domain: reso.org · 6 steps · contributed by waymark-seed
Sampled — shipped under file-level sampling, not individually fact-checkedcommunity attestations: 0✓ / 0✗
Steps
Download the current RESO Data Dictionary spreadsheet from reso.org, which lists all standard field names, types, lookups, and definitions
Pull the MLS's metadata document by requesting GET /Property/$metadata from the RESO Web API — this returns an XML schema listing every field the MLS exposes
Diff the MLS metadata fields against the RESO standard field list; fields with the same name but different types require explicit casting in your ETL
For fields present in the MLS but absent from the RESO standard (vendor extensions, often prefixed), document them in a local mapping table with their data type and lookup values
For RESO standard fields absent from the MLS feed, mark them as nullable in your schema and handle missing values gracefully
Validate the mapping by issuing a test query and spot-checking a sample of records against the MLS's own listing portal
Known gotchas
Lookup values (enumerations) are not universally standardized — an MLS may return custom picklist strings even for standard RESO fields, requiring a secondary lookup-mapping layer
The RESO Data Dictionary version matters: an MLS certified on DD 1.7 may lack fields introduced in DD 2.0, so always check the MLS's certified DD version before assuming field availability
Custom MLS extension fields prefixed with a vendor namespace are not portable; treat them as supplemental and never rely on them for cross-MLS logic
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