LOD - Linked Open Data

In particular, the Linked Data shift is based on (1) using Universal Resource Identifiers (URIs) for identifying all kinds of “things”, (2) making these URIs accessible via the HTTP protocol and (3) providing a description of these things in the Resource Description Format (RDF) along with (4) URI links to related information (see Tim Berners-Lee’s Linked Data design principles http://www.w3.org/DesignIssues/LinkedData.html).

RDF is a formalism for representing information (very close to natural language) in triple statements consisting of a subject, predicate and object, where again each of them can be a URI (or an atomic value in the case of object). As a result, the World Wide Web of documents/intranets/things is complimented with a Web of Linked Data, where everybody can publish, interlink and enrich data. This Linked Data Web has some interesting characteristics:

• URIs serve two purposes: identifying "things" and serving as locators and access paths for information about these "things".
• Since everybody can coin their own URIs by simply using the address of some webspace under their control, the Web of Linked Data is as distributed and democratic as the Web itself.
• Identifiers defined by different people or organizations can be mixed and meshed.
• Linked Data published in various locations can be easily integrated by merging the sets of RDF triple statements thus dramatically simplifying data integration using special purpose links as defined in semantic web languages such as XFN, Microformats, OWL, Schema.org., DublinCore, etc.
• The same triple statement formalism is used for defining structure and data, thus overcoming the strict separation found in relational or XML databases.

Linked Data management goes beyond the classic data management approaches that assume complete control over schema and data. In the Web that is distributed and open, users and applications do not have control over the data. For this reason, the Linked Data lifecycle was introduced that involves issues such as (a) data extraction from unstructured or semi-structured sources and representing them in the RDF data model (b) storage and querying of data (c) manual revision and authoring (d) interlinking and fusing of related data in order to enable data integration across highly heterogeneous sources (e) classification and enrichment with additional upper level structures such as ontologies and rich vocabularies (f) quality analysis (g) evolution and repair and (h) search/browsing and exploration [1]. The LOD2 project (http://lod2.eu) has created a comprehensive stack of tools for supporting these different aspects of Linked Data management [2].

Refererences

1. https://joinup.ec.europa.eu/sites/default/files/D4.3.2_Case_Study_Linked_Data_eGov.pdf
2. [2] S. Auer et al.: “Managing the life-cycle of Linked Data with the LOD2 Stack” in proc. of ISWC 2012, http://iswc2012.semanticweb.org/sites/default/files/76500001.pdf

Linked Open Data - Introduction to the Special Theme, http://ercim-news.ercim.eu/en96/special/intro