Writing ontologies

Writers 

Similarly to reading, Cowl can write ontologies to files, buffers or custom output streams (see UOStream) through the CowlManager object. You can control which writer is used in a number of ways:

At compile-time: writers included in the compiled library can be selected by setting the COWL_WRITERS CMake variable. Built-in writers are exposed through cowl_writer_*() functions.
At run-time, globally: you can set the default writer by calling cowl_set_writer().
At run-time, locally: you can specify which writer you want CowlManager to use via cowl_manager_set_writer().

Additional writers can be integrated by providing suitably populated CowlWriter instances. Refer to the built-in writers if you need guidance.

struct CowlWriter

Defines a writer.

Public Members

char const *name: Name of the writer.

cowl_ret (*write_ontology)(UOStream *stream, CowlOntology *ontology)

Pointer to a function that writes an ontology to an output stream.

Note

This member is mandatory.

Param stream:: Output stream.
Param ontology:: Ontology.
Return:: Return code.

cowl_ret (*write)(UOStream *stream, CowlAny *object)

Pointer to a function that writes an object to an output stream.

Note

This member is optional.

Param stream:: Output stream.
Param object:: Object to write.
Return:: Return code.

CowlStreamWriter stream: Contains the streaming implementation of this writer.

Note

This member is optional.

CowlWriter cowl_writer_functional(void)

Returns the functional syntax writer.

Returns:: Functional syntax writer.

cowl_ret cowl_write(UOStream *stream, CowlAny *object)

Writes an object to the specified stream via the default writer.

Note

If no default writer is set, falls back to cowl_write_debug().

Parameters:

stream – Output stream.
object – Object.

Returns:

Return code.

ustream_ret cowl_write_debug(UOStream *stream, CowlAny *object)

Writes a debug representation of an object to the specified output stream.

Parameters:

stream – Output stream.
object – Object.

Returns:

Return code.

ustream_ret cowl_write_string(UOStream *stream, CowlString *string)

Writes a string to the specified output stream.

Parameters:

stream – Output stream.
string – String.

Returns:

Return code.

ustream_ret cowl_write_iri(UOStream *stream, CowlIRI *iri)

Writes an IRI to the specified output stream.

Parameters:

stream – Output stream.
iri – IRI.

Returns:

Return code.

ustream_ret cowl_write_object_type(UOStream *stream, CowlObjectType type)

Writes the object type to the specified output stream.

Parameters:

stream – Output stream.
type – Object type.

Returns:

Return code.

ustream_ret cowl_write_uint(UOStream *stream, ulib_uint uint)

Writes an unsigned integer to the specified output stream.

Parameters:

stream – Output stream.
uint – Unsigned integer.

Returns:

Return code.

ustream_ret cowl_write_error(UOStream *stream, CowlError const *error)

Writes an human readable representation of an error to the specified output stream.

Parameters:

stream – Output stream.
error – Error.

Returns:

Return code.

ustream_ret cowl_write_ustring(UOStream *stream, UString const *string)

Writes a string to the specified output stream.

Parameters:

stream – Output stream.
string – String.

Returns:

Return code.

ustream_ret cowl_write_cstring(UOStream *stream, char const *string)

Writes a string to the specified output stream.

Parameters:

stream – Output stream.
string – String.

Returns:

Return code.

cowl_write_static(stream, string)

Writes a string literal to the specified output stream.

Parameters:

stream – UOStream * Output stream.
string – char const [] String literal.

Returns:

ustream_ret Return code.

Writing ontologies as axiom streams 

All standard OWL serialization formats allow ontologies to be serialized in such a way that the resulting byte sequence consist of a header, a sequence of axioms, and a closing footer. Ontology documents can therefore be serialized in a streaming fashion, without first building an intermediate data store such as CowlOntology. This greatly reduces memory usage in cases where one needs to provide the OWL representation of some dynamic data.

To do so, the chosen writer must implement the CowlStreamWriter interface, and the ontology document must be serialized via the CowlOStream API. Similarly to input streams, you can retrieve a CowlOStream instance via cowl_manager_get_ostream().

struct CowlStreamWriter

Defines functions that must be implemented by stream writers.

Public Members

cowl_ret (*write_header)(UOStream *stream, CowlSymTable *st, CowlOntologyHeader header)

Pointer to a function that writes an ontology header to an output stream.

Param stream:: Output stream.
Param st:: Symbol table.
Param header:: Ontology header.
Return:: Return code.

cowl_ret (*write_axiom)(UOStream *stream, CowlSymTable *st, CowlAnyAxiom *axiom)

Pointer to a function that writes an axiom to an output stream.

Param stream:: Output stream.
Param st:: Symbol table.
Param axiom:: Axiom.
Return:: Return code.

cowl_ret (*write_footer)(UOStream *stream, CowlSymTable *st)

Pointer to a function that writes the ontology footer to an output stream.

Param stream:: Output stream.
Param st:: Symbol table.
Return:: Return code.

struct CowlOStream

Ontology output stream.

A lightweight way to serialize knowledge without creating CowlOntology objects.

Pseudo-extends: CowlObject

Writing ontologies

Writers

Writing ontologies as axiom streams

Writers 

Writing ontologies as axiom streams 