About Unique Identifiers


It is important to have identifiers assigned to each individual item before any digitization is started. An identifier is simply a number that is unique within the collection (the way that a person has a unique Social Security Number). It might be as simple as numbering items from 1 to the number of items that you have, or you may already have numbers assigned to your items (see the section below). Since we do not know your items as well as you do, having numbers gives us a way to know which item we’re talking about throughout the process as we digitize items. If you are scanning your own items, identifiers give you a way to track items the same way that we do and gives us a way to discuss a specific item with you after we receive your images. (For more information about using identifiers if you are scanning your own items, see this section on the About Scanning Your Materials page.)

How Identifiers are Used

The unique identifiers are used to track items as they go through each stage of digitization:

  • checking physical items into the Lab
  • naming files when items are scanned
  • adding identifiers to the metadata records
  • finding the physical items if we need to compare them to the digital images
  • checking physical items out of the Lab
  • using identifiers in the metadata to find digital images after they’re uploaded

Because we use identifiers in so many ways, we sometimes make minor modifications to the identifiers that you give us, for example:

  • We add your institution code to the front of identifiers that are locally-assigned (we generate the institution codes in-house when we start your project)
  • If your identifiers include periods (.) we change them to dashes (-) for use in file names
Your Original Identifier Identifier Used for File-naming Identifier Used in Metadata
B650 ELPL_B650 ELPL_B650
76-085.071 PBPM_76-085-071 PBPM_76-085.071*
0001 ABCD_0001 ABCD_0001

*Note: if we are creating metadata for your items, we generally use the file-naming identifier (e.g., PBPM_76-085-071) instead of the original identifier unless you request that we use the original (you can use the Metadata Request Form for that).

Since unique identifiers are meant for identification rather than for description, we prefer that assigned identifiers be numbers or alpha-numeric codes rather than words or phrases. When we track items through the digitization process, identifiers with a standardized format (similar to the examples above) are the easiest to sort as digital files and to match with physical copies when necessary.

If Your Items Already Have Unique Identifiers

You don’t have to create new identifiers if your items already have identifiers. Some examples of identifiers your items may have that will work:

  • accession numbers
  • barcodes
  • OCLC numbers
  • LCCNs
  • library catalog numbers (bibliographic record numbers)

There are two things to keep in mind if you plan to use established identifiers:

1. You may need to change your identifiers or assign new ones if:

  • they contain special characters
  • they contain periods (see above)
  • they are particularly long or unwieldy

2. Sometimes established identifiers may not be unique, for example:

  • photographs kept together in a sleeve
  • related items listed in a single catalog record

It is important to check for this and to make sure every individual item has a separate number

If Your Items Do Not Have Unique Identifiers

If your items do not already have identifiers, you’ll need to add an identifier to each individual item.

  • the easiest way to add identifiers is to number 1 through the total number of items you have (e.g. 1-200)
  • add zeroes to the beginning of numbers so that they will sort properly
    • use four digits if you have 1-999 items (e.g., 0001, 0010, 0100, etc.)
    • use five digits if you have 1-9999 items (e.g., 00001, 00010, 00100, 01000, etc.)
  • an item is a single object (a book or document with multiple pages is still a single object)

If you are concerned about easily finding digital files later, it may be useful to keep a spreadsheet or table that lists the identifiers you assign and a corresponding title or keywords. Also keep in mind that the identifiers you assign at the start of the project will be in the records for each item when they go online, so you will have a way to search for an item and match it to the appropriate identifier in the digital files.