Load DDS from metadata spreadsheet

[swhume]

Load the DDS metadata template from one of the widely used metadata spreadsheets. The purpose is to enable organizations that are not yet using USDM and BCs to adopt this define-xml generation program, embracing today's approach to generating define-xml alongside the new approach.

[swhume]

The metadata spreadsheet referenced here is something similar to what organizations use today to generate a Define-XML, for example, using P21. These spreadsheets have tabs like: Study, Standards, Datasets, variables, valueLevel, WhereClauses, CodeLists, Dictionaries, Methods, Comments, and Documents.

[mikemolter]

Currently in the middle of processing metadata from one particular Excel format. Have posted some questions in Slack around the proper json format. Aiming to have a first draft (for this Excel format) complete by April 20, at which point I'll do a pull request.