Real Estate Standards Organization (RESO) J. Darnell, S. DeBord Request for Comments: xxxx RESO Category: Informational December 2020 A URN Namespace for RESO Status of this Memo This document is intended to be informational for the internet community. The examples provided are non-normative at this point and RESO may continue to add additional identifiers or change what's outlined here at a future time, where appropriate. Abstract This document describes a Uniform Resource Name (URN) namespace to be used by the Real Estate Standards Organization (RESO) for the naming of items in RESO's standard metadata catalog, for identifying unique licensees and organizations acting as as recorders in real estate transactions within a decentralized network, and for the creation of unique property identifiers for real property and related assets. Copyright Notice Copyright (c) Real Estate Standards Organization (RESO). All rights reserved. 1. Introduction The Real Estate Standards Organization (RESO) produces metadata catalogs, domain-specific models, and data transport standards for use by real estate transaction processors as well as data producers and consumers. During the recording of transactions, various identifiers are used that originate from many different organizations and participants, both licensed and unlicensed, in various formats which involve RESO standard metadata items and their state at a given point of time. The primary goal of the 'reso' URN is to ensure that RESO standard data elements are identified within the transaction in a manner that provides consistent representations of participant and metadata identifiers. 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 3. Specification Template 3.1 Namespace ID: "reso" 3.2 Registration Information: Version: 1 Date: 2020-12-22 3.3 Registrant of the Namespace Registering Organization: RESO Designated Contact: info&reso.org 3.4 Syntactic Structure At the time of publication, URNs that use the 'reso' NID SHOULD have one of the following structures: 3.4.1 RESO Data Dictionary Metadata Elements (a) Versioned Metadata Resource Element Format: urn:reso:metadata:{version}:resource:{resource-name} where "version" MAY have values such as "1.6" or "1.7", and "resource-name¨ is one of "Property", "Member", "Office", or other resource definitions RESO provides (see references). Example: urn:reso:metadata:1.7:resource:property (b) Versioned Metadata Field Element Format: urn:reso:metadata:{version}:resource:{resource-name}:field:{field-name} where "version" MAY have values such as "1.6" or "1.7", "resource-name" is a defined resource, and "field-name" is a defined data field in the domain. Example: urn:reso:metadata:1.7:resource:property:field:listprice (c) Field Metadata Element using Record Identifier Format: urn:reso:metadata:rid:{rid} where "rid" is a version-independent field metadata identifier assigned by RESO and unique within its domain. Example: urn:reso:metadata:rid:100311 where rid 100311 is the "AboveGradeFinishedArea" field in RESO's Data Dictionary metadata catalog. (d) Lookup Field Metadata Element using Lookup Field Identifier Format: urn:reso:metadata:lfid:{lookup-field-id} where "lfid" is a version-independent lookup value metadata identifier assigned by RESO and unique within its domain. Example: urn:reso:metadata:lfid:301001 Lookup fields are used to group related collections of allowed field values. For example, "StandardStatus" can have a value of "Active" or "Active Under Contract" and its lfid is 301001. (e) Lookup Metadata Element using Lookup Identifier Format: urn:reso:metadata:lid:{lookup-id} where "lid" is a version-independent lookup value metadata identifier assigned by RESO and unique within its domain. Example: urn:reso:metadata:lid:301002 Lookups values are to uniquely represent standard enumerated values that are available for use within a given lookup field. For example, "Active Under Contract" has a lid of 301002. 3.4.2 RESO Universal Property Identifier (UPI) Format: urn:reso:upi:{upi} where "upi" is the RESO Universal Property Identifier (UPI) for a given property. The RESO UPI is a standard format that encodes Country, State (FIPS), County (FIPS), Subcounty (FIPS), the parcel number, property type, and optional sub-property type in order to identify unique real properties. If two UPIs are constructed from the same underlying data using the RESO UPI standard, then the same identifier will be produced across disparate systems even if they don't exchange the underlying data. Example: urn:reso:upi:us-06037-n-abracanet-r-n For more information about the RESO UPI, see section 5.2. 3.4.3 RESO Unique Licensee Identifier (ULI) Format: urn:reso:uli:{uli} where "uli" is a globally unique licensee identifier within the RESO domain. RESO is constructing a licensee identifier standard and resolution protocol in order to assign a globally unique and immutable identifier to any participant in a transaction. This could be a real estate agent, broker, transaction coordinator, assessor, photographer, and others not specified here. Example: urn:reso:uli:123e4567-e89b-12d3-a456-426652340000 where 123e4567-e89b-12d3-a456-426652340000 is a unique identifier for a given licensee. 3.4.4 RESO Unique Organization Identifier (UOI) Format: urn:reso:uoi:{uoi} where "uoi" is a globally unique organization identifier within the RESO domain. RESO assigns Unique Organization Identifiers within its domain to represent well-known organizations that exist as participants in the real estate transaction. Example: urn:reso:uoi:2352675 where 2352675 is a unique identifier for a given organization. 3.4.5 Event Subjects and Recorders in RESO's standard Event Model (a) Event Model Subject Identifiers Format: urn:reso:metadata:1.7:resource:{resource-name}:field:{field-name}:{value} urn:reso:metadata:1.7:rid:{rid}:{value} These are used to represent the subject in the recording of a transaction and MAY have several different formats that build on previous metadata URNs by also providing a value: Examples: urn:reso:metadata:1.7:resource:property:field:listingkey:abc123 urn:reso:metadata:1.7:resource:member:field:memberkey:z12345 urn:reso:metadata:1.7:rid:12385:3400000 urn:reso:upi:us-06037-n-abracanet-r-n (b) Event Model Recorder Identifiers Format: urn:reso:uoi:{uoi} As outlined in 3.4.4, RESO issues unique identifiers to be used by well-known organizations that participate in the real estate transaction. 4. Security Considerations This document introduces no additional security considerations beyond those associated with the use and resolution of URNs in general. 5. References 5.1 Normative References [RFC2141] Moats, R., "URN Syntax", RFC 2141, May 1997. 5.2 Informative References [https://ddwiki.reso.org/display/DDW17] RESO Data Dictionary 1.7 Wiki, January 2018. [https://www.reso.org/universal-property-identifier/] RESO Universal Property Identifier (UPI), Dec 2017.