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Data Dictionary Version: 1.5  

Welcome to the RESO Data Dictionary 1.5. The RESO Dictionary has two purposes. First is to serve as a common center for expressions of fields and lookups (enumerations) found in a RESO Certified data source.  The second is a universal guideline for the fields and lookups found in an MLS's Listing Input Module. The Data Dictionary 1.5 Approval Date was June 21, 2016.

As an MLS works toward implementing the RESO Data Dictionary, they are advised to consider the benefits of growing closer to the RESO national standards not only in their RESO standards based services, but in their MLS input form as well. Not only will it make the adoption of RESO standards and delivery of their RESO services easier, as listings move from your system to IDX, VOW and other approved systems, it will help to ensure that the meaning of your data is not diluted or misinterpreted. When your members see the same names and terminology around the data in those external services, it will bring an all important consistency to your membership and to their clients who often see MLS reports and displays.

As the RESO Standards have grown, it has become clear that a "common ground" for fields and enumerations is needed. Keeping a centralized method of expressing property and listing concepts will mitigate implementation errors, ease field mapping and foster innovation around a more stable and cost effective center. These benefits can be achieved by implementing the RESO Dictionary in your services. For those who are wanting to minimize the changes to their MLS database (and input forms) there are technological ways to deliver RESO compliant metadata while minimizing change in the MLS input form.

The best way to start using this Wiki is to review Using the Data Dictionary Wiki (1.5) then follow the appropriate links. 

On Going Growth
The RESO Dictionary is designed to grow with our industry. If you have ideas for the dictionary we welcome them. However your ideas for change do require some accompanying information.

Name: Please review fields or enumerations and create a name you feel best fits the current convention.

Definition: We ask that you write a robust definition of the field.

Data Type: Include your recommended data type and maximum field length.

Lookups/Enumerations: If your recommended field is a pick-list, please include enumerations. Enumerations will also need a robust definition.

Justification: Please give a reason the field is important to your market. Also if the field has legal or MLS rules requirements, be sure to include a reference back to the law or rules in question.

Utilization: We ask that you include an indication of how much use your field or enumeration sees. This should be done by a count of the number of listings using the field or enumeration and the number of listings in your sample. This will be used to create a percentage of utilization. Include the criteria used to determine the sample of listings used.

Duplication: Review the dictionary thoroughly to ensure you are not duplicating an already existing field or enumeration. Concepts can be expressed in a number of ways and rather than adding additional fields or enumerations, alternate names are added to the synonym column (and used to improve definition).

Thank you for your interest and participation in the  RESO Data Dictionary. More information will be following form RESO about implementing the Dictionary in existing and future versions of RETS. We also invite all MLSs to refer to the dictionary as a future center for their own metadata (field/enumeration) change decisions.

Please send any questions and/or suggestions to RESO by emailing If you are not already a RESO member, please consider the benefits of becoming a Member of RESO. Go to for more information on how you can participate in RESO.

Note to Mobile Users

It is best for mobile users to view our wiki in 'Desktop Site' mode. This applies to Chrome, Safari, Firefox and other mobile browsers.  If the left navigation pane is not visible, then scrolling down to the section labeled 'Child Pages' will give you similar options.


Page Revision Date: Aug 12 2016