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Home Tools SPARQL

Overview

The TALOS SPARQL Query Endpoint lets you interact with the project's linked open data repositories through a browser. It is aimed at researchers, scholars and students working on ancient studies, linguistic modelling and semantic web research — including those with no prior SPARQL experience, since every dataset ships with worked example queries you can load and edit.

What it does

  • Dataset and example-query selection
  • A SPARQL editor with prefix insertion and query validation
  • Results table with filtering, sorting and pagination
  • Export to CSV, JSON and RDF
  • Built-in help, keyboard shortcuts and a light/dark theme

Getting started

Nothing to install. The tool runs at tools.talos-lab.eu/sparql in any recent version of Chrome, Firefox or Edge, at a minimum display resolution of 1280×720.

  1. Open the URL above.
  2. Pick a dataset from the Select Dataset dropdown and click Load Dataset.
  3. Optionally choose a predefined query from Example Queries to load it into the editor.
  4. Click Execute Query, or press Ctrl + Enter.
  5. Filter, page through, and export the results.
The endpoint home screen, showing the dataset selector and empty query editor
Figure 1. The home interface on first load.

The interface

The screen divides into four areas.

  1. Header: application title and logo, the Help button, and the light/dark theme toggle.
  2. Dataset & example section: dataset selector, example-query menu, and the dataset's name, description and graph URI once loaded.
  3. Query editor: where you compose SPARQL, with prefix insertion and validation.
  4. Results display and export panel: the results table plus the CSV, JSON and RDF export buttons.
Wireframe of the application layout with the four numbered regions
Figure 2. Layout overview.

Running queries

SPARQL is the standard query language for data held as RDF triples. If you have written SQL before, the shape will feel familiar; the difference is that you are matching graph patterns rather than joining tables.

PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>

SELECT ?subject ?predicate ?object
WHERE {
  ?subject ?predicate ?object .
}
LIMIT 100

Press Ctrl + Enter to execute, or Ctrl + / to comment and uncomment lines. Prefixes can be inserted from the Prefixes button rather than typed out.

A query and its results table, showing philosophical works and philosopher names
Figure 3. A query and its results.

Query types

  • SELECT: returns tabular data
  • CONSTRUCT: generates RDF triples; preferred for RDF export
  • ASK: returns true or false
  • DESCRIBE: returns a description of a resource

Writing queries that finish

  • Constrain results with LIMIT while you are still exploring.
  • Filter by language where labels are multilingual, e.g. FILTER(LANG(?label) = 'en').
  • Avoid OPTIONAL clauses you do not need, and wide chains of them in particular.
  • Heavy regex() filters are expensive; prefer exact matches where you can.

Datasets

Each dataset lives in its own named graph, and each ships with predefined example queries. Every one has its own page describing what it models. See the dataset index. Currently available:

The dataset information panel showing name, description and graph URI
Figure 4. Dataset information after loading.

Graph URIs must match exactly: the app validates the FROM <...> clause in your query against the loaded dataset's graph IRI. A mismatch produces a validation error rather than an empty result, which is usually the faster thing to debug.

Results & export

Results render in a table with pagination, sorting, and a Filter results box that narrows the current result set as you type. URIs in the table are clickable and open in a new tab.

Results table filtered to matching rows, with matches highlighted
Figure 5. Filtering within a result set. The row count shows both the filtered and total figures.

Exporting

Run a query, then click CSV, JSON or RDF; the file downloads immediately. Exports preserve URI links and variable headers, and a filtered view exports as filtered rather than in full.

  • CSV: for spreadsheet analysis
  • JSON: for further structured processing
  • RDF: for semantic data exchange; use a CONSTRUCT query for best results

Troubleshooting

Query fails

The query will not execute

Usually a syntax error, or a FROM clause that does not match the loaded dataset. Check the syntax, then confirm the graph URI is identical to the one shown in the dataset panel.

Syntax / graph URI
Empty result

No results returned

The conditions are probably too restrictive. Remove filters one at a time, or relax the language filter, until rows appear.

Over-filtering
Slow

The query takes a long time

Large graph. Add a LIMIT, filter by language, and drop any unnecessary OPTIONAL clauses.

Dataset size

The Help button in the app itself carries the same guidance, plus shortcuts and syntax examples. For anything else, contact TALOS AI4SSH support or use the contact form on the project site.

Citation & licence

Developed by Maria Schoinaki, within the Horizon Europe project grant agreement 101087269.

Licence

Released under the PolyForm Noncommercial 1.0.0. You may use, modify and share it for any purpose that is not primarily intended for commercial advantage or monetary compensation: research, teaching and personal use all qualify. Copies and modified versions must carry the licence and the notices that came with them. The software is provided as is, without warranty.

PolyForm Noncommercial is a source-available licence rather than an open source one: the noncommercial restriction is not permitted under the Open Source Definition.

Citation

Schoinaki, M. (2025). TALOS SPARQL Query Endpoint (version 1.0).
TALOS AI4SSH Laboratory, University of Crete.
https://tools.talos-lab.eu/sparql/.