15. A content management system, comprising: one or more processors; and a computer-readable medium including one or more sequences of instructions that, when executed by the one or more processors, causes: receiving a first message from a collaboration system remote from a content management system, the first message including document metadata corresponding to a document generated by the content management system and stored therein; synchronizing the first reference to the document with a first client device, such that the first reference is stored via a local file system managed by the first client as a first local reference to the document; mapping the first reference in the content management system to the first local reference in the first client device; in response to receiving the first message, creating, in the content management system, a first reference to the document of the collaboration system and saving the document metadata received in the first message as metadata for the first reference; synchronizing the first reference metadata with the first client device detecting a second reference to the document in the collaboration system as a result of the first client device sharing the first local reference with a second client device; updating the mapping between the first reference and the first local reference, such that the second reference is stored via a second local file system managed by the second client as a second local reference to the document; and upon detecting a change by the first client device to the first reference to the document, synchronizing the change with the second local reference to the document.
15. A content management system, comprising: one or more processors; and a computer-readable medium including one or more sequences of instructions that, when executed by the one or more processors, causes: receiving a first message from a collaboration system remote from a content management system, the first message including document metadata corresponding to a document generated by the content management system and stored therein; synchronizing the first reference to the document with a first client device, such that the first reference is stored via a local file system managed by the first client as a first local reference to the document; mapping the first reference in the content management system to the first local reference in the first client device; in response to receiving the first message, creating, in the content management system, a first reference to the document of the collaboration system and saving the document metadata received in the first message as metadata for the first reference; synchronizing the first reference metadata with the first client device detecting a second reference to the document in the collaboration system as a result of the first client device sharing the first local reference with a second client device; updating the mapping between the first reference and the first local reference, such that the second reference is stored via a second local file system managed by the second client as a second local reference to the document; and upon detecting a change by the first client device to the first reference to the document, synchronizing the change with the second local reference to the document. 19. The content management system of claim 15 , wherein the instructions cause: receiving, from a first user device, a second message including metadata corresponding to the first reference managed by the content management system; updating metadata corresponding to the first reference managed by the content management system based on the metadata in the message; and sending a third message including a document identifier for the document in the collaboration system corresponding to the first reference and the reference metadata, where the collaboration system updates metadata for the document in the collaboration system corresponding to the identifier based on the metadata received in the third message.