A Web 2.0 Glossary (Part 2 of 2)

This is the continuation of the post: A Web 2.0 Glossary (Part 1 of 2).

• Podcast (iPOD broadCAST): An audio broadcast that has been converted to an MP3 or other audio format for playback on a digital music player (iPod) or computer. A podcast is distinguishable from other digital media formats by its ability to be syndicated using RSS/Atom, subscribed to, and downloaded automatically using an aggregator like iTunes.

• RDF (Resource Description Framework): The core mechanism of the Semantic Web (in the classic sense), RDF is a metadata model that enables machine-readable statements to be made about resources. These statements have the form of subject-predicate-object expressions (“tripples”), where the subject and predicate are both resources (often, but not necessarily pointed to by URIs), and where the object is a third resource, or a character string literal. For instance, the subject might be a URI that points to an online article, the predicate might be another URI that points to a machine-readable definition of a given relationship (such as “author”), and the object might be a character string literal of the author’s name. RDF is often (but not necessarily) serialized as XML. The original version of RSS made use of RDF (RDF Site Summary).

• REST (Representational State Transfer): A software architectural style designed for distributed hypermedia systems, originally introduced by Roy Fielding in his 2000 Doctoral Dissertation. Rather than objects exposing any number of specialized methods, REST’s architectural principles call for resources that are addressed by a uniform interface, consisting of a universal syntax for identifying those resources and a limited set of operations for invoking state changes on their representations (think URIs with GET and POST). While in broad terms REST describes how much of the Web actually works, in its more strict sense it can be taken to apply principally to such protocols as RSS and ATOM, both used extensively by blogs. Implementations that achieve the style’s goals (e.g., cacheability, statelessness, universal discovery and interoperability) are said to be RESTful. REST is often contrasted with Web Service protocols like SOAP and XML-RPC.

• RIA: A Rich Internet Application, that is, a browser-based app that provides a user experience similar to that of traditional desktop apps. RIAs may be designed to be connected only part of the time to the Internet, something that the new browser extension Google Gears, for instance, will help to make possible.

• RPC (Remote Procedure Call): A method for executing a process/procedure/program on another computer across a network. Often used in RIAs and SPAs, this is the most popular method of client/server communication in AJAX.

• RSS (Really Simple Syndication): An XML based method of providing content via the internet; typically a news story, blog post, or link to an audio file (see podcast). An RSS news reader can monitor (or subscribe to) an rss file on the internet (rss feed), and download changes automatically.

• Semantic Web: A vision of the Web (embodied in evolving design principles, working groups and enabling technologies) in which meaningful content is expressed not only in natural language but also in machine-readable formats that allow software agents to find, share and integrate such information on behalf of its ultimate human consumers. Tim Berners-Lee originally described the Semantic Web as one in which computers would be capable of analyzing all the data on the Web, including all transactions between humans and computers. While this classic vision of the Semantic Web, based on technologies like RDF, remains largely unrealized, it has more recently been claimed that the semantics available in (X)HTML are making for a more practical and evolutionary “lowercase semantic Web” via applications such as blogs and technologies like microformats. Here the vision is not of a Web whose semantics are globally defined in a machine-readable way, but rather of what Tantek Celik and Kevin Marks call “small pieces [of semantic meaning] loosely joined.”

• SOAP: An acronym that originally stood for Simple Object Access Protocol, uses xml to format and contain data and was popularized by OOP languages for exchanging objects via web services or RPC. SOAP messages typically contain three main elements soap:Envelope, soap:Header, and soap:Body.

• SPA: A Single Page Application, is another name for a browser based app that is typically rich like an RIA and does all its work in a single page. In other words an SPA never loads a brand new page and always uses a set URL.

• Tagcloud: A tagcloud is a visualization of a content space as a cloud of terms or phrases. Generally the importance or activity of each term is indicated by the size or visual style of the words in the tag cloud. Example – http://www.flickr.com/photos/tags/

• Web Services: The term refers to clients and servers that communicate using XML messages that follow the SOAP-standard. Common in both the field and the terminology is the assumption that there is also a machine readable description of the operations supported by the server, a description in the WSDL. The latter is not a requirement of SOAP endpoint, but it is a prerequisite for automated client-side code generation in the mainstream Java and .NET SOAP frameworks.

• Wisdom of the Crowds: A term from James Surowiecki’s book of the same name showing the accuracy of crowds in solving problems with relatively little information. Many Web 2.0 business models attempt to use the Internet “crowds” to solve problems (see Crowdsourcing) or reveal trends (see Digg.com). Scant attention is given to the obvious downside of the idea such as mob mentality and the rise of mediocrity via “social proof.” Basically social proof forces some users to assume value just because of the crowd’s justification of value such a high digg ranking.

• XML (Extensible Markup Language): Developed by the W3C in 1996, XML is a format for tagging and organizing content into a usable and meaningful text based structure. Often used in information exchange it allows anyone to define, validate and interpret documents that can store nearly any type of data. Sometimes criticized because of the overhead associated with its tag based format.