LDAF
Linked Data Application Framework

Application developers, in our experience, tend to hesitate when dealing with linked data technologies. To reduce their initial hurdle and enable rapid prototyping, we propose a framework for building linked data applications. Our approach especially considers the participation of web developers and non-technical users without much prior knowledge about linked data concepts. Web developers are supported with bidirectional RDF to JSON conversions and suitable CRUD endpoints. Non-technical users can browse websites generated from JSON data by means of a template language.

Authors

• Markus Schröder
• Christian Jilek
• Andreas Dengel

You can try out a publicly available online demo.
The following links and CURL commands can be used to test the demo. Remember that the JWT has to be entered with --cookie token= for endpoints that require authentification. A REST client (like Insomnia) makes it easier to send requests. Read the tutorial to see how the endpoints below were implemented.

Use Case	HTML For non-technical users	JSON For web developers	RDF For Semantic Web practitioners
Registration	/ Use the registration secret: another-secret.	curl --request POST \ --url http://ldaf.dfki.markus-projects.net/auth/registration \ --header 'content-type: application/json' \ --data '{ "firstName":"Test", "lastName":"Test", "userName":"test", "password":"test", "secret":"another-secret" }'
Login	/ For testing you may use username: admin password: a-secret After login you are redirected to /user/admin, but this is not implemented in the example.	curl --request POST \ --url http://ldaf.dfki.markus-projects.net/auth/login \ --header 'content-type: application/json' \ --data '{ "userName": "admin", "password": "a-secret" }'
Browse Ontology	/ontology	curl --request GET \ --url http://ldaf.dfki.markus-projects.net/ontology \ --header 'accept: application/json'	curl --request GET \ --url http://ldaf.dfki.markus-projects.net/ontology \ --header 'accept: text/turtle'
Search	/search?q=test	curl --request GET \ --url http://ldaf.dfki.markus-projects.net/search?q=test \ --header 'accept: application/json'	curl --request GET \ --url http://ldaf.dfki.markus-projects.net/search?q=test \ --header 'accept: text/turtle'
SPARQL	/sparql The prefix has to be set to PREFIX ex: <http://ldaf.dfki.markus-projects.net/ontology/>		curl 'http://ldaf.dfki.markus-projects.net/sparql' \ -H 'Accept: application/sparql-results+json,*/*;q=0.9' \ -H 'Content-Type: application/x-www-form-urlencoded' \ --data-raw 'query=PREFIX%20rdf%3A%20%3Chttp%3A%2F%2Fwww.w3.org%2F1999%2F02%2F22-rdf-syntax-ns%23%3E%0APREFIX%20rdfs%3A%20%3Chttp%3A%2F%2Fwww.w3.org%2F2000%2F01%2Frdf-schema%23%3E%0APREFIX%20ex%3A%20%3Chttp%3A%2F%2F173%2E212%2E240%2E179%3A6570%2Fontology%2F%3E%0A%0Aselect%20*%0A%7B%0A%20%20%3Fguideline%20a%20ex%3AGuideline%20.%0A%20%20%3Fguideline%20rdfs%3Alabel%20%3Flabel%20.%0A%7D%0Aorder%20by%20%3Flabel%0Alimit%2010%0A'
Upload Image	/upload	curl 'http://ldaf.dfki.markus-projects.net/upload' \ -H 'Accept: application/json' \ --compressed \ -H 'X-Requested-With: XMLHttpRequest' \ -H 'Content-Type: multipart/form-data; boundary=---------------------------136835826728715030583565956947' \ --data-binary $'-----------------------------136835826728715030583565956947\r\nContent-Disposition: form-data; name="uploaded_file"; filename="image.png"\r\nContent-Type: image/png\r\n\r\n-----------------------------136835826728715030583565956947--\r\n' (still needs binary image data)
List Guideline Resources	/guideline	curl --request GET \ --url http://ldaf.dfki.markus-projects.net/guideline \ --header 'accept: application/json'	curl --request GET \ --url http://ldaf.dfki.markus-projects.net/guideline \ --header 'accept: text/turtle'
Retrieve a Single Guideline Resource	/guideline/1	curl --request GET \ --url http://ldaf.dfki.markus-projects.net/guideline/1 \ --header 'accept: application/json'	curl --request GET \ --url http://ldaf.dfki.markus-projects.net/guideline/1 \ --header 'accept: text/turtle'
Create a Guideline Resource	/guideline Use provided forms	curl --request POST \ --url http://ldaf.dfki.markus-projects.net/guideline \ --header 'content-type: application/json' \ --data '{ "label": "Another GL", "hasTitle": "Another GL", "hasNote": "This is another one", "validFrom": "2021-03-09" }'
Change a Guideline Resource	/guideline/1?edit Use provided forms	curl --request PATCH \ --url http://ldaf.dfki.markus-projects.net/guideline/1 \ --header 'content-type: application/json' \ --data '{ "hasNote": "Change the note" }'
Delete a Guideline Resource	/guideline/1 Use Delete button, but don't be surprised if this resource has already been deleted.	curl --request DELETE \ --url http://ldaf.dfki.markus-projects.net/guideline/1
A custom resource	/own	curl --request GET \ --url http://ldaf.dfki.markus-projects.net/own \ --header 'accept: application/json'	curl --request GET \ --url http://ldaf.dfki.markus-projects.net/own \ --header 'accept: text/turtle'
Another custom resource	/another	curl --request GET \ --url http://ldaf.dfki.markus-projects.net/another \ --header 'accept: application/json'	curl --request GET \ --url http://ldaf.dfki.markus-projects.net/another \ --header 'accept: text/turtle'

The source code can be found on GitHub. Our example application is the one that is hosted for demonstration.