Data.RDF

The Core module exports all serializers and parsers, types, and query functions of the library.

Documentation

class RDF rdf where

An RDF value is a set of (unique) RDF triples, together with the operations defined upon them.

For information about the efficiency of the functions, see the documentation for the particular RDF instance.

For more information about the concept of an RDF graph, see the following: http://www.w3.org/TR/rdf-concepts/#section-rdf-graph.

Methods

baseUrl :: rdf -> Maybe BaseUrl

Return the base URL of this RDF, if any.

prefixMappings :: rdf -> PrefixMappings

Return the prefix mappings defined for this RDF, if any.

addPrefixMappings :: rdf -> PrefixMappings -> Bool -> rdf

Return an RDF with the specified prefix mappings merged with the existing mappings. If the Bool arg is True, then a new mapping for an existing prefix will replace the old mapping; otherwise, the new mapping is ignored.

empty :: rdf

Return an empty RDF.

mkRdf :: Triples -> Maybe BaseUrl -> PrefixMappings -> rdf

Return a RDF containing all the given triples. Handling of duplicates in the input depend on the particular RDF implementation.

triplesOf :: rdf -> Triples

Return all triples in the RDF, as a list.

Note that this function returns a list of triples in the RDF as they were added, without removing duplicates and without expanding namespaces.

uniqTriplesOf :: rdf -> Triples

Return unique triples in the RDF, as a list.

This function performs namespace expansion and removal of duplicates.

select :: rdf -> NodeSelector -> NodeSelector -> NodeSelector -> Triples

Select the triples in the RDF that match the given selectors.

The three NodeSelector parameters are optional functions that match the respective subject, predicate, and object of a triple. The triples returned are those in the given graph for which the first selector returns true when called on the subject, the second selector returns true when called on the predicate, and the third selector returns true when called on the ojbect. A Nothing parameter is equivalent to a function that always returns true for the appropriate node; but implementations may be able to much more efficiently answer a select that involves a Nothing parameter rather than an (id True) parameter.

The following call illustrates the use of select, and would result in the selection of all and only the triples that have a blank node as subject and a literal node as object:

select gr (Just isBNode) Nothing (Just isLNode)

Note: this function may be very slow; see the documentation for the particular RDF implementation for more information.

query :: rdf -> Maybe Node -> Maybe Node -> Maybe Node -> Triples

Return the triples in the RDF that match the given pattern, where the pattern (3 Maybe Node parameters) is interpreted as a triple pattern.

The Maybe Node params are interpreted as the subject, predicate, and object of a triple, respectively. Just n is true iff the triple has a node equal to n in the appropriate location; Nothing is always true, regardless of the node in the appropriate location.

For example, query rdf (Just n1) Nothing (Just n2) would return all and only the triples that have n1 as subject and n2 as object, regardless of the predicate of the triple.

Instances

RDF TriplesGraph

RDF MGraph

RDF PatriciaTreeGraph

class RdfSerializer s where

An RdfSerializer is a serializer of RDF to some particular output format, such as NTriples or Turtle.

Methods

hWriteRdf :: forall rdf. RDF rdf => s -> Handle -> rdf -> IO ()

Write the RDF to a file handle using whatever configuration is specified by the first argument.

writeRdf :: forall rdf. RDF rdf => s -> rdf -> IO ()

Write the RDF to stdout; equivalent to hWriteRdf stdout.

hWriteH :: forall rdf. RDF rdf => s -> Handle -> rdf -> IO ()

Write to the file handle whatever header information is required based on the output format. For example, if serializing to Turtle, this method would write the necessary @prefix declarations and possibly a @baseUrl declaration, whereas for NTriples, there is no header section at all, so this would be a no-op.

writeH :: forall rdf. RDF rdf => s -> rdf -> IO ()

Write header information to stdout; equivalent to hWriteRdf stdout.

hWriteTs :: s -> Handle -> Triples -> IO ()

Write some triples to a file handle using whatever configuration is specified by the first argument.

WARNING: if the serialization format has header-level information that should be output (e.g., @prefix declarations for Turtle), then you should use hWriteG instead of this method unless you're sure this is safe to use, since otherwise the resultant document will be missing the header information and will not be valid.

writeTs :: s -> Triples -> IO ()

Write some triples to stdout; equivalent to hWriteTs stdout.

hWriteT :: s -> Handle -> Triple -> IO ()

Write a single triple to the file handle using whatever configuration is specified by the first argument. The same WARNING applies as to hWriteTs.

writeT :: s -> Triple -> IO ()

Write a single triple to stdout; equivalent to hWriteT stdout.

hWriteN :: s -> Handle -> Node -> IO ()

Write a single node to the file handle using whatever configuration is specified by the first argument. The same WARNING applies as to hWriteTs.

writeN :: s -> Node -> IO ()

Write a single node to sdout; equivalent to hWriteN stdout.

Instances

RdfSerializer NTriplesSerializer

RdfSerializer TurtleSerializer

class RdfParser p where

An RdfParser is a parser that knows how to parse 1 format of RDF and can parse an RDF document of that type from a string, a file, or a URL. Required configuration options will vary from instance to instance.

Methods

parseString :: forall rdf. RDF rdf => p -> Text -> Either ParseFailure rdf

Parse RDF from the given text, yielding a failure with error message or the resultant RDF.

parseFile :: forall rdf. RDF rdf => p -> String -> IO (Either ParseFailure rdf)

Parse RDF from the local file with the given path, yielding a failure with error message or the resultant RDF in the IO monad.

parseURL :: forall rdf. RDF rdf => p -> String -> IO (Either ParseFailure rdf)

Parse RDF from the remote file with the given HTTP URL (https is not supported), yielding a failure with error message or the resultant graph in the IO monad.

Instances

RdfParser NTriplesParser

NTriplesParser is an instance of RdfParser.

RdfParser TurtleParser

TurtleParser is an instance of RdfParser.

RdfParser XmlParser

XmlParser is an instance of RdfParser.

Export types and query functions

module Data.RDF.Types

module Data.RDF.Query

Export RDF type class instances

module Data.RDF.TriplesGraph

module Data.RDF.MGraph

module Data.RDF.PatriciaTreeGraph

Export RDF parsers and serializers

module Text.RDF.RDF4H.NTriplesSerializer

module Text.RDF.RDF4H.NTriplesParser

module Text.RDF.RDF4H.TurtleSerializer

module Text.RDF.RDF4H.TurtleParser

module Text.RDF.RDF4H.XmlParser