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Add RDF Triples

Source: R/rdf_add.R
rdf_add.Rd

add a triple (subject, predicate, object) to the RDF graph

Usage

rdf_add(
  rdf,
  subject,
  predicate,
  object,
  subjectType = as.character(NA),
  objectType = as.character(NA),
  datatype_uri = as.character(NA)
)

Arguments

rdf

an rdf object

subject

character string containing the subject

predicate

character string containing the predicate

object

character string containing the object

subjectType

the Node type of the subject, i.e. "uri", "blank"

objectType

the Node type of the object, i.e. "literal", "uri", "blank"

datatype_uri

the datatype URI to associate with a object literal value

Value

Silently returns the updated RDF graph (rdf object). Since the rdf object simply contains external pointers to the model object in C code, note that the input object is modified directly, so you need not assign the output of rdf_add() to anything.

Details

rdf_add() will automatically 'duck type' nodes (if looks like a duck...). That is, strings that look like URIs will be declared as URIs. (See URI). Predicate should always be a URI (e.g. URL or a prefix:string), cannot be blank or literal. Subjects that look like strings will be treated as Blank Nodes (i.e. will be prefixed with _:). An empty subject, "", will create a blank node with random name. Objects that look like URIs will be typed as resource nodes, otherwise as literals. An empty object "" will be treated as blank node. Set subjectType or objectType explicitly to override this behavior, e.g. to treat an object URI as a literal string. NAs are also treated as blank nodes in subject or object See examples for details.

References

https://en.wikipedia.org/wiki/Uniform_Resource_Identifier

Examples

rdf <- rdf()
rdf_add(rdf, 
    subject="http://www.dajobe.org/",
    predicate="http://purl.org/dc/elements/1.1/language",
    object="en")
    
## non-URI string in subject indicates a blank subject
## (prefixes to "_:b0")
rdf_add(rdf, "b0", "http://schema.org/jobTitle", "Professor") 

## identically a blank subject.  
## Note rdf is unchanged when we add the same triple twice.
rdf_add(rdf, "b0", "http://schema.org/jobTitle", "Professor", 
        subjectType = "blank") 
        
## blank node with empty string creates a default blank node id
rdf_add(rdf, "", "http://schema.org/jobTitle", "Professor")   
                    

## Subject and Object both recognized as URI resources:
rdf_add(rdf, 
        "https://orcid.org/0000-0002-1642-628X",
        "http://schema.org/homepage", 
        "http://carlboettiger.info")  

 ## Force object to be literal, not URI resource        
rdf_add(rdf, 
        "https://orcid.org/0000-0002-1642-628X",
        "http://schema.org/homepage", 
        "http://carlboettiger.info",
        objectType = "literal")