Infographic Describer

Infographic Describer

Generate RDF-Turtle descriptions for files in a WebDAV-hosted directory using a SHACL shape as the property contract.

Workflow

Step 1: Discover Files

List the target WebDAV directory to enumerate files:

curl -sL "https://www.openlinksw.com/data/{directory}/" | python3 -c "
import sys, re
html = sys.stdin.read()
files = re.findall(r'title=\"File - ([^\"]+)\"', html)
for f in files:
    print(f)
"

Classify by extension: .png → schema:ImageObject, .mp4 → schema:VideoObject, .html → schema:WebPage.

Step 2: Probe Describe Endpoint

Check which files have existing RDF data in the triplestore. Use the SPARQL DESCRIBE endpoint:

import urllib.parse, urllib.request

iri = f'https://www.openlinksw.com/DAV/www2.openlinksw.com/data/{directory}/{stem}.{ext}'
query = f'DESCRIBE <{iri}>'
url = 'http://www.openlinksw.com/sparql?query=' + urllib.parse.quote(query) + '&output=text%2Fn3'

req = urllib.request.Request(url, headers={'Accept': 'text/n3, */*'})
resp = urllib.request.urlopen(req, timeout=30)
data = resp.read().decode()
has_data = 'Empty' not in data and len(data.strip()) > 50

Step 3: Probe Thumbnails

Check for thumbnails using the content-explorer pattern:

https://www.openlinksw.com/data/content-explorer/thumbnails/{category}-{stem}.avif

Where {category} is the directory name (e.g., infographics). Probe with HTTP HEAD:

curl -sL -o /dev/null -w "%{http_code}" "$url"

Only files with 200 have thumbnails.

Step 4: Generate Descriptions

For each file, construct RDF triples using the SHACL shape properties:

Entity IRI pattern: {contentUrl}#this

Category IRIs (content-explorer-metadata.ttl):

• #Infographic — default for /data/infographics/
• #Guide — filenames containing "guide"
• #Demo — filenames containing "demo"
• #Survey — filenames containing "survey"

Encoding format mapping:

• .png → image/png
• .jpg/.jpeg → image/jpeg
• .mp4 → video/mp4
• .html → text/html

Step 5: Generate Turtle

Use this template structure:

@prefix schema: <http://schema.org/> .
@prefix rdf:    <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix wdrs:   <http://www.w3.org/2007/05/powder-s#> .
@prefix xsd:    <http://www.w3.org/2001/XMLSchema#> .

<{contentUrl}#this>
    a {schemaType} ;
    schema:name "{name}" ;
    schema:description "{description}" ;
    schema:encodingFormat "{mimeType}" ;
    schema:contentUrl <{contentUrl}> ;
    schema:category <{categoryIri}> ;
    wdrs:describedby <{describeUrl}> .

Add schema:thumbnailUrl only if the probe returned 200.

Step 6: Validate

Validate the generated Turtle:

from rdflib import Graph
g = Graph()
g.parse('output.ttl', format='turtle')
print(f'{len(g)} triples, {len(set(g.subjects()))} entities')

Step 7: Save

Save to the user-designated output path. Default:

• Shapes: /Users/kidehen/Documents/RDF_DATA/shacl-shapes/
• Descriptions: same directory as the shapes

SHACL Shape Conventions

When generating or updating SHACL shapes to match describe output:

• Use sh:minCount 0 for properties that may not exist for all files (thumbnailUrl, dateCreated, dateModified)
• Use sh:minCount 1 for always-present properties (name, contentUrl, encodingFormat, type)
• Use sh:hasValue for fixed values (e.g., encodingFormat = "image/png")
• Use sh:targetClass to match the schema type

Notes

• The /describe endpoint requires a POST with h=1 to bypass the confirmation dialog
• Most files in a DAV directory will have sparse or no RDF data — filename-derived metadata is the norm
• Thumbnails are rare — only files processed by the content-explorer system have them
• The SPARQL DESCRIBE endpoint (without CBD mode) returns more data than CBD mode for these resources