What is linked data?

The fact that data comes in all sorts of shapes and sizes has already been blogged about, but what is the concern about adding data into online journals? after all, printed journals have included data in the shape of graphs or tables for a great many years. The problem is now that the journal article and its corresponding data is no longer in the flat two dimensional world of a piece of paper, but is part of the multi-dimensional world of the internet, the data is linked to something else. Linked data, according to Bizer, Heath and Berners-Lee (http;//linkeddatte.org/docs/ijwis-special-issue) is the method by which data is connected, structured and published on the web resulting in a “web of data”. Linked data “refers to data published on the web in such a way that it is machine readable, its meaning is is explicitly defined, it is linked to other external data sets and can in turn be linked to from external data sets”.

Before the data is published and linked, it has to be put somewhere. Most of our research participants said that they store their data in a personal storage system, either their own work or home computer, or on a portable storage device. While, of course, such spaces may be linked to the internet, it is rather like keeping the data in a filing cabinet, although anyone can go and find the data, they have to search very hard or ask the data keeper to give it to them. Data therefore has to be uploaded to a space that is openly accessible, which could be a university repository, a subject repository, a web page, or even onto the publishers own servers.

Again this is not as simple as it seems, first you have to choose your repository and ensure that it will accept your sort of data. Once safely held in a repository, the data must be permanently linked and archived. As digital repositories are relatively new things, there is the question of what if the repository you have chosen has to close? where will the data go? If the data is uploaded onto the publisher’s server, do they have the capacity to hold all the data for all the journals that they publish, as well as all the articles? Suddenly the storage needs of a single article can become top heavy. At the moment there are not very clear answers to these concerns, therefore there needs to be some guidelines and methods of best practice resolved before all data can be truly linked.

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Data comes in all sorts of shapes and sizes

The JoRD project has not set out to define the term “data” (or the singular form of the word, “datum”). This was a fortunate choice, because one of the messages that has clearly come across from all the participants of our study is that data can take many forms. The recent Royal Society Report, “Science as an Open Enterprise”, (http://royalsociety.org/uploadedFiles/Royal_Society_Content/policy/projects/sape/2012-06-20-SAOE.pdf) includes a glossary of data terms which illustrates the ways in which the term “data” can be used. For example:

• big data – data that requires massive computing power to process
• broad data – structured big data
• data set – a collection of  information held in electronic form
• linked data – data that has been allocated a unique identifying number to be able to access it from an electronic storage facility

… and those are just a few terms that it explains. The word “Data” is defined as “Qualitative  or  quantitative statement or numbers that are (or assumed to be ) factual”. The researchers that were part of this study considered that their data took more forms that just statements or numbers.

Researchers described the data that their research generated as:  software, video footage, geodata, geological maps, ontologies, web services and data models , as can be seen in the table below. The multitude of forms therefore makes it difficult for publishers to include in their on-line published articles. The publishers said that linked data in a journal article should be  “fit for use” and “replicable” and consider that data in many different formats is “Messy” and currently is not supplied with sufficient meta-data. Another consideration is the resulting file size of an article if the publisher saves the embedded data on their own servers. Data repositories and data centres are the more practical method of data storage with published articles incorporating linked data.

Therefore that is one reason for Journals to have a data policy, and a good argument for those policies to be collected and made accessible in a centralised resource, a JoRD Policy Bank  Service.

Researchers description of data	Qualitative(documents and text)	Quantitative(figures)	Visual data (images)	Virtual data (software or protocols)
Collection of examiner reports and questions supervisory reports, letters and other documentary evidence.	√
Dataset of measurements and statistical analyses		√
Digitised Textual Sources	√
Excavation, field observation, environmental monitoring, software to collate mine and analyse	√			√
Excel sheets		√
Focus Group, Interview Transcripts, some footage of people using computers, digital photographs	√		√
Geodata		√		√
Geologic maps, chemical and isotopic analyses of Earth Materials, GIS datasets		√	√	√
Interview transcripts	√
Ontologies				√
Reports	√
Visualization			√
Web Services, Data Models and Specifications				√