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Data Dictionary Workgroup

The RESO Data Dictionary provides a real estate based data standard, both nationally and internationally where applicable, globalizing data fields and lookup values (enumerations) with standard names, data types, and definitions. The RESO Data Dictionary also serves as a common center for the expression of fields and lookup values across various methods of inputting, accessing and transporting real estate data.

The Workgroup’s purpose is to develop, maintain, evolve, and aid in the correct adoption and utilization of the RESO Data Dictionary through the input of subject matter experts including, but not limited to, real estate brokerages, technology companies, Association of REALTORS and Multiple Listing Services. The resulting RESO Data Dictionary is published to the public as an open source standard.

How do I find the Data Dictionary?

The RESO Data Dictionary is a collection of web pages and can be found at: Data Dictionary Home Page. The home page contains links to the most recent Data Dictionary versions and a brief explanation of how to use the Data Dictionary. It also includes an explanation on Data Dictionary Certification with links to additional certification details. The most current Data Dictionary version (as of the time of this writing, June 2021) is Data Dictionary version 1.7.

How is the Data Dictionary Constructed?

The Data Dictionary Wiki is built on a ‘Tree’ structure with its lowest levels comprised of fields and lookup values. The Dictionary can also be downloaded into machine readable XML and a more traditional spreadsheet (.xlsx) layout.

At the Data Dictionary’s highest level, you will find Resources (High level groupings such as Property, Offices, Open Houses, Media, etc.), Collections (A container of data items that have a shared relevance such as Property Rooms, Property Unit Types, etc.) and Lookup Fields and Values (Possible values for Fireplaces, Water Sources, Countries, Buyer Financing, etc.). Drilling down into Resources and Collections you will find fields and within Lookup Fields and Values you will find Lookup Values.

The Data Dictionary also has valuable secondary information to help understand its background, use and context. Some of the most helpful secondary pages are:

On-Going Growth

The Workgroup purpose is to maintain and develop the Dictionary. 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 like 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.
  • 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 are 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.

Thank you for your interest and participation in the Data Dictionary. We invite all MLSs, Brokers and Technology partners to refer to the dictionary as a future center for their own metadata.


The Data Dictionary Workgroup meets the 3rd Thursday of every month at 12:00 pm ET / 9:00 am PT. | JOIN A RESO WORKGROUP!


Data Dictionary Workgroup Chair – Rob Larson

Rob is currently the Managing Member at Larson Consulting LLC and a Director for Build it Green. He has also  been involved with RESO/RETS since 2004.






Data Dictionary Workgroup Vice-Chair – Kevin Tranby, RESO Compliance Manager, FBS

One of FBS’s longest tenured employees, Kevin Tranby’s affinity for industry standards began in 1987 when his days were spent printing MLS books. Now the RESO Compliance Manager at FBS, Kevin has been a member of the Data Dictionary Workgroup since 2015.

Beyond data standards, Kevin enjoys spending time with his family and serving the Nights of Columbus, where he has held numerous offices at the local and state level.