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Content negotiation. Content negotiation is a mechanism defined in the HTTP specification that makes it possible to serve different versions of a document (or more generally, a resource representation) at the same URI, so that user agents can specify which version fit their capabilities the best. One classical use of this mechanism is to serve an image in GIF or PNG format, so that a browser that cannot display PNG images (e.g. MS Internet Explorer 4) will be served the GIF version. To summarize how this works, when a user agent submits a request to a server, the user agent informs the server what media types it understands with ratings of how well it understands them. More precisely, the user agent provides an Accept HTTP header that lists acceptable media types and associated quality factors.

So, a resource may be available in several different representations. Accept-Language: de Note that this preference will only be applied when there is a choice of representations and they vary by language. Dereferencable URIs. A dereferenceable Uniform Resource Identifier or dereferenceable URI is a resource retrieval mechanism that uses any of the internet protocols (e.g. HTTP) to obtain a copy or representation of the resource it identifies. In the context of traditional HTML web pages, this is the normal and obvious way of working: A URI refers to the page, and when requested the web server returns a copy of it. In other non-dereferenceable contexts, such as XML Schema, the namespace identifier is still a URI, but this is simply an identifier (i.e. a namespace name). There is no intention that this can or should be dereferenced.

There is even a separate attribute, schemaLocation, which may contain a dereferenceable URI that does point to a copy of the schema document. In the case of Linked Data, the representation takes the form of a document (typically HTML or XML) that describes the resource that the URI identifies. Background[edit] Formats[edit] Hash URI example[edit] Slash URI example[edit] Summary[edit] Dereference. English[edit] Etymology[edit] de- +‎ reference Pronunciation[edit] (UK) IPA(key): /dɪˈɹɛfɹəns/ Verb[edit] dereference (third-person singular simple present dereferences, present participle dereferencing, simple past and past participle dereferenced) (programming, of a memory location) To obtain the value stored therein in an execution context which interprets that value as the address of a memory location(programming, of a pointer) to access the thing to which the pointer points.

Translations[edit] The translations below need to be checked and inserted above into the appropriate translation tables, removing any numbers. See also[edit] pointer. Publishing RDF. W3C Working Group Note 28 August 2008 This version: Latest version: Previous version: Editors: Diego Berrueta, Fundación CTIC Jon Phipps, Cornell University Library Previous Editors: Alistair Miles, STFC Rutherford Appleton Laboratory Thomas Baker, Goettingen State and University Library Ralph Swick, W3C Copyright © 2008 W3C® (MIT, ERCIM, Keio), All Rights Reserved.

Abstract This document describes best practice recipes for publishing vocabularies or ontologies on the Web (in RDF Schema or OWL). Status of this Document This section describes the status of this document at the time of its publication. This document was prepared by the Semantic Web Deployment Working Group (SWD), based on previous work by the Semantic Web Best Practices and Deployment Working Group (SWBPD). This document is a Note documenting some best practices. Table of Contents Introduction. Abstractions in Web architecture. Up to Design Issues Progress in communications technology has ben characterizsed by a movement from lower to higher levels of abstraction. When, first, computers were connected by telephone wires, then you would have to run a special program to make one connect to another. Then you could make the second connect to a third, but you had to know how to use the second one.

Mail and news would be passed around by computters calling each other late at night. Email addresses for a while contained a list of computers to pass the message through (timbl@mcvax! Cernvax! It's not the wires -- it's the computers The ability to use this communication power between computers wasn't powerfully useful until the Internet.

This made life very much easier. It's not the computers -- it's the documents This power of communication between computers wasn't really easily usable by normal people until the Web came along. Now the user is apparently in a web of interconnected documents. Up to Design Issues Tim BL.