Psepheda (ΨΗΦΙΔΑ) — University of Macedonia Institutional Repository

Dataset Language
Modern Greek (primary), with a minority of English-language academic content and occasional multilingual passages (Slavic/Balkan-studies material includes Cyrillic).

Dataset Info
This dataset is a cleaned, full-text snapshot of ΨΗΦΙΔΑ (Psepheda), the institutional repository and digital library of the University of Macedonia (Πανεπιστήμιο Μακεδονίας, Thessaloniki, Greece), served from dspace.lib.uom.gr. Psepheda is a DSpace repository in which students and staff self-deposit their academic work — overwhelmingly Master's theses and PhD dissertations, plus bachelor's projects, musical scores, and a number of historical archival documents (e.g. Hellenic Parliament records and old academic publications).

The dataset contains 14,303 records. Each row is one repository item: its catalogued bibliographic metadata plus the full text of the deposited PDF, extracted to Markdown. Coverage by issue date spans roughly 1900–2026, heavily concentrated in 2005–2025 (the period of mandatory electronic self-deposit). The bulk of the corpus comes from the University's postgraduate programmes in economics, business administration, applied informatics, accounting & finance, music science, education, and international/European studies (120 distinct repository collections in total).

Source & Provenance

• Every record links back to its canonical DSpace landing page (handle_url, e.g. http://dspace.lib.uom.gr/handle/2159/168) and the source PDF (pdf_url).
• The content field was produced by an LLM/vision-based PDF→Markdown extraction of those PDFs. This extraction is faithful for clean digital-born theses but degrades on hard-to-read pages (old scans, music scores, handwriting); see Cleaning & Known Quality Notes.

Metadata Info — Schema
The parquet has one row per repository item and 20 columns:

Column	Type	Description
title	string	Title of the document as catalogued by the repository.
content	string	Full text of the deposited PDF, extracted to Markdown (cleaned — see below). This is the main training text and is multi-KB to multi-MB per row.
abstract	string	Author/editorial abstract (Greek and/or English). May be empty.
description	string	Short descriptive note (often a thesis/programme statement).
description_full	string	Longer descriptive note, where present.
information	string	Cataloguer note, frequently of the form Διπλωματική εργασία--Πανεπιστήμιο Μακεδονίας, ….
subjects	string	Subject/keyword terms.
creator	string	Author/creator of the work.
contributors	string	Contributors (supervisor, examination committee, hosting postgraduate programme), ;-separated.
supervisor	string	Thesis/dissertation supervisor.
issue_date	string	Issue/publication date, usually YYYY (sometimes YYYY-MM).
type	string	Resource type, e.g. Electronic Thesis or Dissertation ; Text, Musical Score, Bachelor's Degree Paper.
publisher	string	Publisher (predominantly Πανεπιστήμιο Μακεδονίας).
department	string	Depositing department / faculty.
collection_name	string	Psepheda collection (typically a specific postgraduate programme).
title_alt	string	Alternative title, where present.
rights	string	Per-item rights/licence statement — authoritative for licensing. See the License section.
relations	string	Related-item references (mostly empty).
handle_url	string	Canonical DSpace handle landing page for the item.
pdf_url	string	Direct URL to the source PDF on dspace.lib.uom.gr.

Cleaning & Known Quality Notes
This release is derived from a raw extraction of 14,413 items through a documented, auditable QA pipeline. The raw → released chain is:

raw (14,413) → drop 98 hallucinated extractions → (14,315) → drop 12 English-only documents → released (14,303).

1. Removed 98 hallucinated extractions (−0.68%). On pages the extractor could not read (old scans, music scores, handwriting) it emitted multilingual gibberish — floods of CJK / Arabic / Hebrew / Indic / Georgian / Cherokee glyphs, often injected mid-word. Rows were dropped only when this foreign-script noise was severe (≥30 exotic letters or ≥20 script-mixing junctions, measured on the raw text). Cyrillic was deliberately excluded from this rule because it is legitimate in the Slavic/Balkan-studies collections, which are preserved.
2. Removed 12 genuinely English documents (−0.08%). Because this is a Greek corpus, documents that are English as a whole were dropped — but only when title, body, and (where present) abstract were all predominantly non-Greek. This conservative three-signal rule protects the many Greek theses whose bodies are Latin-heavy for legitimate reasons (code listings, mathematics, English citations, music/jazz catalogues).
3. Text cleaning applied to surviving content (formatting only). HTML entities were unescaped (including a double-escaped layer present in some captured web pages), non-breaking spaces normalized to regular spaces, broken local image placeholders ![alt](page_N.png) removed, runs of 3+ blank lines collapsed, and leading/trailing whitespace stripped. Source-faithful elements were preserved: table-of-contents dot leaders, inline <table> markup, and all Cyrillic text.

Quirks that were intentionally preserved (faithful to source): TOC dot-leaders, inline HTML tables, all four description-like fields (description, description_full, information, abstract), a small number of embargoed/metadata-only items whose content still extracted text, and the original per-item rights strings verbatim.

Dataset Statistics
Counts cover the text fields content + title + abstract (other columns are bibliographic metadata and are excluded), following the glossAPI convention.

• Records (rows): 14.303
• Repository collections: 120
• Issue-date coverage: ~1900 – 2026 (concentrated 2005–2025)
• Size on disk: 1,87 GB (parquet)
• Words: 376.107.060 (whitespace-separated, on content + title + abstract)
• Tokens: 769.348.015 (nlpaueb/bert-base-greek-uncased-v1 WordPiece tokenizer, no special tokens, no truncation)
• Characters: 2.892.686.626

Per-field breakdown (rows = 14.303):

Field	Non-empty	Characters	Words	Tokens
content	14.303	2.870.226.703	372.996.488	765.312.500
abstract	11.790	21.083.834	2.931.401	3.799.384
title	14.302	1.376.089	179.171	236.131

License
Important: this dataset carries mixed, per-item licensing. It aggregates self-deposited academic works whose authors each chose their own licence at deposit time. The repository tag for this dataset (cc-by-nc-nd-4.0) is a conservative umbrella reflecting the source repository's blanket terms; it is not a uniform grant. The authoritative licence for any individual record is its own rights field.

According to the University of Macedonia Library (openaccess.lib.uom.gr): "Use of all the digital content of the ΨΗΦΙΔΑ collections is personal and for educational, research and private purposes only, not for commercial purposes, unless a licence states otherwise." Bibliographic metadata is provided under CC BY-NC 3.0 Greece. Users are instructed to consult the Rights field of each record.

Distribution of the rights field across the 14,303 records:

Rights family	Records	Share
None / unspecified (default: all rights reserved)	6,406	44.8%
CC BY-NC-ND 4.0	2,839	19.8%
CC0 1.0	1,564	10.9%
CC BY-ND 4.0	745	5.2%
Embargoed (full text not released)	674	4.7%
CC BY 4.0	571	4.0%
CC BY-NC 4.0	548	3.8%
Hellenic Parliament (all rights reserved)	337	2.4%
CC BY-NC-SA 4.0	276	1.9%
CC BY-SA 4.0	143	1.0%
Law 2121/1993 digitization / bespoke / errors	~200	1.4%

Practical guidance for downstream users:

• Filter by the rights column for your use case. Roughly 22% of records carry a CC licence that clearly permits derivatives (CC0, BY, BY-SA, BY-NC, BY-NC-SA); about 25% are explicitly NoDerivatives (ND); about 53% have no open licence stated.
• Do not assume commercial rights. The repository's default is non-commercial, educational/research use.
• Attribute the original authors and the University of Macedonia / ΨΗΦΙΔΑ repository, and link back via handle_url.

Source: ΨΗΦΙΔΑ (Psepheda) — Library & Information Centre, University of Macedonia (dspace.lib.uom.gr). Copyright in each work remains with its original author(s); see each record's rights field.

Usage
This dataset is useful for:

• Greek-language NLP and language-model pretraining/adaptation over an academic / scientific register (economics, business, informatics, accounting, music, education, social sciences).
• Domain-adapted embeddings, terminology extraction, and retrieval/Q&A over Greek postgraduate research.
• Long-document modelling (many items are full theses of tens to hundreds of thousands of characters).

Contact
For feedback contact: glossapi.team@eellak.gr