The document discusses RESTful web services and Resource Oriented Architecture (ROA). It defines REST and its constraints including client-server architecture, statelessness, cacheability, uniform interface and layered system. It then explains ROA and how resources are addressed and represented in a RESTful system. Key concepts like addressability, statelessness, representations, links and connectedness, uniform interface and safety are covered in relation to ROA. The document provides examples and discusses designing a RESTful API for a content management system.

1. Smart IT Engineering Ltd. RESTful Web Services Imran M Yousuf Smart IT Engineering Ltd.

2. Smart IT Engineering Ltd. What's not covered Comparison between various Web Service technologies

3. Hands on tutorial on how code a RESTful WS

4. Details of how HTTP works

5. Details on various media formats

6. Smart IT Engineering Ltd. What to expect REST Definition

7. Discussion on its constraints

8. WWW RESTful Web Service Resource Oriented Architecture (ROA)

9. Constraints of ROA

10. Examples

11. Smart IT Engineering Ltd. What to expect A Design Case Study

12. Questions

13. Smart IT Engineering Ltd. What is REST RE presentational S tate T ransfer

14. Proposed by Dr. Roy Thomas Fielding in his PhD dissertation titled - “Architectural Styles and the Design of Network-based Software Architectures”

15. Smart IT Engineering Ltd. What is REST RE presentational S tate T ransfer

16. REST is an architectural style composed of specific constraints.

17. The Constraints - - Client-Server - Stateless - Cache - Uniform Interface - Layered System - Code-On-Demand (Optional)

18. Smart IT Engineering Ltd. REST Constraints Client-Server No restrictions on the nature of the client

19. No restrictions on the number of the clients

20. No restriction on communication medium / protocol Client (Browser) Client (CLI – curl, wget) Client (Desktop) Network Client (Mobile) Client (Another System)

21. Smart IT Engineering Ltd. REST Constraints Client-Server Separate data storage concerns

22. Improve user interface portability across multiple platforms

23. Improve scalability by simplifying server components

24. Components evolve independently

25. Smart IT Engineering Ltd. REST Constraints Stateless “ ... each request from client to server must contain all of the information necessary to understand the request, and cannot take advantage of any stored context on the server.” Advantages Visibility Reliability Scalability

26. Smart IT Engineering Ltd. REST Constraints Cache “ ... the data within a response to a request be implicitly or explicitly labeled as cacheable or non-cacheable. If a response is cacheable, then a client cache is given the right to reuse that response data for later, equivalent requests.” Advantages Efficient Scalability Performance

27. Smart IT Engineering Ltd. REST Constraints Layered System The layered system style or also popularly referred to as n-layer system allows an architecture to be composed of hierarchical layers by constraining component behavior such that each component cannot "see" beyond the immediate layer with which they are interacting. Code-On-Demand Allows client functionality to be extended by downloading and executing code in the form of applets or scripts . This simplifies clients by reducing the number of features required to be pre-implemented.

28. Smart IT Engineering Ltd. REST Constraints Uniform Interface Central distinguishing feature of REST Involves four constraints to define 'uniform interface' for REST systems. Identification of resources

29. Manipulation of resources through representations

30. Self-descriptive messages

31. HATEOAS ( H ypermedia A s T he E ngine O f A pplication S tate)

32. Smart IT Engineering Ltd. REST Constraints Uniform Interface - Resource Any concept that might be the target of an web-author's hypertext reference must fit within the definition of a resource.

33. A resource is a conceptual mapping to a set of entities , not the entity that corresponds to the mapping at any particular point in time.

34. If compared of Object Oriented aproach, Object if referrrable is a resource.

35. Examples of resources would Books, A Book, An Author, Authors, Authors of a Book, A Publisher, Categories of a Book, A Category etc.

36. Smart IT Engineering Ltd. REST Constraints Uniform Interface – Representations & Messages A representation is a sequence of bytes describing a resource in a particular format.

37. Other commonly used but less precise names for a representation include: document, file, and HTTP message entity, instance, or variant.

38. Message consists of control data, metadata, messages and in some cases hyperlinks to resources.

39. Examples: Images (image/jpg, image/png, etc.), Markups (text/html, application/xml etc.) and more.

40. Smart IT Engineering Ltd. REST Constraints Uniform Interface – HATEOAS A hypermedia in each server response will contain links that correspond to all the actions that the client can currently perform.

41. Therefore, dependent on the current application state, every server response describes the new actions that are available.

42. The server can change the range of allowable responses in a dynamic way, and a client should adapt its behavior to these changes.

43. A client of a RESTful application need only know a single fixed URL to access it.

44. Smart IT Engineering Ltd. REST Constraints Uniform Interface – HATEOAS All future actions should be discoverable dynamically from hypermedia links included in the representations of the resources that are returned from that URL.

45. The link relations should be standardized , so that the client knows what selecting that state transition means.

46. Standardized media types are also expected to be understood by any client that might use the API.

47. Application state transitions are driven by a combination of the known processing rules for each media type, client selection from the server-provided choices in representations received, and the user's manipulation of those representations. Thus interactions are driven by hypermedia .

48. Smart IT Engineering Ltd. REST What is the biggest known RESTful System on planet Earth?

49. Smart IT Engineering Ltd. REST World Wide Web a.k.a Internet HTTP Web Pages HTML pages are hypermedia CSS