Every programmer must understand the methods available to retrieve data from each API, and write custom code for accessing data from each data source. A triple mirrors the basic structure of a simple sentence, such as this one:. Factors that may be persuasive in such situations are the value of the new data set i. As the graphs are identified with URI references, it is possible to talk about them in RDF, for instance, by adding triples to the graph itself which describe the creator or the retrieval date of the graph. This chapter will discuss the primary design considerations that must be taken into account when preparing data to be published as Linked Data on the Web, before introducing specific publishing recipes in Chapter 5. If very specific or proprietary terms are used for linking, they should be linked to more generic terms using rdfs: The checklist below can be used by Linked Data publishers to verify that data meets the key requirements.
Where structured data exists in queryable form behind a custom API such as the Flickr or Amazon Web APIs, or a local application or operating system API , the situation is a little more complex, as a custom wrapper will likely need to be developed according to the specifics of the API in question. Consequently, data returned from Web APIs typically exists as isolated fragments, lacking reliable onward links signposting the way to related data. As is often the case, there are no hard and fast rules regarding this issue, and each data publisher should consider the specifics of their publication scenario and the potential consumption patterns of the data. Increasing numbers of data providers and application developers have adopted Linked Data. In this case, the goal of using RDF was not to expose Linked Data for consumption by third parties, but to aid internal content management and data integration in a domain with high levels of connectivity between players, teams, fixtures and stadia. The Web of Data can be seen as an additional layer that is tightly interwoven with the classic document Web and has many of the same properties:. These statements of relationships between things are, in essence, links connecting things in the world.
However, the syntax is also viewed as difficult for humans to read and write, and, therefore, consideration should be given to using other serializations in data management and curation workflows that involve human intervention, and to the provision of alternative serializations for consumers who jennifer jentzsch thesis wish to eyeball the data.
Later, they, or somebody else, may invest effort into finding and publishing owl: The factors that determine the jennifer jentzsch thesis for a specific pattern are:.
Linked Data: Evolving the Web into a Global Data Space
In an open environment like the Web it is likely that Jeff is not the only one talking jennifer jentzsch thesis the place or the famous person, but that there are many different information providers who talk about the same entities. The following sections describe these tasks outlined above in more detail, and they refer to relevant papers and open-source tools that can be used to perform the tasks.
One school of thought says that each RDF description of a resource should convey the same informational content as its corresponding HTML page or contain enough data such that applications consuming the RDF description do not also have to request the descriptions of all resources referenced in the description before they can jennifer jentzsch thesis displaying information to the user.
These were complemented by user-generated content sites that were built with native support for Linked Data, such as Revyu. This chapter will discuss the primary design considerations that must be taken into account when preparing data to be published as Linked Data on the Jennifer jentzsch thesis, before introducing specific publishing recipes in Chapter 5.
Far jennifer jentzsch thesis being an additional layer on top of but separate from the Web, Linked Data is just another warp or weft being steadily interwoven with the fabric of the Web. There are two different strategies to make URIs that identify real-world objects dereferenceable. The following section presents a checklist that can be used to validate that a data set complies with the various Linked Data best practices.
In cases jennifer jentzsch thesis no common identifiers exist across data sets, it is necessary to employ more complex similarity-based linkage heuristics. On the other hand, the Web of Data tries to deal with heterogeneity by making data as self-descriptive as possible.
In common with data volume, the rate of jennifer jentzsch thesis in your data set will affect the publishing pattern you choose. In such cases the data publisher must exercise judgement in publishing those incoming links that jennifer jentzsch thesis be most useful to data consumers. This allows these names to be looked up using any client, such as a Web browser, that speaks the HTTP protocol. The Linking Open Drug Data  initiative represents a hybrid scenario, where Linked Data is enabling commercial organizations to connect and integrate data they are willing to share with each other for the purposes of collaboration.
Linked Data: Evolving the Web into a Global Data Space
Data is published as CSV data dumps, Excel spreadsheets, and in a multitude of domain-specific data formats. This section will explore these issues in detail.
Just as hyperlinks in the classic Web connect documents into a single global information space, Linked Data uses hyperlinks to connect disparate data into a single global data space. As the graphs are identified with URI references, it is possible to talk about them in RDF, for instance, by adding triples to the graph itself which jennifer jentzsch thesis the creator or the retrieval date of the graph.
This is easily achieved using a scripting language such as PHP. Such external RDF links are fundamental for the Web of Data as they are the glue that connects data islands into a global, interconnected data space and jennifer jentzsch thesis they enable applications to discover additional data sources in a follow-your-nose fashion.
In order to provide a forum and to coordinate the efforts to increase the global interoperability jennifer jentzsch thesis library data, W3C has started a Library Linked Data Incubator Group Jennifer jentzsch thesis Data versions of the EuroStat 28World Factbook 29 and US Census 30 data sets begin to bridge the worlds of statistics, politics and social jennifer jentzsch thesis, while Ordnance Survey the national mapping agency of Great Britain has begun to publish Linked Data describing the administrative areas within the Great Britain 31in efforts related to the data.
The HTML specification defines the anchor element, aone of the valid attributes of which is the href. An RDF resource is declared to be a class by typing it as an instance of rdfs: Jennifer jentzsch thesis such cases it is generally advisable to retain the existing data management infrastructure and software, so as not to disrupt legacy applications, and instead simply publish a Linked Data view of the relational database. Consequently, any license based on copyright, such as the Creative Commons licenses, is inapplicable to factual data.
A task related to link generation is the maintenance of links over time as data sources change.
Making this data easily accessible enables organisations and members of the public to work with the data, analyse it to discover new insights, and build tools that help communicate these findings to others, thereby helping citizens make informed choices and hold public servants to account. SKOS is a vocabulary for expressing conceptual hierarchies, often referred to as taxonomies, while RDFS and OWL provide vocabularies for describing conceptual models in terms of classes and their properties.
Just as traditional Web browsers allow users to navigate between HTML pages by following hypertext links, Linked Data browsers allow users to jennifer jentzsch thesis between data sources by following RDF links.
This translation can rely on vocabulary links, such as owl: Both should be able to retrieve representations of resources in a form that meets their needs, such as Jennifer jentzsch thesis for humans and RDF for machines. Chapter 3 describes some of the wide variety of data sets already available on the Web of Data, which collectively provide many potential targets for links from within a new data set.
Two primary mechanisms jennifer jentzsch thesis available for publishing descriptions of a data set: