This tool splits an OWL ontology, written using
Protege,
into multiple files. The tool requires that the OWL file that comprises the
ontology conform to the guidelines outlined below.
The file is split into the following files that conform to the SSWAP protocol,
and packaged into a single zip archive:
A file for each OWL Class, ObjectProperty, DatatypeProperty, or AnnotationProperty
that is in the namespace associated with a user-supplied namespace prefix.
For example, the prefix map represents the namespace
http://sswapmeet.sswap.info/map/ in the
map.owl
file, so splitting that file would yield files for the classes
map:MapSet,
map:MapPosition,
etc. Note that files for individuals (as opposed to classes or predicates) are not written.
A file named owlOntology, which contains annotation
information from the ontology in the
Protege file.
A file named owlImports, which contains an
owl:Ontology resource that imports all the files that were split.
A copy of the file being split.
Optional Prefix Or URI:
Optional Prefix Or URI:
Optional Prefix Or URI:
Ontology Authoring Guidelines
A SSWAP ontology may be written by using the free
Protege ontology
editor and splitting the resulting OWL file using the tool on this page.
The OWL Ontology Splitter is OWL 1.1 compliant. After splitting the file,
the unmodified file itself should be hosted along with the files generated
by the splitter (a copy of the file is included in the zip file). This
enables others to reference your ontology from within
Protege by
importing your OWL file at its URL. To get
Protege to
build a file suitable for use by the OWL Ontology Splitter, the following
guidelines should be observed in using
Protege 3.4 - the examples below use the ontology referred
to in map.owl:
The Ontology URI (i.e., the value of the "Ontology URI" field on
Protege's
Metadata tab of the ontology should be the URI at which the monolithic unsplit ontology
file is to reside. Note that even though the RDF/XML will appear in the OWL file as
<owl:Ontology rdf:about=""/>, this default namespace will be
displayed in Protege
as the absolute URL of the OWL file, and this absolute URL
is what you should enter in this field. In the example of the
map.owl
ontology, this URL is http://sswapmeet.sswap.info/map/map.owl.
Ironically, the Ontology URI discussed above should not be used in
defining ontology terms. Instead, you should define a named namespace that
refers to the parent path of the OWL file (be sure to include the trailing
slash [/] character) and create ontology terms in that namespace. In the example
of the map.owl
ontology file, this namespace is referenced using the
map prefix, which refers to the URL
http://sswapmeet.sswap.info/map/.
It is good practice to give your namespace prefixes names that you expect to
be unique - for example, a Gramene-specific map ontology could be given the
prefix grameneMap. Keeping namespaces unique enables
Protege
to honor your prefix names when it imports files; when prefix names
clash, it arbitrarily creates new, less intuitive prefixes.
If your ontology imports other ontologies, the OWL Ontology Splitter will preserve
those import directives into the owlOntology file. Yet in most cases this
type of lexical transfer of file names is not what is wanted: what is wanted is for
the new owlOntology file to import the "split versions" of ontologies, not
their old monolithic files. The OWL Ontology Splitter will replace importing any
file ending in *.owl with a file named <namespace>:owlImports. In this
manner you can continue to work with monolithic *.owl ontologies in a tool such as
Protege,
while still splitting the resultant ontology and maintaining owl:imports to
other split ontologies.
In summary, the Protege
OWL file (and Metadata tab) will have lines similar to the following:
<!-- note .owl file as base; no trailing #. This corresponds to the "Ontology URI" field -->
xml:base="http://sswapmeet.sswap.info/map/map.owl"
<!-- note trailing # on .owl file for default namespace. This corresponds to the "Default Namespace" field -->
xmlns="http://sswapmeet.sswap.info/map/map.owl#"
<!-- note trailing / on directory for prefix. This corresponds to the Prefix/Namespace fields -->
xmlns:map="http://sswapmeet.sswap.info/map/"
These authoring guidelines ensure that your terms are delineated by slashes (/), not hashes (#),
and thus translate immediately into independently dereferencable URIs: one URI per term as
generated by the OWL Ontology Splitter.
As a hands-on example, you can save
map.owl
to your desktop and open it in Protege
(in the "Welcome to Protege" dialog that
appears when you first open Protege,
click the "Open Other..." button to select
map.owl;
or, if Protege
is already started, select the File -> Open menu
item and click the "File" button to select
map.owl
from the resulting dialog).
Note that this file has a namespace prefix map
that refers to the namespace http://sswapmeet.sswap.info/map/.
In Protege,
you can view the contents of this file by selecting
"View RDF/XML source code..." from the Code menu.
After viewing map.owl
in Protege, split it by choosing
the path to the file in the File: field above, entering map in
the prefix field, and pressing the "Split File" button. Save the resulting
map.zip file to your desktop and unzip it to view its contents.
