As discussed earlier, comments can be used by users to ask more questions or clarify something to other users. Since chronology is important, we will create a chain for the comments. The assumption here is that for a new question or clarification, a new comment chain will be started with the first comment in the chain being in response to the review being commented on.

Before we add comments, we should set up a constraint on comments to ensure that we don't create comments with the same ID, as shown in the following query:

neo4j-sh (?)$ CREATE CONSTRAINT ON (comment:Comment) ASSERT comment._id IS UNIQUE;

The output of the preceding query is as follows:

+-------------------+
| No data returned. |
+-------------------+
Constraints added: 1

To add a comment to the review, we can use the following query:

CREATE (comment:Comment{_id:"df23c188-2349-11e5-8966-6c40089a9424", text:"What was wrong with the service?", created_on: 1391550607.342643}))
WITH comment
MATCH (review:Review...