LOD Cloud Draw

This is a tool for creating linked open data cloud diagrams, such as those found at http://lod-cloud.net/.

Installation

This project is written in Rust and can be compiled with Cargo as follows

cargo build --release

This will create a binary under target/release/lod-cloud-draw that can be used to create cloud diagrams

Requirements

To use this library you must have gfortran installed in your pc

• for windows use fortran compiler provided by mingw or TDM-GCC
• for linux you can use the package manager to install gfortran
• for Mac os you can install it from here or here

Details

Tool used to create LOD cloud diagrams as SVG. The cloud is created as a minimization of the following function:

f(V,E) = s sum_{e} spring(e) + r sum{v1} sum{v2} repulse(v1, v2, d) + w * sum_{v} well(v, c)

Where:

• spring(e): Measures the length of a link in the cloud
• repulse(v1, v2, d): Indicates if v1 and v2 are within a distance of d
• well(v, c): Indicates if v is contained within a circle (well) of radius c

And s,r,w are tuning constants

Usage

lod-cloud-draw [OPTIONS] <data.json> <output.svg>

FLAGS

-h, --help       Prints help information
-V, --version    Prints version information

OPTIONS

    --algorithm <cg|lbfgsb>          The algorithm used to find the cloud diagram (cg=Conjugate
                                     Gradient or lbfgsb = Limited BFGS)
-w, --well <FORCE>                   The value of the well boundary force
    --canvas-rigidity <FACTOR>       The rigidity of the well
-c, --canvas <PIXELS>                The radius of the circle that the bubbles should be contained in
    --ident <none|neighbour|tags>    The algorithm used to identify domain (bubble colours) of unidentified datasets
-i, --max-iters <ITERATIONS>         The maximum number of iterations to perform (default=10000)
-n, --n-blocks <BLOCKS>              Apply an n x n blocking method to speed up the algorithm 
                                     (default=1, no blocking)
-r, --repulse <FORCE>                The value of the repulsion force
-d, --distance <PIXELS>              The minimal distance between bubbles
    --repulse-rigidity <FACTOR>      The rigidity of repulsion between bubbles
-e, --settings <settings.json>       The JSON file containing the settings for the system
-s, --spring <FORCE>                 The value of the spring force

ARGS

<data.json>     The data of the LOD cloud
<output.svg>    The path of the SVG file to write to

Settings

In order to create a cloud diagram a settings file is required, this is a JSON file as follows

• legend: The legend (categories) to show; an array of legend entries (see below)
• fixed_points: If any datasets should occur at a fixed position; dictionary of strings to an array of two floating point numbers
• selection: Selection method: Either "all", "dataset" or "domain"
• selected: The value of the dataset/domain to be selected
• hops: The number of hops from a dataset in dataset mode
• datasets: Any datasets that must be included in the data
• rights_text: The description and copyright text
• logo_link: The logo (link) (to be included in the bottom right of the image)
• logo_width: The logo width

Legend entries consist of the following

• title: The display title to be shown to the user
• domain: The value of the domain property in data that corresponds to
• colour: The (HTML) colour of this legend
• keywords: The keywords that identify this domain

Examples of this may be found under the clouds folder

Data

Data may be obtained from the following URL

https://lod-cloud.net/lod-data.json

Rebuilding from the live version can be done with the following command

python3 scripts/get-data.py