Post Vs Put

According to RFC 2616

The POST method is used to request that the origin server accept the entity enclosed in the request as a new subordinate of the resource identified by the Request-URI in the Request-Line. […] The actual function performed by the POST method is determined by the server and is usually dependent on the Request-URI. The posted entity is subordinate to that URI in the same way that a file is subordinate to a directory containing it, a news article is subordinate to a newsgroup to which it is posted, or a record is subordinate to a database.

PUT is defined as:

The PUT method requests that the enclosed entity be stored under the supplied Request-URI. If the Request-URI refers to an already existing resource, the enclosed entity SHOULD be considered as a modified version of the one residing on the origin server. If the Request-URI does not point to an existing resource, and that URI is capable of being defined as a new resource by the requesting user agent, the origin server can create the resource with that URI.

See this for a discussion. What eventually i am going with is this understanding:

This is specified in RFC 2616 §9.5ff.POST creates a child resource, so POST to /items creates a resources that lives under the/items resource. Eg. /items/1PUT is for creating or updating something with a known URL.
Therefore PUT is only a candidate for CREATE where you already know the url before the resource is created. Eg. /blogs/nigel/entry/when_to_use_post_vs_put as the title is used as the resource key