Best practice for many-to-many relationship between content tree items?

In my content tree, I have a tree of content items which represent cities. For each of those I want to have logical connections to a set of... let's say... National Parks that are within 2 hours driving distance. So a city will have multiple parks... and each set will be different... but of course a park will also be associated with more than one city.

What kind of Item and field setup works well for this sort of situation? I will be creating a custom renderer for these items, so I'm mostly concerned with how this should look in Sitecore to maximize ease of use and开发者_开发知识库 performance.

I'm using Sitecore 6.2.

(cross-posting from SDN, please forgive me... but I want to encourage more Sitecore community here on StackOverflow)

For this kind of relationship you'll need the following structure:

Home

   Cities

       NY
       London
       Paris

   Parks

       Park1
       Park2
       Park3

The "City" template should have the Multilist type field called "Parks". The soulrce of this field should look to the root of Parks (Home > Parks). The same way the "Park" template has the Multilist field called "Cities". The source of this field should look to the root of Cities (Home > Cities).

In this way you'll be easily able to perform any kind of request.

Hope this helps.

If the connection has to be both ways one way you could handle it is by adding some code to the save event.

Let's assume we have a City template with a field called "Related Parks", and a Park template with a "Related Cities" field.

Say we save a City item with two parks in the "Related Parks" field. On the save event we could retrieve the two parks and insert the current city being saved into the "Related Cities" field on those parks.

I am not necessarily saying this is the best way to go about it, just another option.

Are you going to be doing any lookups from park to city? For instance, would you need to say "find all the cities that are associated with a given park"? Or will it just be "find all the parks that are associated with a given city"? If you need to do the lookups in both directions, things get a little trickier and I would probably recommend using a search index. However, if your lookup is only in one direction, you could just use a treelist field to make associations from one item to many others.

From your description I'm not entirely sure if you actually need to use that many-to-many relationship, or if a one-to-many path is all you need?