CLI tools to validate, convert or query RDF files and SPARQL.
The functionality is provided by RDFLib, and while that provides a set of commands, those provided here are somewhat more extensive and also based upon a common command framework that can be extended easily for more cases.
Python developers will know other ways,
but for the (more) laymen -
as long as you have git and pipx installed -
you can install like so (on Linux and Mac):
mkdir -p ~/src
cd ~/src
git clone "https://github.com/johnstonskj/rdftools.git"
cd rdftools
pipx install .The tooling uses a common starting command - rdf -
that then executes sub-commands.
As expected, the command has a help function
and lists the supported sub-commands as positional arguments.
These sub-commands also have their own help.
$ rdf -h
usage: rdf [-h] [-v] {validate,convert,select,query} ...
RDF tool
positional arguments:
{validate,convert,select,shell,query}
subargs
optional arguments:
-h, --help show this help message and exit
-v, --verboseThe currently supported sub-commands are as follows.
convert- convert files between different RDF representations (NTriples, Notation3, RDF-XML, ...).query- execute SPARQL queries over RDF files.select- simple projections from RDF files.shell- run an interactive shell session.validate- validate an RDF file.
An example, running a SPARQL query over a downloaded file:
$ rdf query \
-i ~/social.n3 \
-r n3 \
-q "SELECT DISTINCT ?person ?topic
WHERE {
?person <http://example.org/social/relationship/1.0/likes>
?topic.
}"
person topic
============================================== =============================================
http://amazon.com/cprm/customers/1.0/Alice http://amazon.com/cprm/entities/1.0/Diving
http://amazon.com/cprm/customers/1.0/Bob http://amazon.com/cprm/entities/1.0/Diving
http://amazon.com/cprm/customers/1.0/Alice http://amazon.com/cprm/entities/1.0/Shoes
3 rows returned in 1.629622 seconds.The -v parameter to either rdf or one of the sub-commands
controls the standard Python logging level.
It can be stated multiple times,
to increase the logging verbosity;
-v for warnings,
-vv for informational,
-vvv for debug.
For a more interactive exploration of RDF data,
you can run rdf shell,
which gives you access to a lot of the same functions
as in the separate tools.
The shell has a single common graph
into which you can load data from external files
(and stores in the future),
and run SPARQL queries.
The shell also has a default initialization file,
so commonly used prefixes, common data, etc.
can be loaded before you start your session.
$ rdf shell
RDF Shell, v0.1.0.
reading commands from file /Users/simonjo/.rdfshrc
Graph updated with 40 statements.
>As you might expect,
the shell supports a help function and command completion,
as well as a persistent history.
The default location for this is ~/.rdfshrc;
all commands are read as if you typed them into the shell.
The default location for this is ~/.rdfsh_hist;
it will be read at startup and updated on closing the shell.
New commands are added as modules in the rdftools/scripts folder
and have the following structure.
import rdftools
def main():
(LOG, cmd) = rdftools.startup('Tool description.', add_args=None)
...The add_args parameter is used
to add additional command-line arguments to the common argparse structure.
The function, if required, takes in a parser object and returns it.
The common command line arguments include verbosity, help, and reading files.
def add_args(parser):
return parserThe results from startup are a standard logger
and an (ArgumentParser) Namespace object.
The tool can then use the functions:
read, read_into, read_all, write, and query
to perform common operations on RDF files.
Extending the shell is also pretty simple.
You add a function of the following form -
it always takes a context object first -
and the doc string will be used by default
as the displayed help for your command.
Arguments may be parsed for more structure,
and print() is used extensively for user feedback.
Note that you must always return the context,
whether you updated it or not.
The add_command function will install it into the shell,
enabling help and command completion.
def echo(context, args):
""" echo text
Echo back the following text."""
print(args)
return context
add_command(echo)