to tunnel an application-specific protocol; other protocols (e.g., SMTP or future protocols) can be used too
REST (http implementation): http already has basic mechanisms for almost anything you need and will be around forever. Embrace it in your system design.

3. All You Need is CRUD… Operation SQL HTTP Create Insert POST, PUT
Read/Retrieve
Select
GET
Update
PUT
Delete/Destroy
Delete
DELETE

4. Example Design RPC: REST:
RPC:
(one for each user - where {user} is either the user name or the user id)
(one for each location - where {location} is the location name or the location id)
REST:
adapted from:

5. Amazon S3 “Simple Storage Service” Premise: http://aws.amazon.com/s3
part of a family of Amazon Web Services (AWS), including “Elastic Compute Cloud (EC2)” and “Simple Queueing Service (SQS)”
Premise:
cheap, remote storage service accessible via http
no initial fee, no maintenance fee
$0.11 per GB/month storage (first 50TB)
$0.12 per GB/month transferred (first 10TB)
private/public X read/write access available

6. Core Concepts Registration: Bucket Object AWS access key ID
semantic free name space for your account
Secret access key
used to authenticate to AWS
Bucket
namespace for referencing your objects; must be globally unique
you can have buckets per AWS access key
buckets hold 0 or more objects
Object
files (placed in buckets); up to 5GB in a single object
“key” is the identifier for the object placed in a bucket

7. Access Points SOAP and REST interfaces provided
3 different URLs for REST access:
Where:
bucket = your namespace
key = identifier of the object in the bucket
For more info:

8. Examples: These are the same (& real):
These would be the same (but not real):

9. Authenticating to AWS Can authenticate to AWS via:
“Authorization” http header using the AWS authentication scheme
cf. “Basic” & “Digest in RFC-2616
URL arguments
HMAC: Keyed-Hashing for Message Authentication
RFC-2104:

10. A Tour of the REST API for S3

11. GData: Atom + REST http://en.wikipedia.org/wiki/Atom_(standard)