Subgraph-query.

CTCS_report_template/CTCS_template.tex

@@ -176,7 +176,17 @@ The framework was implemented in \emph{Java}. We used \emph{Maven} as a project
 \subsection{Fetching Knowledge Graphs}
 Because \emph{knowledge graphs} can be very large and contain many nodes, we concentrated on fetching smaller subgraphs and only working on those. With this method, the relevant subgraph gets extracted from a \emph{knowledge graph} and can be worked upon in isolation.
 We take our initial \emph{knowledge graphs} from the \emph{CommonCrawl} datasets and import them as a static file.
-\todo{Explain query magic that fetches the graph here}\\
+\todo{Explain query magic that fetches the graph here}
+
+\Valerian{Figure~\ref{fig:query_construct_subgraph} shows the query we used to create this subgraph. At line 7 we used \emph{property paths}\footnote{\url{https://www.w3.org/TR/2013/REC-sparql11-query-20130321/\#propertypaths}} to query all nodes connected to those of an initial subset (lines 10 to 13). This subset can optionally be limited to a certain size, but is always limited to nodes of a certain type.}
+
+\begin{figure}
+    \centering
+    \lstinputlisting{code_snippets/subgraph.sparql}
+    \caption{The \emph{SPARQL}-query creating the subgraph. The \emph{\%s} get substituted before executing the query.}
+    \label{fig:query_construct_subgraph}
+\end{figure}
+
 
 \Valerian{Missing: Subsection about generating subgraph (with limit), starting from a certain type of node.} \Kristina{Wouldn't this be part of Generating constraints? I feel like that doesn't really fit into technology stack}
 \Danielle{I agree with Kristina here.}

CTCS_report_template/code_snippets/subgraph.sparql

+CONSTRUCT {
+  ?s ?p ?o
+}
+%s                                     # %s replaced by optional graph-name
+WHERE {
+  GRAPH ?g {
+    ?subject (<>|!<>)* ?s . 
+    ?s ?p ?o .
+    {
+      SELECT DISTINCT ?subject
+      WHERE {
+        GRAPH ?g { ?subject a %s }    # %s replaced by type of starting-nodes
+      } %s                            # %s replaced by optional limit
+    }
+  }
+}