REST collections, good practice to do: GET api/CollectionA/<collection id>/CollectionB?

Question

I need to be able to grab a collection based on a collection of objects. For this, I'm considering a couple of approaches, but am not sure which one makes the most sense, so I'll post them both. If there is a better way that I may not have considered, then please feel free to post your suggestion(s) :)

For example, I'll use Products and Reviews (which are reviews of products) as resources.

Objective: We want to get the Reviews for all of the Products

Approach A:

POST api/Products { json: filters, limits, etc } // returns api/Products/<id>
GET api/Products/<id>/Reviews { json: filters, limits, etc } // returns json array 
// ... of reviews present in products
// id in this case would refer to the collection, which would be cached

Approach B:

GET api/Reviews { json: filters } // returns json array of reviews, but needs to 
// ... have either all of the product ids passed as an array (not practical with 
// ... huge collections), or needs to have all of the api/Products filters passed, 
// ... in which case making the code unDRY

Approach C:

GET api/Reviews { json: filters: { products: 'api/Products?filters' }...
// is this reasonable?

Thanks in advance for any help, and apologies if this question is noob, I'm still new to REST

Approach D:

access individual products
GET api/Product/<id>

access collection of products:
POST api/Products?filters=stuff..
GET api/Products/<id>

access collection of products' reviews

POST api/Products/<id>/Reviews?filters=stuff
GET api/Products/<id>/Reviews/<id>

... this would thus allow us to cache the result easily, does this seem reasonable to you? 

Answer 1

Objective: We want to get the Reviews for all of the Products

Basically, GET /api/products/<id> should return a product, and GET /api/products/<id>/reviews should return all reviews for a given product.

If you want to fetch all products, you will use GET /api/products. As you consider both reviews and products as resources, I recommend you to expose all reviews:

GET /api/reviews

But you probably want products with their reviews. That would mean fetching some products using /api/products (and a set of filters for example) and expanding the result set with reviews. This expand term comes from the OData protocol: http://www.odata.org/documentation/uri-conventions#ExpandSystemQueryOption.

You could do:

GET /api/products?$expand=reviews

GET /api/products?filter=foo&$expand=reviews

This URI means: "identifies the collection of products as well as each of the reviews associated with each product.