Data Dictionary

What is the Data Dictionary? It's Real Estate's "Rosetta Stone"

The Data Dictionary serves as the real estate industry’s “Rosetta Stone” for real estate data. Hundreds of MLS, and other source providers, gather data. But what good is it if the data cannot be shared or understood? The Data Dictionary ensures that each system “speaks” the same language. It is the common standard that defines real estate data in consistent terms and data structures; a template data providers may follow to format its most common fields.

The RESO Dictionary has two purposes.

  1. Serve as a non-RETS guideline for a national standard for the fields and look-ups (enumerations) in the MLS.
  2. Common center for all expressions of fields and enumerations.

As an MLS reviews change, it is advised to consider the benefits of growing closer to the national standard. Not only will it make the effort of ensuring RESO compliance easier, it will also ensure that as listings progress through IDX and other aggregation points, the meaning of your data is not diluted or misinterpreted.

The Data Dictionary is broken down into the following tabs. Please review the following details and information on use of the dictionary.

  • Meta-Definitions: This page should be reviewed first. It contains the definitions about the fields used in the RESO Dictionary to define the fields and look-ups.
  • Recommendations: List of suggested Data Dictionary changes including discussion notes.
  • RESO Dictionary: Each Data Dictionary resource will have its own tab containing fields and their defining details. Dictionary tabs include: Property, Member, Office, Media and History.
  • Enumerations: This tab has the list of enumerations, or pick lists, that have been defined thus far. Keep in mind, that unless "locked" all lists are extensible.
  • Deleted Elements: These are fields or enumerations that have been deleted from the dictionary.

An MLS will probably use a subset of the Data Dictionary, as not all Data Dictionary fields apply to every MLS.

Data Dictionary Certification

RESO Data Dictionary Certification is awarded to data providers that conform to current RESO Data Dictionary Standards.

The RESO Data Dictionary Certification process is described in the following document (PDF): Data Dictionary Overview v1.0.3. A glossary (PDF) of common terms is also available. 

The “RESO Data Dictionary Certification Testing Rules v1.0.3” contains the RESO Data Dictionary Certification requirements.

These documents should be read by any organization who wants:

  • To learn more about the Data Dictionary and its benefits;
  • To create a Data Dictionary compliant data structure; and
  • To have an understanding of the certification process.

Not all information required to evaluate a Data Dictionary application can be submitted through an online form. Filling out the Supplemental Application Information (SAI v1.3) spreadsheet will provide the RESO Compliance Department with the required information. Please refer to the “Instructions” on the first tab of the linked spreadsheet for more information.

Please email with any questions.

Benefits of Data Dictionary Implementation

Simplified Data Integration: Data Dictionary structured data can move between systems without losing information; Data translation costs are reduced because of consistent data definitions and usage; and it is easier for MLS’s, vendors and other third parties to develop new, data-driven applications and services that serve Realtors® across North America.

Quality Stamp of Approval: RESO Certification provides 3rd Party Verification of your client’s functionality based on professional industry-wide standards.

Simplified Marketing: “RESO Certified Data Dictionary” says all you need to say about the interoperability of your online real estate information.

Promote support for Standards: Those receiving a RESO Certification may display the RESO Certified Logo on their website.

Getting Started with the Data Dictionary Implementation & Migration Starter Kit for MLSs (1.3) 

RESO created a Data Dictionary Implementation & Migration Starter Kit for MLSs to help those Data Providers and MLS seeking Data Dictionary Certification.  The starter kit provides recommended steps and a link to a mapping template.

The mapping template is a spreadsheet that helps applicants match their current data structure with the Data Dictionary.  A filled-out template should help identify the changes required to be fully compliant.

RESO staff are here to help anyone through the mapping and certification process. Please send all questions to

DLU 07.28.2015


Data Dictionary Certification

Click here to apply for a Data Dictionary Certificate.

Data Dictionary Downloads

Version 1.4

Version 1.3

Data Dictionary 1.3 Core Fields

Version 1.2

Version 1.1

Version 1.0


Click here to access additional information on the Data Dictionary Workgroup.

powered by MemberClicks