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) are currently not written.
-
A file named owlOntology, which contains annotation
information from the Ontology object in the Protege file.
-
A file named owlImports, which contains an
Ontology object that imports all the files that were split.
-
A directory named owldoc/, which contains OWL documentation for the
terms split from the owl file.
-
A copy of the file being split.
Ontology Authoring Guidelines
A SSWAP ontology is normally written by using the free
Protege ontology editor
and splitting the resulting OWL file using the tool on this page. After splitting
the file, the unmodified file itself is 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 ontology splitter tool,
the following guidelines should be observed in using Protege - the examples below
all use the ontology referred to in
map.owl:
-
The default namespace (i.e. the value of the "Ontology URI" field on Protege's
Metadata tab) of the ontology should be the URL at which the unsplit OWL 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
file, this URL is http://sswapmeet.sswap.info/map/map.owl.
-
Ironically, the default namespace 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 (make 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.
-
In summary, the Protege OWL file will have lines similar to the following:
<!-- note trailing / on directory for prefix -->
xmlns:map="http://sswapmeet.sswap.info/map/"
<!-- note trailing # on .owl file for default namespace -->
xmlns="http://sswapmeet.sswap.info/map/map.owl#"
<!-- note .owl file as base; no trailing # -->
xml:base="http://sswapmeet.sswap.info/map/map.owl"
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.
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