Hello, Some updates since my last email. We are finding PREMIS to be incredibly helpful with documenting Preservation Metadata. It is also a very helpful guide in terms of what should be documented, and how objects link to one another. I'd like to provide our current use case, followed by some observations on my previous questions in my initial post. Firstly, here are two basic events involved in making a digital representation of a film: Event 1. 35mm combined optical print is scanned to 16-bit TIFF, overscanned to include the combined optical track and perforations. Event 2. Using AEO-Light, a PCM/WAV file is extracted from the TIFFS. Some scanners such as the Blackmagic Cintel use DaVinci Resolve to perform this action. As our preferred post production software only uses DPX, the following basic events are involved in creating a restored version: Event A. The TIFFS created in Event 1 are transcoded losslessly to a new 16-bit DPX sequence via ffmpeg. AVID only allows for a lossy import of the TIFFS, so working with DPX is preferable. Event B. PCM/WAV created in Event 2 is restored in RX5/ProTools creating a new PCM/WAV file. Event C. Colour correction and cropping occurs in AVID/Baselight. Event D. A new DPX sequence and seperate WAV is exported and the 16-bit DPX created in step A is deleted. Event E. In the future, the DPX+WAV may be converted into a single FFV1 image stream in a Matroska container It's an awkward workflow, but our hands are tied. Our 12-bit scanner only has 10-bit options for DPX, so in order to get all 12-bits, we need to use the 16-bit TIFF option. So we create two Representations of the one Intellectual Entity that we intend to preserve : Representation 1 (Events 1 and 2) = Untouched TIFFS straight from the scanner, and the seperate AEO-Light WAV file, which may be converted to FFV1/Matroska. Representation 2 (Events A to E) = Graded/Corrected DPX sequence and a seperate corrected PCM/WAV file, which may be converted to FFV1/Matroska. Here are some updates on each of my 4 questions in the previous email, along with three new questions: 1. After looking more at the definitions of Representations in the PREMIS data dictionary, there seems to be no question that the Representation must be the TIFFS and the WAVS, as the audio and image is required for a complete rendition of the Intellectual Entity. In my current work in progress PREMIS generation script, there is a single Representation object followed by individual file objects for each TIFF and the WAV. 2. This issue is still seems relevant to me. It would seem that some objectCharacteristic information for a representation would be valuable to have, especially overall filesize. The note on fixity information with regards to Representations on page 59 is interesting. It says that this information should be recorded on a file level, as the information is relating to individual files. However, storage information is applicable to representations in PREMIS, but should it also be said that the storage relates to files, rather than representations? 3. In our PREMIS implementation meetings in the IFI, we haven't discussed Events and Agents in as much detail as objects as of yet. I am still curious about the best way to link agents and events to objects. Some events will include: Creation, Message Digest Calculation, Fixity, Deletion, Compression etc. It would seem to be most convenient for the linkingObjectIdentifier to link to the Representation. There are some occasions where an event only relates to either the image sequence or the seperate WAV, but not both. In this case, it would appear best to link on a File level, rather than a Representation level. Only transcoding the image sequence, but not the WAV would also appear to require file level documentation, so would this require one event, with linking identifiers to each file(anywhere from 500 to 150,000 files)? I'm not sure how else to do it. Multiple fixity checks over time would have a massive amount of documentation if recorded on a file level. 4. I think that some sort of fixityExtension could be helpful, but I currently just record checksums for each item in the 1.5.2 fixity semantic unit and keep a seperate manifest file. Perhaps this is already covered in eventOutcomeDetailExtension. 5. I have a new question with regards to the PREMIS v3 documentation. There is a very useful map on page 9 displaying the relationships that objects can have with each other. Looking at that map, there is no arrow pointing from Representation to File. However in the example of relationSubType(1.13.2) on page 120, it looks like a Representation can have a 'has root' relationship with the first file in a sequence. I would assume that the first file could have a reciprocal 'is root of' relationship. Am I correct in thinking that there is a contradiction, or is that map just a visualisation tool showing some of the possible relationships? 6. Another question with regards to documenting complex process histories. In our case, if we want to document every step, we will need to record information about objects that will not actually be preserved. For example, the graded/restored file that ultimately gets sent to preservation storage has been through several events that result in the creation and deletion of new objects. Going back to the previously described workflow involved in restoring the captured TIFFS, the objects created in events A and D are deleted, and their derivatives make their way to preservation storage instead. I am thinking that it makes sense to retain information about these deleted objects on our database. The preserved objects can link back to them so that we can get an unbroken sense of the process history involved in going from film to restored DPX/FFV1. Does this make sense or is there some other way to document this? 7. A question on relationships: The WAV is created from the TIFF sequence, so it has a structural relationship to the TIFFS, and possibly a derivation relationship. It is difficult to map the structural relationship of the WAV to the TIFF when using the recommended LOC relationshipSubTypes. In a sense, they are siblings, as they are both ultimately derived from the same source film. The WAV is actually created from the TIFF, so in this sense, the WAV also appears to have a 'hasSource' relationship to the TIFFs.There are several ways to document all this, but I wonder if some of them end up contradicting the concept of what a representation as defined by PREMIS is. I know that this is a niche use case but perhaps there are similar examples in other fields that could shed some light on our issue? I look forward to discussing all this with the PREMIS community. It would be great if anyone who is already documenting image sequences via PREMIS could post to the thread as well. Best regards, Kieran O'Leary IFI Irish Film Archive P.S - I thought I'd include my initial email underneath... > Hello, I am investigating/experimenting with PREMIS and I am trying to automatically generate xml documents as items pass through our workflows via python scripts. I work in the Irish Film Archive, so we generally handle self-digitised moving image material as well as born digital files. I hope that you can help me with some questions. As we handle very large image sequences (approx 150,000 TIFF/DPX files per film), I'm curious as to how to document these in PREMIS. 1. My main question is if these sequences need to be documented as a representation object for the whole image sequence, and then perhaps each image in the sequence requires their own file object? This would lead to a gigantic xml file, but I see the value in recording this information on a file level. I notice that something similar happens in your 'Animal Antics' example in the v3 documentation. Are there any examples available of an image sequence documented like this? On our regular database, we would view the whole sequence as one object/package, and it would have one database record per sequence. 2. I also notice that objectCharacteristics is not applicable to Representations, so I'm not sure how to document the overall file size of the image sequence? 3. As for events, environments, agents, It would seem to make sense to link all these to the single Representation object. I'd hate the thought of having linking identifiers for all 150k files to a 'capture' event, or even multiple fixity check events over time. Hopefully linking such events to the Representation object is sufficient? 4. Initially I was wondering how to document fixity, as it makes most sense to me to just include a separate checksum manifest within the SIP/AIP. There does not appear to be a method within PREMIS to point to an external file like this for fixity, such as 'fixityExtension'? I suppose that this is only an issue when documenting a representation object that contains multiple files, rather than documenting fixity for a single file. Any help on one or all of the questions would be greatly appreciated. Kindest regards, Kieran O'Leary.