From the command line
1 Retrieving ontology modules
The PLM-RDL ontologies can be downloaded to local files. Specifying which format you will accept makes use of content negotiation; for a friendly introduction, see Bob DuCharme’s 2011 blog post “Quick and dirty linked data content negotiation". The following commonly used tools work well for downloads.
Choose one of these file formats (cf. downloads for details):
For example, here is how to download the ISO 15926-14 OWL 2 ontology
in Turtle format, into a file named
lis14.ttl. We request the format
- Download using
- specify the filename with
wget --header="Accept: text/turtle" http://rds.posccaesar.org/ontology/lis14/ont/core --output-document=lis14.ttl
- Download using
>to redirect the retrieved data to a file.
curl --header "Accept: text/turtle" -L http://rds.posccaesar.org/ontology/lis14/ont/core > lis14.ttl
2 If you get a “not trusted” response
It is common for companies to protect their networks with services that filter traffic. This will in some cases block the download of PCA ontologies, and you will see messages like the following.
ERROR: The certificate of ‘rds.posccaesar.org’ is not trusted. ERROR: The certificate of ‘rds.posccaesar.org’ doesn't have a known issuer.
curl: (60) SSL certificate problem: unable to get local issuer certificate
The workaround is to instruct
curl to trust the
rds.posccaesar.org website anyway, with the following command-line
That is, the commands shown in the previous section need to be given as follows.
wget --no-check-certificate --header="Accept: text/turtle" http://rds.posccaesar.org/ontology/lis14/ont/core --output-document=lis14.ttl curl --insecure --header "Accept: text/turtle" -L http://rds.posccaesar.org/ontology/lis14/ont/core > lis14.ttl
3 Retrieving single resources
Thanks to the Linked Data service on this website, each entity in the RDL can be downloaded separately, by requesting its resource URI. Here are two examples (both apply the “insecure certificate” workaround of the previous section). We download the description of the RDL class Compressor, which has the URI https://rds.posccaesar.org/ontology/plm/rdl/PCA_100001002.
wget, download the RDF/XML description of Compressor to local file
wget --header="Accept: application/rdf+xml" https://rds.posccaesar.org/ontology/plm/rdl/PCA_100001002 --no-check-certificate --output-document compressor.xml
curl, download the JSON-LD description of Compressor to local file
curl --header "Accept: application/ld+json" https://rds.posccaesar.org/ontology/plm/rdl/PCA_100001002 -L --insecure > compressor.jsonld
4 Example: Find the current version of an RDL ontology
The RDL ontologies have IRIs that don’t directly reflect the version
of the ontology. Instead, the OWL 2 annotation property
provides the version number (as per the recommendation).
The following command line can be used to find the current version IRI
for an ontology, by downloading the ontology with
extracting the version IRI with filters
curl -s -L --header "Accept: application/rdf+xml" --insecure \ http://rds.posccaesar.org/ontology/plm/ont/uom | sed 's/^ *//g' | grep -ie "owl:versioniri"