SemOpenAlex is a dataset about scientific publications presented in the form of a knowledge graph.

The underlying SemOpenAlex dataset is based on OpenAlex. The original dataset snapshots of OpenAlex are updated about once per month. With the scripts provided in this repository, the SemOpenAlex dataset can be re-generated based on the snapshot.

In the sections below, we describe the detailed steps create and load the SemOpenAlex dataset.

To generate the SemOpenAlex dataset from the OpenAlex S3 bucket, we use the following python scripts for each entity. Each individual script downloads the latest snapshot and produces a RDF document in the TRIG format.

1. semopenalex-authors.py
2. semopenalex-concepts.py
3. semopenalex-institutions.py
4. semopenalex-publishers.py
5. semopenalex-sources.py
6. semopenalex-works.py
7. semopenalex-funders.py

Note that the semopenalex-dataset.py script is used to capture metadata about SemOpenAlex dataset (e.g. when it was loaded).

To be able to run the above Python scripts, we need:

• Python 3.7 (or later)
• Python's package management tool pip

Linux Server/OS:

• disk storage space of at least 4TB
• vCPU 16
• RAM of at least 256GB

GraphDB:

• 10.0.0 (or later)
• Docker installed (version >= 17.x , check with docker --version)
• docker-compose installed (version >= 1.14, check with docker-compose --version)

The required Python libraries are defined in the requirements.txt file. The following command can be used to install all dependencies.

$ pip install -r requirements.txt

In order to execute the main script, it requires the data_dump_input_root_dir location to be defined. You can modify and adjust the following directory inside all the Python scripts code as needed.

The default location is /opt/openalex-snapshot. Note that the folder must be mounted to a disk storage with at least 5TB.

data_dump_input_root_dir = '/opt/openalex-snapshot'

Depending on resources available on your Linux server, you can fine-tune multiprocessing for the following Python scripts:

1. semopenalex-authors.py
2. semopenalex-works.py

Currently, CPU_THREADS defaults to 16 and maxtasksperchild id defaults to 5.

In order to load the SemOpenAlex RDF dataset (i.e. billions of statements) to GraphDB, we use the ImportRDF tool, specifically preload with docker. To achieve an optimal performance for loading such large amounts of RDF data, we recommend using GraphDB SE/EE features (for example, multi-threading).

Note, that GraphDB can be started without a license pre-configured. As of GraphDB 10 the database will operate in Free Mode. To activate GraphDB SE/EE features, a valid license can be copied to the following place:

./graphdb-preload/graphdb-license/graphdb.license

You may also need to tune memory reservations, memory limits for the Docker and min and max values for Java heap memory for GraphDB according to the available resources, see docker-compose.yml

Before executing the following single main script (which runs all Python scripts as well as the data ingestion to GraphDB), there are few things you need to consider.

First, to perform data transformation step: from OpenAlex to SemOpenAlex RDF dataset, it typically takes at least 3-4 days in our system environment (vCPU: 16 and RAM 256 GB).

Second, to perform data ingestion to GraphDB, it also typically takes up 2-3 days. The overall time taken may depend and may be faster if you have bigger the computation power.

Third, we compress graphdb-home/ folder. This is for us to transfer the folder to another dedicated server for hosting the production database. You can skip or disable this step if you intend to run GraphDB in the same server.

Another note, in order to avoid the main script to be accidentally terminated, we recommend using linux screen or alike command to run it in the background.

$ chmod +x transformSemOpenAlex.sh
$ ./transformSemOpenAlex.sh