Uniform Resource Identifier (URI)

Web Architecture [./]
Fall 2010 — INFO 290 (CCN 42605)

Erik WildeUC Berkeley School of Information, UC Berkeley School of Information
2010-10-12

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E. Wilde: Uniform Resource Identifier (URI)

(2) Abstract

The Web's architecture has very simple principles revolving around the ideas of placing a heavy emphasis on a consistent and global identification mechanism for resources, a standardized way of how resource representations can be retrieved, and a standardized way of how resource representations should be usable by using standardized media types. For identification, the Web uses the concept of a Uniform Resource Identifier (URI), and the main properties of URIs are that they make resources identifiable within a certain scheme, which then determines how resources are identified within that scheme, and what methods can be used for interacting with them.

E. Wilde: Uniform Resource Identifier (URI)

(3) Web Server Service

Web servers do more than just deliver files
They receive a request for acting on a resource
- this may be a simple file retrieval
- additional information is available from the request's header fields [Hypertext Transfer Protocol (HTTP); HTTP Header Fields (1)]
- the request URI may contain additional query information
- the request may transmit complex data (such as a form submission)
Processing can mean anything, it is transparent for the client
- the result of processing yields a resource representation
- in many cases, a Web server is just part of an application
- the application server is the application-specific logic

Uniform Resource Identifier (URI)

Outline (Uniform Resource Identifier (URI))

Uniform Resource Identifier (URI) [2]

Uniform Resource Identifier (URI) E. Wilde: Uniform Resource Identifier (URI)

(5) Resource Identification

The Web is centered around resources
- HTTP has been designed to manipulate resources
- HTTP provides methods for getting, putting, updating, and even deleting resources
Resources are useful abstractions for interfaces
- instead of an API, interaction is built around manipulating resources
- APIs change and bind closely, documents can better withstand change and bind loosely
- the whole Web is built around resources, not APIs

Uniform Resource Identifier (URI) E. Wilde: Uniform Resource Identifier (URI)

(6) URI Schemes

URI = scheme ":" hier-part [ "?" query ] [ "#" fragment ]

http://dret.net/lectures/web-fall10/foundations#uri-schemes

URIs in their general case are very simple
- the scheme identifies how resources are identified
- the identification may be hierarchical or non-hierarchical
Many URI schemes are hierarchical
- it is then possible to use relative URIs such as in a href="../"
- the slash character is not just a character, in URIs it has semantics
Query components specify additional information
- it is non-hierarchical information further identifying the resource
- in most cases, it can be regarded as input to the resource

Uniform Resource Identifier (URI)

Web Architecture [./]
Fall 2010 — INFO 290 (CCN 42605)

Erik WildeUC Berkeley School of Information, UC Berkeley School of Information
2010-10-12

Contents

(2) Abstract

(3) Web Server Service

Uniform Resource Identifier (URI)

Outline (Uniform Resource Identifier (URI))

(5) Resource Identification

(6) URI Schemes

(7) Conclusions

Uniform Resource Identifier (URI)

Web Architecture [./]Fall 2010 — INFO 290 (CCN 42605)

Erik WildeUC Berkeley School of Information, UC Berkeley School of Information2010-10-12

Contents

(2) Abstract

(3) Web Server Service

Uniform Resource Identifier (URI)

Outline (Uniform Resource Identifier (URI))

(5) Resource Identification

(6) URI Schemes

(7) Conclusions

Web Architecture [./]
Fall 2010 — INFO 290 (CCN 42605)

Erik WildeUC Berkeley School of Information, UC Berkeley School of Information
2010-10-12