When I wrote Data::Pairs (http://search.cpan.org/dist/Data-Pairs/), I had JSONified MARC in mind. To my mind, a data structure that is a "Pairs of Pairs"[2] would faithfully represent a MARC record, including preserving the orders of fields/subfields.
Below is the short example from [1] displayed as a Pairs of Pairs in JSON. In Data::Pairs, I wanted to see what the algorithms might be for setting and getting data from such a structure, with the intention that those algorithms might be the basis for a similar JSON library. So my real world situation isn't that I've used any MARC in JSON to date, but I did begin writing code with that intention. :-) Appearing after the JSON example below is the same data displayed as YAML. By taking the Pairs of Pairs approach, I had envisioned that presenting the YAML version to a human might facilitate manual edits. I guess I'm late in the game suggesting another proposal, but there it is. Writing a schema for this might be tricky, but as a data structure it's fairly simple and self-consistent. Regards, Brad [1] http://robotlibrarian.billdueber.com/new-interest-in-marc-hash-json/ [2] http://yaml.org/type/pairs.html JSON: [ { "leader" : "leader string" }, { "001" : "001 value" }, { "002" : "002 value" }, { "010" : [ { "ind1": " " }, { "ind2": " " }, { "a" : "68009499" } ] } { "035" : [ { "ind1": " " }, { "ind2": " " }, { "a" : "(RLIN)MIUG0000733-B" }, ] } { "035" : [ { "ind1": " " }, { "ind2": " " }, { "a" : "(CaOTULAS)159818014" }, ] } { "245" : [ { "ind1": "1" }, { "ind2": "0" }, { "a" : "Capitalism, primitive and modern;" }, { "b" : "some aspects of Tolai economic growth" }, { "c" : "[by] T. Scarlett Epstein." } ] } ] YAML: - leader: "leader string" - 001: "001 value" - 002: "002 value" - 010: - ind1: " " - ind2: " " - a: "68009499: - 035: - ind1: " " - ind2: " " - a: "(RLIN)MIUG0000733-B" - 035: - ind1: " " - ind2: " " - a: "(CaOTULAS)159818014" - 245: - ind1: "1" - ind2: "0" - a: "Capitalism, primitive and modern;" - b: "some aspects of Tolai economic growth" - c: "[by] T. Scarlett Epstein."