pd_check/pd_check.md

# Public Domain Check - Confirming the author has died at least 70 years ago

## Summary

The goal of the check is to avoid uploading non-public domain data.  
The digitized documents obtained from the [Danish Royal Library](https://www.kb.dk/en) have a range of publishing dates from 1750 to 1930. 

According to [Danish law](https://www.retsinformation.dk/eli/lta/2023/1093) 70 years must pass after the death of the author(s) in order for these documents to become part of the [public domain](https://creativecommons.org/public-domain/).

Based on this, the data can be separated to 3 distinct groups:  
- **Published before 1833**: Even if the longest living human in modern history wrote that as soon as they were born, they still died more than 70 years ago
- **Copyright info supplied**: The Danish Royal Library provides meta data on several of these documents, in which they claim the writing is indeed part of the public domain
- **The rest**: Documents where public domain status has to be investigated

To confirm whether a document is part of the public domain or not, the author(s) indicated in the meta data were matched against a database of potential Danish authors. Both their full names and potential abbreviations were used. A document was marked as being in the public domain if:  
- All authors were matched to at least one name in the reference database
- All of these matches had complete biographic information in the reference database
- The author(s) died at least 70 years ago
- The author(s) have been born at least 18 years before the publication date

It must be noted, that the digitization took place over the course of several years, the provided meta data mostly follows a standard layout, but some documents might differ in that regard. This can be a potential source of errors.

**In case some non-public domain document is found in the dataset, please contact us**


The matched authors and written media is available for reference in .json format as [public_domain_appendix_4.json](./public_domain_appendix_4.json)  
The list of only the filenames of the selected works (used in the extraction process, and is probably less important to outside parties) is available as [public_domain_files.txt](./public_domain_files.txt) + the manual appendices.

### Manual Appendix 1
The automated matching does not make a distinction if two possible authors have the same name. This is a source of errors, therefore to ensure dataset integrity regarding copyright, documents published in the 20th century were manually re-inspected.
Documents from ambigous authors were removed from the data.
### Manual Appendix 2
Partial matches were manually investigated, where out of all authors of a document, there was at least one with a match. Most of these documents were identified as belonging to the public domain. These typically include: 
- Pseudonyms, identified as a separate author
- Translations
- Some authors missing from the Wiki scraped data, but identified manually through [LEX](https://lex.dk/) or [Dansk Forfatterleksikon](https://danskforfatterleksikon.dk/)

### Manual Appendix 3
Dual Author files with no automatic matches were investigated for similar patterns as the ones found in Manual Appendix 2

### Manual Appendix 4
Single author files with no automatic matches were investigated based on the authors investigated in Manual Appendix 2 and 3.

The resulting [metadata](./public_domain_appendix_4.json) after the manual inspections is also provided.
## Sources

Potential authors were gathered using [Web Scraping](../scrape/scraping.md)

## Logic

The flowchart is for a broad understanding and is not a fully accurate representation.

![Logic flowchart](./imgs/pd_check_flowchart.jpg)

The whole python script is provided for reference as [select_pd.py](./select_pd.py)  

Made with:  

- python 3.12.10  

Required libraries for running:  

- [PyMuPDF](https://pypi.org/project/PyMuPDF/) 1.26.0
- [datasets](https://pypi.org/project/datasets/)  3.5.0