Lesson 1 The subgraph operator

Test Data Schema

All labels start with a lowercase letter in our dataset, so please use 'person' instead of 'Person' in your tasks.

Task 1 - Filter by label

• Create a subgraph that contains ‘person’ vertices and ‘knows’ edges only.

Solution

Use the ByLabel class to filter for vertices/edges of a specific label.

graph = graph.subgraph(new ByLabel<>("person"), new ByLabel<>("knows"));

Task 2 - Logical operators

• Get universities and persons that used the browser Firefox.
• Include all relationships between these vertices.

Some help

• Use the function .vertexInducedSubgraph() to only filter for vertices and get all edges between them.
• Use the ByLabel or LabelIsIn classes to filter for vertices/edges of a specific label.
• Use the ByProperty class to filter for elements with a specific property and optional a value.
• Use the And and Or classes to build boolean relations.

Solution

graph = graph.vertexInducedSubgraph(
    new Or<>(
      new ByLabel<>("university"),
      new And<>(new ByLabel<>("person"), new ByProperty<>("browserUsed", PropertyValue.create("Firefox")))));

Task 3 - User-defined filter

• Some edge types have a creationDate property. Get all edges that contain this property and are crated in the period [2012-01-01 00:00 , 2012-01-05 00:00) by using a user-defined edge filter function.
• Only the source and target vertices of these edges should be included.
• Optional: Use parameters (by adding a constructor) to define the lower and upper bound for the condition.

Some help

• Use the function .edgeInducedSubgraph() to only filter for edges and get all connected vertices.
• You can check the availability of a property by edge.hasProperty("myProperty").
• You get the value of a propety by calling edge.getPropertyValue("myProperty").get{dataType}()

Solution

This is the solution of the task with the optional subtask included.

graph = graph.edgeInducedSubgraph(
    new CreatedInPeriod<>(LocalDateTime.of(2012, 1, 1, 0, 0), LocalDateTime.of(2012, 1, 5, 0, 0)));

private static class CreatedInPeriod<E extends Edge> implements FilterFunction<E> {

  private LocalDateTime lowerBound, upperBound;

  public CreatedInPeriod(LocalDateTime start, LocalDateTime end) {
    this.lowerBound = start;
    this.upperBound = end;
  }

  @Override
  public boolean filter(E edge) throws Exception {
    if (edge.hasProperty("creationDate")) {
      LocalDateTime creationDate = edge.getPropertyValue("creationDate").getDateTime();
      return (creationDate.isEqual(lowerBound) || creationDate.isAfter(lowerBound)) &&
        creationDate.isBefore(upperBound);
    }
    return false;
  }
}