NAME

RDF::Core - An object oriented Perl module to support RDF.

RELEASE NOTE

RDF::Core is a pure perl implementation of RDF storage, parser and serializer. The storage's functionality is basic - store, delete, query statements, where query means ask about existence or count or retrieve statements conforming given mask of (subject, predicate, object). Three storages are available - in memory, file (DB_File) and DBMS (PostgreSQL). The parser supports full RDF/XML syntax including aboutEach attribute. The serializer tries to preserve anonymous nodes and to compact xml a bit by grouping statements with common subject.

Besides the basic querying, there is a query language implemented. The query language is focused on resource, not statement and the typical pattern is me->neighbor->child->age to express neighbour's children's age, not (me,neighbour, him) && (him, child, it) && (it, age, value). It contains some shortcuts to express things, that are (possibly) expressed often, like object->rdf:type = someClass. Functions are another enhancement of the language. They can be used instead of resource or property. Functions are implemented in a separated library, so that it's easy to create new or modify existing ones.

We focus on acceptable and clean interface between parts of the module. Typically a storage should have it's interface on a 'statement level' (add statement, get statement) rather then on data elements level (add this value into hash_one and that into hash_two), which comes with interface based on lower level base.

MODULES

RDF::Core includes the following modules. See documentation for particular modules for details:

RDF::Core::Model
Model provides interface to store RDF statements, ask about them (in a very simple manner yet) and retrieve them back.
- RDF::Core::Model::Parser
  Model::Parser is a simple interface object to a parser. It's purpose is to provide a prototype of object accomodating any other parser.
- RDF::Core::Model::Serializer
  Model::Serializer is an interface object for serializer.
RDF::Core::ModelSet
An RDF model set.
RDF::Core::Parser
Generates statements from an RDF XML document.
RDF::Core::Schema
The RDF Schema access.
RDF::Core::Serializer
Serializes RDF Model into XML.
RDF::Core::Storage
An object for storing statements. There are several implementations of Storage - in memory, in a BerkeleyDB 1.x (DB_File) files and PostgreSQL database.
- RDF::Core::Storage::DB_File
  Berkeley DB 1.x implementation of RDF::Core::Storage.
- RDF::Core::Storage::Memory
  An in-memory implementation of RDF::Core::Storage.
- RDF::Core::Storage::Postgres
  PostgreSQL implementation of RDF::Core::Storage.
RDF::Core::Enumerator
Enumerator is a result set of statements retrieved from Model
- RDF::Core::Enumerator::DB_File
  Enumerator that can be used with the DB_File storage.
- RDF::Core::Enumerator::Memory
  Enumerator that can be used with the Memory storage.
- RDF::Core::Enumerator::Postgres
  Enumerator that can be used with the PostgreSQL storage.
RDF::Core::Query
Implementation of query language
RDF::Core::Evaluator
Evaluator gets a query object that RDF::Core::Query parsed and evaluates the query.
RDF::Core::Function
A package of functions for query language.
Basic elements
- RDF::Core::NodeFactory
  Produces literals and resources, generates URI for anonymous resources.
- RDF::Core::Node
  An ancestor of RDF::Core::Resource and RDF::Core::Literal.
- RDF::Core::Resource
  A resource for RDF statement.
- RDF::Core::Literal
  A literal value for RDF statement.
- RDF::Core::Statement
  An RDF statement.

LICENSE

This package is subject to the MPL (or the GPL alternatively).

AUTHOR

Ginger Alliance, rdf@gingerall.cz