Journal 2 – RDF and Linked Open Data

In the morning today we talked about RDF and how its data is composed. RDF is about sharing and exchanging information, but not necessarily about sharing the tools to interpret the information. RDF can be like NoSQL in that it’s flexible, just add more properties. When the project becomes more mature though, things needs to be locked down and standardized. Eventually, the information about “blank node” connections would need to be published so that all connections can be clear outside the project.

An informal graph of sample triples by W3C:

In the afternoon we worked with markers and construction paper, laying out a physical example of the materials we could work with. In our case this was ancient pottery, and also the variables or attributes of possible pottery fragments. We had a specialist in our group, an academic that works with ancient Mediterranean pottery fragments, and she was able to give us a wide variety of attributes. Each fragment of pottery has multiple data points, such as shape, type, place found, date of creation, and type of glaze. Each of these attributes requires a further deconstruction, such as place, requiring both a name as a string value or text, and also a latitude and longitude value that’s numeric and geographical. RDF information needs to be very granular and specific. For example, not just a dollar amount for price, but two specifications — the dollar amount field would be a number reference, and also a currency reference that would point to a web-hosted ontology.

The value of “glaze” would point to an additional table containing information such as the elemental makeup and the percentage of each element contained within the fragment. It’s possible to use the RDF triple (subject<-->predicate<-->object) of glaze<-->element<-->percentage, but this would not necessarily be machine readable. People could understand that the percentage was a feature of the element, but machines/computers might get stuck at the element value. It’s not certain that machines would read an element and then also look for a percentage, most often the machine reading would stop at the element itself. If a blank node was used, perhaps titled “has components,” then this blank node could point to both the element and the value. This would relate the element and the percentage together without requiring one value to be privileged over the other. Using the title of “has components” would also make this blank node understandable for people.

Our RDF Graph for the term "glaze." On the left of "glaze" is the blank node with the name "has components."
Our RDF Graph for the term “glaze.” On the left of “glaze” is the blank node with the name “has components.”