RESTful URLs for non-CRUD operations

A common way of designing a REST system is to recognize the resources and associate a logical hierarchy of URLs to them and perform the traditional CRUD operations by using the well-known HTTP methods (GET, POST, PUT and DELETE).

However, many systems have operations which don't quite fit into the CRUD paradigm. Say, I have a repository of persons. And say I have an id associated with every person which allows me to have nice URLs to each person as such:

http://example.com/persons/1

This URL obviously GETs me the details pertaining to person 1. Now what if I wanted this person to talk and walk. I can think of 3 approaches to designing this scenario:

1. Operations as resources: Which means I can have URLs such as:
   

   http://example.com/persons/1/talk
   http://example.com/persons/1/walk

   However, walk and talk are obviously not resources and designing it this way might be considered unRESTful(?).



2. Operation as a query parameter: This leads to URLs such as:
   

   http://example.com/persons/1?operation=talk
   http://example.com/persons/1?operation=walk

   A drawback of this approach comes to the fore if you need other parameters to perform an operation. So, for instance, if you had to specify what to talk or where to walk. You'll end up with URLs such as these:
   

   http://example.com/persons/1?operation=talk&what=Hello
   http://example.com/persons/1?operation=walk&where=North

   As you can see, with this approach you end up having resources with overloaded operations and parameters. And you have to be aware of these combinations yourself and also explain them to your users.



3. Matrix URIs: Specify the operations using matrix-like URIs. With this, your URLs look as such:
   

   http://example.com/persons/1;talk
   http://example.com/persons/1;walk

   And you can specify the operation parameters using the traditional query string:
   

   http://example.com/persons/1;talk?what=Hello
   http://example.com/persons/1;walk?where=North

   With this approach you have 3 distinct ways of representing 3 different things - slashes (/) for hierarchical resources, semi-colons(;) for operations and query strings (?param1=val1&param2=val2) for parameters.

Although I like the clarity of #3, I haven't seen this approach used all that much. Which makes me reluctant using it myself. Are there any web systems out there that use this approach? Are there any drawbacks to this approach which is why it is not widely employed? Are there any other approaches to designing URLs for operations?

Many questions. Any answers?