This article is a technical explanation and implementation example generated using AI. The code and procedures presented are based on primary sources, but have not been verified on actual devices by the author. Behavior may vary depending on the environment and version. Based on the specifications of RFC 10050 (Protocol-Specific Profiles for JSContact), this article explains the profile structures and registry mechanisms for safely and practically handling limited contact information (JSContact). Rather than exhaustive data exchange, it clearly outlines the design principles for subset definitions tailored to specific protocol requirements and the decision rules for supported properties.
Objective
The objective of this document is to interpret the concept and message structure of the "JSContact Profile" defined in RFC 10050, and to organize which properties and restrictions apply according to protocol-specific requirements. It breaks down the specifications and rules of the IANA registry shown in primary sources to clarify the design approach for data exchange.
Prerequisites and Notes
JSContact is a data model for address books and directory services, and full element support is typically expected in protocols such as CardDAV and JMAP for Contacts. However, some protocols and document specifications may not require all semantics.
To address these situations, RFC 10050 defines an IANA registry for registering named subsets (profiles) of JSContact elements.
Basic Concepts of JSContact Profiles
A profile is a versioned, named set of JSContact elements (properties, types, values, etc.). Elements used within a profile must be registered in the IANA JSContact registry group.
A profile can define additional restrictions on the original definitions, but loosening restrictions is not permitted. A JSContact object is considered compliant with a profile if all of its properties are included in the set defined by the profile and their values conform to the restrictions.
flowchart TD
A[JSContact Object] --> B{Comply with Profile?}
B -- Yes --> C[Properties in Profile Set]
B -- Yes --> D[Values Meet Restrictions]
C --> E[Valid Data Exchange]
D --> E
B -- No --> F[Protocol-Specific Handling]
Profile Name and Version Specifications
Profiles are assigned a unique name and version.
Profile Name: Consists of ASCII lowercase letters and digits, and may be separated by hyphens. It must start with a letter and be between 1 and 255 characters in length.
Profile Version: A positive integer that must be incremented whenever the profile properties change. The initial value is 1.
Components of Property Entries
A profile defines a list of property entries that determine the supported properties. Each entry includes the following elements.
Property Name: The referenced JSContact property name.
Property Context: A comma-separated list of JSContact object types that support this profile.
Restricted Attributes: Restricts property attributes. For example, specifying "mandatory" makes a property mandatory even if it is normally optional.
Restricted Property Type: Restricts the property value type to prevent future type expansions or limit it to a subset of the original type.
Restricted Enum Values: Restricts enumeration values to a subset of allowed values.
Restricted PatchObject: Restricts PatchObject keys to a single JSON Pointer reference token (when the value is "yes").
Note that in all profiles, the @type and version properties are always supported and therefore cannot be included in profile entries.
Process for Determining Supported Properties
The supported properties of a profile are determined based on profile entries and IANA-registered properties. The steps are outlined below.
If there is an entry with "Card" in the property context, initialize the set with that property. If no such entry exists, initialize with all IANA-registered properties of the Card object.
If a property in the set has an object type, list, map, or a union of object types, add properties that include those object types in their context. If none exist, add IANA-registered properties.
Repeat the above steps until all object types have been considered.
IANA Considerations
This specification establishes a new "JSContact Profiles" registry with IANA. The addition of new profile names or versions follows the "Specification Required" policy, and updates to existing profiles follow "Expert Review." Registered entries include the name, version, and a reference to the specification.
Summary
The pre-execution check points and constraints covered in this article are as follows.
[Before verification on real devices] Actual communication logs and interactions with the JMAP/CardDAV server have not been performed.
You must verify that the profile name complies with the naming convention (lowercase letters, numbers, hyphens, 1 to 255 characters).
It is important to validate during the design phase whether property restrictions (such as mandatory fields and type constraints) contradict the original definitions.
