A flag indicating whether an `id` match is allowed is added to each report by [`add_match_id.R`](https://git.noc.ac.uk/brecinosrivas/icoads.utils/-/blob/master/R/add_match_id.R). Generic `id`'s (e.g. blank, "SHIP", "MASKSTID") are allowed to match within a `dck`. Table 8 of the [technical report](https://git.noc.ac.uk/brecinosrivas/icoads-r-hostace/-/blob/master/docs/C3S_D311a_Lot2.dup_doc_v3.pdf) contains the information used to decide whether `id`'s in a pair are allowed to match.

These criteria have been developed by inspection of the
paired `id`'s and are therefore likely to be approximate. 


Damerau–Levenshtein (DL) distance is the number of insertions, deletions and swaps necessary to convert one string to another ([Van der Loo M, 2014](https://journal.r-project.org/archive/2014-1/loo.pdf)). A substring is where one ID is contained within the other. Italics represents the “`id` type”.


References
-----
[Van der Loo M (2014)](https://journal.r-project.org/archive/2014-1/loo.pdf). The stringdist package for approximate string matching. The R Journal, 6, 111-122. <br>
 https://CRAN.R-project.org/package=stringdist.