[Neo] Choosing between a property or a node

Mattias Persson mattias at neotechnology.com
Fri Feb 19 13:54:46 CET 2010


2010/2/19  <rick.bullotta at burningskysoftware.com>:
>   Mattias (and everyone) - can you see a way to model multiple
>   relationships of the same type between two nodes?  We have  few cases
>   where the relationship is essentially the same "type" but might have
>   different properties.  Max's "Class/Teacher" scenario is
>   somewhat similar.
Yes, I've used such models a couple of times and it's a completely
valid usecase in some scenarios (not any particular comes to mind
though).

You're suggesting something like: we have a "Math A" class node and
it'll have relationships to all teachers and students who have
attended that class? You would then "loose" the information about
which students have attended a specific class instance (f.ex. autumn
2009 or something) with a specific teacher (if you don't store that
information on every Teacher ----> Class relationship and Student
----> Class relationship). Did I understand you correct?
>
>
>
>   Rick
>
>
>
>   -------- Original Message --------
>   Subject: Re: [Neo] Choosing between a property or a node
>   From: Mattias Persson <mattias at neotechnology.com>
>   Date: Fri, February 19, 2010 4:27 am
>   To: Neo user discussions <user at lists.neo4j.org>
>   I've included some first thoughts on how you could model this. The
>   choice of properties/index vs. relationships is often quite obvious,
>   but is some cases you'll have to try and see which fits best. But
>   neo4j encourages you to create relationships if you're in doubt and
>   it's often better to use more relationships types than fewer, i.e.
>   it's good to be as specific as possible when modelling your graph.
>   2010/2/19 Max De Marzi Jr. <maxdemarzi at gmail.com>:
>   > Hello,
>   >
>   > What is the proper way to handle things that have only a few choices
>   like:
>   >
>   > gender (male/female/unknown)
>   > status (active, inactive, purged)
>   > race(10 choices + other)
>   > etc.
>   >
>   > As properties of a Person node, or as nodes that link to the Person
>   node?
>   >
>   > Pros or Cons of each method?
>   It depends on how you're querying the data... gender, status and race
>   could probably be modelled using properties (and maybe indexed with
>   IndexService, see [1]http://components.neo4j.org/neo4j-index/) since
>   you
>   would use them as filters in queries. But if you're planning to do
>   traversals which will bridge persons over to other persons (or other
>   entities) via f.ex. status, then relationships would be handier.
>   >
>   > How about something with instances?
>   >
>   > Student took a Class (twice) once with This teacher, once with
>   Another
>   > Teacher.
>   >
>   > The first time he failed, the second time he got a B.
>   >
>   > Create a StudentClass node with a property of Grade, linked to
>   Teacher?
>   Yes, have each student as a node. Each class instance as a node with
>   TEACHES_IN relationship to teacher (and maybe CLASS_TYPE relationship
>   to what type of class the class instance is). Have a TAKES_CLASS
>   relationship between student and class instance and set grade property
>   on that relationship.
>   >
>   > In order to answer:
>   >
>   > Find all students who took the class.
>   Relationships between student and class.
>   > Find all students who took the class when it was offered in the
>   spring
>   > semester (or taught by This Teacher).
>   Start from either a teacher node (and go to the class instance) or
>   from a class instance. They can be lookup up from and IndexService or
>   something) and get relationships to students from there.
>   > Find all students who got a B
>   If you create nodes for each grade available and create relationships
>   to those grade nodes whenever a student gets a grade. Then it'd be
>   easy to just get that "B" grade node and traverse all its
>   relationships to students. Otherwise you could index the grade
>   property from the ATTEND_CLASS relationships (see above) for the
>   student nodes.
>   > Find all students to got a B in this class?
>   Start from the class and traverse out to all its class instances and
>   students, filtering those who got a B (using the grade property on
>   ATTEND_CLASS relationships).
>   > Find all students to got a B in this class during the spring
>   semester?
>   Same as previous but only traverse those class instances which were
>   offered in spring semester.
>   > Find all students to got a B in this class when This Teacher taught
>   it?
>   Start from either the teacher node or the class node and find the
>   class instance for that class which the teacher has a relationship to.
>   And tou get the students from there.
>   I hope this will help you,
>   Best,
>   Mattias
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> References
>
>   1. http://components.neo4j.org/neo4j-index/
>   2. https://lists.neo4j.org/mailman/listinfo/user
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-- 
Mattias Persson, [mattias at neotechnology.com]
Neo Technology, www.neotechnology.com


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