Java - Google App Engine - modeling county structures in a Google data warehouse

Question

The Google Apps Engine offers the Google data warehouse as the only NoSQL database (I think it is based on BigTable).

In my application, I have a structure similar to a social structure, and I want to model it the way I would do in the graph database. My application should save heterogeneous objects (users, files, ...) and the relationships between them (e.g. user1 OWNS file2, user2 FOLLOWS user3, etc.).

I am looking for a good way to simulate this typical situation, and I thought of two families of solutions:

• List Based Solutions. Any object contains a list of other related objects, and the presence of an object in the list itself is a relation (as Google said in the JDO part https://developers.google.com/appengine/docs/java/datastore/jdo/relationships ).

• Graphical solution: both nodes and relationships are objects. Objects exist independently of a relationship, while each relationship contains a link to two (or more) related objects.

What are the strengths and weaknesses of these two approaches?

About approach 1: This is a simpler approach that you can think of, and it is also presented in the official documentation, but:

• Each directional relation increases the indicator of the object: are there any restrictions on the number of possible relations given, for example, by the measurement limit of the object?
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Answer 1

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Answer 2

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Answer 3

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class User(db.User):
  followers = db.StringListProperty()

.

user = User.get(key)
user.followers.append(str(followerKey))

User.all().filter('followers', followerKey) # -> followed

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class User(db.User):
  followers = db.StringListProperty()
  follows = db.StringListProperty()

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