To view recording of this webinar please use below URL: http://wso2.com/library/webinars/2015/09/resource-oriented-architecture/ Any given business, organization or entity is built with resources. It can be human capital, digital assets, services or products among other things. These activities often interact with each other creating a value network. A good example of this is when human resources interact with digital assets to perform a service. We as computer scientists, have been trying to simplify this interaction flow for quite some time. The field of distributed systems and semantic web are dedicated to solving problems in this domain. RESTful services and the ecosystem around it have now simplified this interaction to a great level. Being able to interact with a resource with basic actions in a secure manner is a great achievement. This webinar will discuss The of history of ROA Its current landscape ROA and microservices New development around the architecture pattern

1. Resource Oriented Architecture
Sep-15-2015
Nuwan Bandara
@nuwanbando
Solutions Architect, WSO2

2. Software/Computer Systems & Humans
➡ Single most connected artificial entity to
humans at present
➡ Rapidly changing and progressing
➡ Increasingly becoming a ubiquitous
entity to consume information and act
on it
➡ Rules are rapidly changing: Industrial
revolution for the software industry is
yet to happen

3. Human Interaction
➡ With Humans: People are Identified by a
name and can be associated to a location,
place of work/study, a profession etc.
➡ With objects: People identify objects by a
name and can be associated to a location,
type, use of, owned by etc.
➡ The interaction: Change of state -
“become a friend” or “buy a caramel latte”

4. The Common Factor
➡ Any kind of an interaction is defined by a simple protocol
➡ You identify something (i.e: name)
➡ You associate it to something to derive meaning (i.e: location)
➡ You change the state (aka interact)

5. Building A Connected Information System
➡ If interaction is the key thing in any system
➡ We need to define the entities, their associations and interactions
➡ In an HR system employee is an entity, “department”, “salary”,
“bio” are descriptors or associations to that entity
➡ In an abstract sense we interact with a resource based ecosystem
➡ Every entity and a descriptor can be represented as a resource

6. Resource Orientation Is Not A Leapfrog
➡ Object Oriented Architecture
‣ Every entity is defined as an object
‣ Objects have attributes and actions
‣ Objects have a state
➡ Service Oriented Architecture
‣ Entities are services
‣ Service has a description and a contract
‣ Interacts over the network with a defined location (address)

7. Resource Oriented Architecture (ROA)
➡ The rest of “REST”
➡ Foundations of the Semantic Web
➡ Building a ubiquitous computing ecosystem
➡ Describing a system as a self discoverable entity
➡ Modeling a system based on its logical form (as oppose to the
technical form)

8. ROA Fundamentals
➡ Uses Representational State Transfer (REST) as the primary design
pattern
➡ Data is independent of the server and the client - The server
implementation can change over time and there can be many
clients.
➡ Loose coupling is one of the objectives of the architecture
➡ “State” is treated as actions performed against the resource

9. URLs Are The Identifiers Of Resources
➡ Resources are uniquely identifiable
‣ Uniform Resource Name (URN) is a good example
of a uniquely identifiable resource name
‣ ISBN is a classic example
➡ URN alone cannot identify a resource, there needs
to be a discovery mechanism
urn:isbn:9780345376596
https://library.org/books/9780345376596
http://wso2.com/customer/fin23324
or

10. How A URL Should Look Like In ROA
➡ Has to be a logical representation of the resource
‣ The only requirement: A resource identifier has to be an indefinite
constant
From following patterns which creates an indefinite constant ?
http://wso2.com/customer.jsp?id=fin233245
http://wso2.com/customer/v1/fin233245
http://wso2.com/customer/fin233245

11. Lets Examine
➡ {.jsp} is implantation detail
➡ Implementations change over time
http://wso2.com/customer.jsp?id=fin233245
http://wso2.com/customer/v1/fin233245
➡ {v1} is a contractual detail
➡ The resource format (structure) should not define the resource identifier
➡ However the version is an important detail, hence
http://wso2.com/customer/fin233245?version:v1

12. Identifier Information & Meta Information
➡ URL parameters as meta information
➡ Meta information do not identify the resource but add more
context/flexibility for the consumer
http://wso2.com/customer/fin233245?version:v1
http://wso2.com/report/sales/2009/qtr/3?sort=ascending

13. Freedom Of Form
➡ The format of the resource can be of many forms
http://wso2.com/customer/fin233245/book.xml
http://wso2.com/customer/fin233245/book.json
http://wso2.com/customer/fin233245/book.html
http://wso2.com/customer/fin233245
Accept: application/json
curl -H "Accept: application/json" -O http://wso2.com/customer/fin233245
vs

14. Late Binding
➡ Named references (aka “Pointers” in ROA)
‣ Actual resource is not retrieved unless its explicitly asked for
‣ A reference to the resource is passed in an orchestration
curl -H "Accept: application/json" -O http://wso2.com/customers
[“http://wso2.com/customer/fin233245”, “http://wso2.com/customer/ecom233246”]
➡ This methodology allows a system built with ROA enforce granular
level of entitlement

15. Loosely Coupled & Logically Connected
➡ Resources are identified by it’s logical meaning - URL construction (ROA
101)
‣ Independent of the server implementation - Greater flexibility for change
‣ Clients are intact - Clients are wired to the resource
➡ Following Postel's Law - Be strict in what you provide (Resource identifier,
data formats etc) but be flexible when receiving (different clients should be
able to send data in different formats)

16. Hypermedia As The Engine Of Application State
(HATEOAS)
➡ Client does not have any meaningful idea about the data sent by the
server
➡ Client can only render it
➡ Client interact with the server only via hypermedia
➡ No prior contract, client will discover possible actions by understating
the resource representation sent by the server
➡ The resource representation is state-full and sent across the hypermedia

17. Understanding HATEOAS
➡ Listing a book in the library
GET /book/9780345376596 HTTP/1.1
Host: library.org
Accept: application/json
..
HTTP/1.1 200 OK
Content-Type: application/json
Content-Length: …
{
"name": "the pale blue dot",
"ISBN": "9780345376596",
"author": "carl sagan",
"borrow": "http://library.org/book/9780345376596/borrow"
}
GET /book/9780345376596 HTTP/1.1
Host: library.org
Accept: application/json
..
HTTP/1.1 200 OK
Content-Type: application/json
Content-Length: …
{
"name": "the pale blue dot",
"ISBN": "9780345376596",
"author": "carl sagan",
"return": "http://library.org/book/9780345376596/return"
}
➡ Listing a book after its been
borrowed

18. Semantic Web & ROA
➡ Defines a structured relationship of resources (over the web)
➡ Defines the means of querying an exact resource vs arbitrary
discovery
➡ Identifies resources as edges and nodes
‣ An edge represent a data element
‣ A node describe more nodes & edges

19. Micro-Services & ROA
➡ “Micro-Services Architecture” is properly Implements SOA
➡ Micro Services complements ROA
➡ Micro service in essence is a service with the right level of granularity
performing a specific business task
➡ In a high level a “micro service” is the implementation of a resource with its
contextual details
‣ The library example: The book is a resource in the library, you can borrow
and return a book and that encapsulate the logical book in a library which
can be implemented as a micro service

20. References
➡ http://www.infoq.com/articles/roa-rest-of-rest#anch50927
➡ https://www.ics.uci.edu/~fielding/pubs/dissertation/
rest_arch_style.htm#sec_5_1
➡ https://www.ics.uci.edu/~fielding/pubs/dissertation/
rest_arch_style.htm#sec_5_2
➡ http://www.w3.org/standards/semanticweb/

21. Image References
➡ https://www.bestthinking.com/articles/computers_and_technology/
software/software_architecture/designed-for-humans
➡ http://www.socialsongbird.com/2014/08/social-media-and-human-
interaction.html
➡ https://jlmhenson20xs.wordpress.com/2013/10/22/a-great-
interaction/
➡ http://theviewinside.me/if-you-want-peace-of-mind-defeat-your-
past-by-climbing-your-own-mount-everest/