C++ implementation of the HDT compression format
Header Dictionary Triples (HDT) is a compression format for RDF data that can also be queried for Triple Patterns.
In order to compile this library, you need to have the following dependencies installed:
sudo apt install autoconfon Debian-based distros (e.g., Ubuntu)
sudo dnf install autoconfon Red Hat-based distros (e.g., Fedora)
brew install autoconfon macOS/OSX
sudo apt install libtoolon Debian-based distros (e.g., Ubuntu)
sudo dnf install libtoolon Red Hat-based distros (e.g., Fedora)
brew install libtoolon macOS/OSX
GNU zip (gzip) Allows GNU zipped RDF input files to be ingested, and allows GNU zipped HDT files to be loaded.
sudo apt install zlib1g zlib1g-devon Debian-based distros (e.g., Ubuntu)
sudo dnf install gzipon Red Hat-based distros (e.g., Fedora)
- zlib is already included as part of macOS/OSX
pkg-config A helper tool for compiling applications and libraries.
sudo apt install pkg-configon Debian-based distros (e.g., Ubuntu)
sudo dnf install pkgconf-pkg-configon Red Hat-based distros (e.g., Fedora)
brew install pkg-configon macOS/OSX
Serd v0.28+ The default parser that is used to process RDF input files. It supports the N-Quads, N-Triples, TriG, and Turtle serialization formats.
sudo apt install libserd-0-0 libserd-devon Debian-based distros (e.g., Ubuntu)
sudo dnf install serd serd-develon Red Hat-based distros (e.g., Fedora)
brew install serdon macOS/OSX
Sometimes the version of Serd that is distributed by package managers is too old. In that case, Serd can also be built manually: see https://github.com/drobilla/serd for the installation instructions.
To compile and install, run the following commands under the directory
hdt-cpp. This will also compile and install some handy tools.
./autogen.sh ./configure make -j2 sudo make install
Sometimes, the above instructions do not result in a working HDT installation. This section enumerates common issues and their workaround.
Compilation issues using Kyoto Cabinet
The support for Kyoto Cabinet was never finished and is currently suspended. It is for the time being not possible to compile HDT with KyotoCabinet.
In file included from src/dictionary/KyotoDictionary.cpp:38:0: src/dictionary/KyotoDictionary.hpp:108:18: error: conflicting return type specified for 'virtual unsigned int hdt::KyotoDictionary::getMapping()' unsigned int getMapping(); ^
Package requirements (serd-0 >= 0.28.0) were not met
Package requirements (serd-0 >= 0.28.0) were not met: Requested 'serd-0 >= 0.28.0' but version of Serd is 0.X
Serd is not 0.28+, probably because of the package manager. Built it manually at https://github.com/drobilla/serd.
./configure cannot find Serd
./configure you get a message similar to the
Package 'serd-0', required by 'virtual:world', not found
This means that
./configure cannot find the location of the
serd-0.pc file on your computer. You have to find this location
yourself, e.g., in the following way:
find /usr/ -name serd-0.pc
Once you have found the directory containing the
serd-0.pc file, you
have to inform the
./configure script about this location by setting
the following environment variable (where directory
/usr/local/lib/pkgconfig/ is adapted to your situation):
After compiling and installing, you can use the handy tools that are
hdt-cpp/libhdt/tools. We show some common tasks that can
be performed with these tools.
RDF-2-HDT: Creating an HDT
HDT files can only be created for standards-compliant RDF input files. If your input file is not standards-compliant RDF, it is not possible to create an HDT files out of it.
$ ./rdf2hdt data.nt data.hdt
HDT-2-RDF: Exporting an HDT
You can export an HDT file to an RDF file in one of the supported serialization formats (currently: N-Quads, N-Triples, TriG, and Turtle). The default serialization format for exporting is N-Triples.
$ ./hdt2rdf data.hdt data.nt
Querying for Triple Patterns
You can issue Triple Pattern (TP) queries in the terminal by
specifying a subject, predicate, and/or object term. The questions
?) denotes an uninstantiated term. For example, you can
retrieve all the triples by querying for the TP
? ? ?:
$ ./hdtSearch data.hdt >> ? ? ? http://example.org/uri3 http://example.org/predicate3 http://example.org/uri4 http://example.org/uri3 http://example.org/predicate3 http://example.org/uri5 http://example.org/uri4 http://example.org/predicate4 http://example.org/uri5 http://example.org/uri1 http://example.org/predicate1 "literal1" http://example.org/uri1 http://example.org/predicate1 "literalA" http://example.org/uri1 http://example.org/predicate1 "literalB" http://example.org/uri1 http://example.org/predicate1 "literalC" http://example.org/uri1 http://example.org/predicate2 http://example.org/uri3 http://example.org/uri1 http://example.org/predicate2 http://example.org/uriA3 http://example.org/uri2 http://example.org/predicate1 "literal1" 9 results shown. >> http://example.org/uri3 ? ? http://example.org/uri3 http://example.org/predicate3 http://example.org/uri4 http://example.org/uri3 http://example.org/predicate3 http://example.org/uri5 2 results shown. >> exit
Exporting the header
The header component of an HDT contains metadata describing the data contained in the HDT, as well as the creation metadata about the HDT itself. The contents of the header can be exported to an N-Triples file:
$ ./hdtInfo data.hdt > header.nt
Replacing the Header
It can be useful to update the header information of an HDT. This can
be done by generating a new HDT file (
new.hdt) out of an existing
HDT file (
old.hdt) and an N-Triples file (
contains the new header information:
$ ./replaceHeader old.hdt new.hdt new-header.nt
Contributions are welcome! Please base your contributions and pull
requests (PRs) on the
develop branch, and not on the
hdt-cpp is free software licensed as GNU Lesser General Public
License (LGPL). See