JSContact Version 2.0: Optional Unique Identifiers

Notational Conventions 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 BCP 14 when, and only when, they appear in all capitals, as shown here. The ABNF definitions in this document use the notations of . ABNF rules not defined in this document are defined in either (such as the ABNF for CRLF, WSP, DQUOTE, VCHAR, ALPHA, and DIGIT) or .

Introduction defines the "uid" property of a Card object, a mandatory property which contains an unique identifier for the entity represented by that contact card. This property being mandatory has shown to be applicable for some use cases, but has turned out to be an issue in other contexts. For example, the CardDAV protocol requires the UID property of a vCard object to be set. Accordingly, an internet server that implements both CardDAV and JMAP for Contacts requires the "uid" property of a JSContact Card to be set. In contrast, protocols such as RDAP have no use for the "uid" property, either because they use different identifiers, or they prefer to not include any unique identifier in the contact data at all. JSContact should not require them to generate unique identifiers that are irrelevant to their use case. Also, one of the stated goals of JSContact is to be compatible with the semantics of the vCard data format (). But defines the UID property of a vCard to be optional, and consequently the semantics of JSContact and vCard differ for such a crucial common element. In case of vCards without a UID property being converted to JSContact, requiring unique identifiers is especially problematic: the Card "uid" property is mandatory and accordingly requires implementations to generate some unique identifier for it during conversion, but it does not guarantee it to be the same across implementations or even one implementation converting the same Card multiple times. A recipient being unaware that the "uid" property value of such a Card object is ephemeral might refer to it in the "members" or "relatedTo" properties of another Card object, introducing invalid relations between contact cards.

JSContact Version 2.0 This document redefines the "uid" property of a Card object to become optional. Other than that, the property definition is left unchanged. This change requires the major version of JSContact to change, so this document defines the JSContact version to become "2.0". Implementations MUST create JSContact data according to version "2.0" and MUST set the "version" property of newly created Card objects to "2.0" (or higher). They MUST validate JSContact data according to version "2.0", that is, they MUST NOT reject a Card object without the "uid" property as invalid unless specified differently. As any version "1.0" JSContact Card also is valid according to version "2.0", there is no need to migrate existing JSContact data. If to set the "uid" property is use-case specific. If an implementation is able to consistently generate the exact same unique identifier for a JSContact Card representing the same entity and no protocol-specific concerns prevail, it is recommended to set the "uid" property.

Redefined "uid" Property This document redefines the type signature of the "uid" property, originally defined in . The new type signature is:

uid: String (optional).

The remaining property definition is left unchanged, with the following additional paragraph: A Card without a uid property can not be referred to as group member in the "members" property, or put in relation to another Card object in the "relatedTo" property.

Redefined Conversion Rule for the "uid" Property This document redefines how to convert the Card "uid" property from vCard, originally defined in . The new conversion rule is: Implementations that convert a vCard without a UID property to a Card of version "2.0" or higher MUST NOT generate a unique identifier as value for the "uid" property. When converting a vCard without UID property to obsoleted JSContact version "1.0", implementations MUST generate a value for the "uid" property. Generating unique identifiers is implementation-specific. An implementation SHOULD generate the same value when generating the same Card multiple times, but MAY generate different values for each conversion. describes why this is problematic. Consequently, implementations SHOULD NOT convert to version "1.0" Card objects.

IANA Considerations

Update to the JSContact Version Registry IANA will update the "JSContact Version" registry, originally created in . It will add the following record: JSContact Version Registry

Major Version	Highest Minor Version	Reference
2	0	This document

Update to the JSContact Properties Registry IANA will update the "JSContact Properties" registry, originally created in : For the "Reference/Description" column of the "uid" property, it will replace the reference to with a reference to of this document.

Security Considerations This document does not provide new security considerations. The security considerations of apply.