2010/2/19 <[email protected]>: > 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 <[email protected]> > Date: Fri, February 19, 2010 4:27 am > To: Neo user discussions <[email protected]> > 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. <[email protected]>: > > 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 > _______________________________________________ > Neo mailing list > [email protected] > [2]https://lists.neo4j.org/mailman/listinfo/user > > References > > 1. http://components.neo4j.org/neo4j-index/ > 2. https://lists.neo4j.org/mailman/listinfo/user > _______________________________________________ > Neo mailing list > [email protected] > https://lists.neo4j.org/mailman/listinfo/user > -- Mattias Persson, [[email protected]] Neo Technology, www.neotechnology.com _______________________________________________ Neo mailing list [email protected] https://lists.neo4j.org/mailman/listinfo/user
