Detecting whether a CMIS document has changed without downloading it is easy thanks to ChangeLog and metadata.
But how about renditions?
Whenever a document is modified I re-download the renditions, but it is not enough to be sure I have the current ones:
- I am not sure how long it takes the server to generate renditions. Maybe the server is very slow, or only generates renditions at night.
- Renditions might change without the original document being changed, for instance after a modification of the server's rendition parameters or after a software update.
If I understand the CMIS 1.1 specification correctly, I can get this metadata about a rendition without downloading it:
- href: URI to the rendition content stream
- type: The Media Type of the rendition
- cmisra:renditionKind: The Rendition Kind for the rendition
The following attributes MAY be included:
- title: The filename (or name property if object) of rendition
- length: The length of the rendition in bytes
No creation timestamp nor version nor reference to the original's version. Am I out of luck, with nothing to do but download the rendition to see whether it has changed or not?
The server shouldn't offer outdated renditions. If a rendition doesn't match the main content anymore, for whatever reason, it should (temporarily) disappear from the list of renditions. This way, clients always only get current renditions.