TYPO3 Core

Having an identifier independent to the UID, makes it easier to deal with multiple systems (dev,live,...) which have different records.

Currently backend_layouts are used mostly with

10 = FLUIDTEMPLATE
10 {
    file.stdWrap.cObject = CASE
    file.stdWrap.cObject {
        key.data = levelfield:-1, backend_layout_next_level, slide
        key.override.field = backend_layout

        default = TEXT
        default.value = EXT:fo/Resources/Private/Templates/Page/modern_3col.html
        2 = TEXT
        2.value = EXT:fo/Resources/Private/Templates/Page/modern_2col.html
    }
    layoutRootPath = EXT:fo/Resources/Private/Templates/Page/Layouts/
}

but this makes it hard because the UID of the layout will be different

having an identifier would make it a lot easier, like

10 = FLUIDTEMPLATE
10 {
    file.stdWrap.cObject = RECORDS
    file.stdWrap.cObject {
        tables = backend_layout
        source {
            data = levelfield:-1, backend_layout_next_level, slide
            override.field = backend_layout
        }
        conf.backend_layout = TEXT
        conf.backend_layout {
            value = EXT:fo/Resources/Private/Templates/Page/{identifier}.html
            insertData = 1
        }
    }
    layoutRootPath = EXT:fo/Resources/Private/Templates/Page/Layouts/
}

of course you could still use cObj CASE and use the field identifier as key there.