RDF (Resource Description Framework) Interview Preparation Guide

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RDF”the Resource Description Framework”is a standard model for data interchange on the Web. RDF has features that facilitate data merging even if the underlying schemas differ, and it specifically supports the evolution of schemas over time without requiring all the data consumers to be changed.

RDF statements (or triples) can be encoded in a number of different formats, whether XML based (e.g., RDF/XML) or not (Turtle, N-triples). In general it does not really matter which of these formats (or serializations) are used to express data”the information is represented in RDF triples and the particular format is only the syntactic sugar. Most RDF tools can parse several of these serialization formats.

No. The fundamental model of RDF is independent of XML. RDF is a model describing qualified (or named) relationships between two (Web) resources, or between a Web resource and a literal. At that fundamental level, the only commonality between RDF and the XML World is the usage of the XML Schema datatypes to characterize literals in RDF. In fact, using GRDDL, a way to automate mappings from XML to RDF easily, many XML vocabularies can be considered applications of RDF.Note that one of the serialization formats of RDF is indeed based on XML (RDF/XML), and this is probably the most widely used format today. But others exist, see the separate question on RDF representation

The W3C Data Access Working Group has developed the SPARQL Query Language. SPARQL defines queries in terms of graph patterns that are matched against the directed graph representing the RDF data. SPARQL contains capabilities for querying required and optional graph patterns along with their conjunctions and disjunctions. The result of the match can also be used to construct new RDF graphs using separate graph patterns.

The Semantic Web is a Web of data. There is a lot of data we all use every day, and it's not part of the Web. For example, I can see my bank statements on the web, and my photographs, and I can see my appointments in a calendar. But can I see my photos in a calendar to see what I was doing when I took them? Can I see bank statement lines in a calendar? Why not? Because we don't have a web of data. Because data is controlled by applications, and each application keeps it to itself.

In order to achieve the goals described above, the most important is to be able to define and describe the relations among data (i.e., resources) on the Web. This is not unlike the usage of hyperlinks on the current Web that connect the current page with another one: the hyperlinks defines a relationship between the current page and the target. One major difference is that, on the Semantic Web, such relationships can be established between any two resources, there is no notion of current page. Another major difference is that the relationship (i.e, the link) itself is named, whereas the link used by a human on the (traditional) Web is not and their role is deduced by the human reader. The definition of those relations allow for a better and automatic interchange of data. RDF, which is one of the fundamental building blocks of the Semantic Web, gives a formal definition for that interchange.

★ XFN on the GRDDL
★ GRDDL specification updated works with Microformats

It is difficult to predict what a killer application is for a specific technology, and the prediction is often erroneous. That said, the integration of currently unbound and independent silos of data in a coherent application is certainly a good candidate. Specific examples are currently explored in areas like Health Care and Life Sciences, Public Administration, Engineering, etc.

Not necessarily, at least not directly. The Semantic Web technologies may act behind the scenes, resulting in a better user experience, rather than directly influencing the look on the browser.

Both formalisms have their strengths and weaknesses; their area of usage is different. The two data models serve different constituencies and the choice really depends on the application. There is no better or worse; only different.

he Semantic Web is about a web of data. The data itself can reside in databases, spreadsheets, Wiki pages, or indeed traditional web pages. The challenge is to develop tools that can export these data into RDF form: RDF plays the role of a common model, as a kind of a glue to integrate the data. That does not mean that the data must be physically converted into RDF form and stored in, say, RDF/XML. Instead, automatic procedures, for example SQL to RDF converters for relational databases, GRDDL processors for XHTML files with microformats, RDFa, etc, can produce RDF data on-the-fly as an answer to, eg, queries.

Until recently, it was not possible to incorporate full RDF into XHTML without violating the validity of the resulting XHTML, except for the usage of the meta and the link elements in the header. The best solution was to store the RDF separately and use the URIs to refer to the XHTML page and the link element in the XHTML page to refer to the RDF content. This technique is often called an RDF autodiscovery link and is used by a number of tools already. However, this has changed with the newer developements of GRDDL and of RDFa. The GRDDL provides a bridge to the microformats approach while RDFa provides an XHTML1.1 module that gives the possibility to use virtually any RDF vocabulary as annotations of the XHTML content, yielding RDF data.

RDF was designed to provide a common way to describe information so it can be read and understood by computer applications.
RDF descriptions are not designed to be displayed on the web.

RDF documents are written in XML. The XML language used by RDF is called RDF/XML.
By using XML, RDF information can easily be exchanged between different types of computers using different types of operating systems and application languages.

RDF became a W3C Recommendation 10. February 2004.

A Resource is anything that can have a URI, such as: "http://www.globalguideline.com/rdf"

A Property is a Resource that has a name, such as "author" or "homepage".

★ RDF uses Web identifiers (URIs) to identify resources.
★ RDF describes resources with properties and property values.

A Property value is the value of a Property, such as "XYZ" or "http://www.globalguideline.com" (note that a property value can be another resource)

The main elements of RDF are the root element, <RDF>, and the <Description> element, which identifies a resource.

RDF is a standard model for data interchange on the Web. RDF has features that facilitate data merging even if the underlying schemas differ, and it specifically supports the evolution of schemas over time without requiring all the data consumers to be changed.

RDF Schema (Resource Description Framework Schema, variously abbreviated as RDFS, RDF(S), RDF-S, or RDF/S) is a set of classes with certain properties using the RDF extensible knowledge representation data model, providing basic elements for the description of ontologies, otherwise called RDF vocabularies, intended to structure RDF resources. These resources can be saved in a triplestore to reach them with the query language SPARQL.

The RDF language is a part of the W3C's Semantic Web Activity. W3C's "Semantic Web Vision" is a future where:
★ Web information has exact meaning
★ Computers can integrate information from the web
★ Web information can be understood and processed by computers

★ Describing time schedules for web events
★ Describing properties for shopping items, such as price and availability
★ Describing content for search engines
★ Describing electronic libraries
★ Describing information about web pages (content, author, created and modified date)
★ Describing content and rating for web pictures

★ RDF stands for Resource Description Framework
★ RDF is a framework for describing resources on the web
★ RDF is designed to be read and understood by computers
★ RDF is not designed for being displayed to people
★ RDF is written in XML
★ RDF is a part of the W3C's Semantic Web Activity
★ RDF is a W3C Recommendation