Extract signposts from jsonld (#1)

* use rdflib to extract signposts from jsonld

* use rdflib to extract signposts from jsonld

* linting

* unit tests for jsonld middleware

* update readme

* update flake pipeline

---------

Co-authored-by: Daniel Bauer <daniel.bauer@senckenberg.de>

django_signposting/sparql.py

@@ -0,0 +1,136 @@
+from rdflib import Graph
+from rdflib.query import Result
+
+
+def root_element_query(g: Graph) -> Result:
+    return g.query("""
+PREFIX schema: <http://schema.org/>
+
+SELECT DISTINCT ?rootElement
+WHERE {
+  # has a type
+  ?rootElement a ?type ;
+  # has a license or an author or a creator
+  (schema:license | schema:author | schema:creator ) ?value .
+
+  # No incoming edges for ?rootElement
+  FILTER NOT EXISTS { ?s ?p ?rootElement }
+}
+LIMIT 1
+""")
+
+
+def type_query(g: Graph, rootElement: str) -> Graph:
+    return g.query(
+        """
+PREFIX schema: <?context>
+
+SELECT DISTINCT ?type
+WHERE {
+  ?rootElement a ?type .
+}
+""",
+        initBindings={"rootElement": rootElement},
+    )
+
+
+def author_query(g: Graph, rootElement: str):
+    return g.query(
+        """
+PREFIX schema: <http://schema.org/>
+
+SELECT ?author_id ?identifier ?url
+WHERE {
+    ?rootElement schema:author ?author .
+
+    BIND(?author AS ?author_id)  # Get the @id of the author
+    OPTIONAL { ?author schema:identifier ?identifier }
+    OPTIONAL { ?author schema:url ?url }
+}
+LIMIT 1
+
+""",
+        initBindings={"rootElement": rootElement},
+    )
+
+
+def license_query(g: Graph, rootElement: str):
+    return g.query(
+        """
+PREFIX schema: <http://schema.org/>
+
+SELECT ?element_id ?identifier ?url
+WHERE {
+    ?rootElement schema:license ?element .
+
+    BIND(?element AS ?element_id)  # Get the @id of the element
+    OPTIONAL { ?element schema:identifier ?identifier }
+    OPTIONAL { ?element schema:url ?url }
+}
+LIMIT 1
+""",
+        initBindings={"rootElement": rootElement},
+    )
+
+
+def cite_query(g: Graph, rootElement: str):
+    return g.query(
+        """
+PREFIX schema: <http://schema.org/>
+
+SELECT ?element_id ?identifier ?url
+WHERE {
+    ?rootElement schema:url ?element .
+
+    BIND(?element AS ?element_id)  # Get the @id of the element
+    OPTIONAL { ?element schema:identifier ?identifier }
+    OPTIONAL { ?element schema:url ?url }
+}
+LIMIT 1
+
+""",
+        initBindings={"rootElement": rootElement},
+    )
+
+
+def sameas_query(g: Graph, rootElement: str):
+    return g.query(
+        """
+PREFIX schema: <http://schema.org/>
+
+SELECT ?element_id ?contentUrl ?identifier ?url ?encoding
+WHERE {
+    ?rootElement schema:sameAs ?element .
+
+    BIND(?element AS ?element_id)  # Get the @id of the element
+    OPTIONAL { ?element schema:contentUrl ?contentUrl }
+    OPTIONAL { ?element schema:identifier ?identifier }
+    OPTIONAL { ?element schema:url ?url }
+    OPTIONAL { ?element schema:encodingFormat ?encoding }
+}
+""",
+        initBindings={"rootElement": rootElement},
+    )
+
+
+def item_query(g: Graph, rootElement: str):
+    return g.query(
+        """
+PREFIX schema: <http://schema.org/>
+
+SELECT ?element_id ?identifier ?url ?contentUrl ?encoding
+WHERE {
+    ?rootElement schema:hasPart ?element .
+    #VALUES ?element_type { schema:MediaObject schema:Dataset }
+    #?element a ?element_type .
+
+    BIND(?element AS ?element_id)  # Get the @id of the element
+    OPTIONAL { ?element schema:contentUrl ?contentUrl }
+    OPTIONAL { ?element schema:identifier ?identifier }
+    OPTIONAL { ?element schema:url ?url }
+    OPTIONAL { ?element schema:encodingFormat ?encoding }
+}
+
+""",
+        initBindings={"rootElement": rootElement},
+    )