Overview - NASA-PDS/product_relationships GitHub Wiki

Glossary

RDF - Resource Description Framework.
Turtle - Terse RDF Triple Language, a common data format for storing RDF data.
SPARQL (pronounced "sparkle") - RDF query language.

Data Model

The RDF data model is based on the idea of making statements about resources in the form of Subject-Predicate-Object, known as triples. For example,

Bennu is asteroid

More complex example in Turtle format,

PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
PREFIX pds: <pds:>

<urn:nasa:pds:context:investigation:mission.orex::1.1> pds:type "Mission".
<urn:nasa:pds:context:investigation:mission.orex::1.1> pds:name "OSIRIS-REx".
<urn:nasa:pds:context:investigation:mission.orex::1.1> pds:start_date "2016-09-08"^^xsd:date.
<urn:nasa:pds:context:investigation:mission.orex::1.1> pds:lid_ref <urn:nasa:pds:context:target:asteroid.101955_bennu>.

The same example in compact Turtle format,

<urn:nasa:pds:context:investigation:mission.orex::1.1> 
  pds:type "Mission";
  pds:name "OSIRIS-REx";
  pds:start_date "2016-09-08"^^xsd:date;
  pds:lid_ref <urn:nasa:pds:context:target:asteroid.101955_bennu>.

Note that Subject is a resource ID.

Graph Representation

RDF data model can be represented as a directed graph, where each Subject-Predicate-Object triple defines directed edge of the graph, StartVertex->Edge->EndVertex. StartVertex is always a resource ID. EndVertex can be either a resource ID or a constant (string, date, number, etc.).

For example,

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