Protocol version

ANP 1.1 is the default latest version. ANP 1.0 remains available as an archive.

ANP Profile 4: Group Messaging Base Semantics

Document ID: ANP-P4
Title: Group Messaging Base Semantics
Status: Released
Version: 1.1
Language: English
Applicability: This Profile applies to the group life cycle, group management and group message base semantics based on Group DID, and does not include the group end-to-end encryption algorithm itself.

Note: This release converges the v1 core into two paths: "self-service joining and direct addition":
group.invite, group.accept_invite and standard invitation objects have been moved out of the v1 core;
membership_request, membership_request_digest, group.approve_membership, and group.reject_membership have been moved out of the v1 core;
group_policy converges to message_security_profile + bootstrap_security_profile + admission_mode + permissions;
Non-member governance directed notification group.governance_notice has been moved out of v1 core;
Reserve group.state_changed as the order status notification within the group.

1. Purpose

This Profile defines the group base semantics layer of ANP, stipulating:

Group DID serves as the application layer global identifier of the group;
Basic actions such as group creation, self-service joining, direct member addition, member removal, leaving the group, updating group information, and updating group policies;
base semantics of group message group.send;
ordering responsibilities of Group Host Service;
How Group E2EE Overlay is superimposed on the application semantics of this Profile.

This Profile does not define:

Specific group E2EE algorithm;
Pull historical messages;
Read and online status;
Device or internal copy concept;
Group external directory synchronization details;
Deploy a specific delivery mechanism for private invitation links, Join Token or other out-of-band group membership credentials;
How dynamic group state is stored inside the Agent.

2. Terminology and Normative Conventions

2.1 Normative Keywords

In this article, MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, SHOULD NOT, RECOMMENDED, NOT RECOMMENDED, MAY, OPTIONAL are interpreted as normative requirements according to their capitalized form.

2.2 Terminology

Group: Group protocol subject identified by group_did.
Group Host Service: The service responsible for the basic status ordering, policy application and group message entry of the group.
Group State: The application layer state of a group at a certain moment, including information, policies, membership relationships, etc.
Group State Version: The current group state version identifier assigned by the Group Host Service.
Group Event Sequence: The group event monotonically increasing sequence number assigned by the Group Host Service covers control operations and group messages.
Member: Agent member in the group.
Admission Mode: The group’s admission path is open to non-members by default. The standard values of this Profile v1 are admin-add and open-join. Among them, the Chinese "automatic join" online protocol value is uniformly written as open-join.
Policy: Application-layer rules that determine who may send messages, add members directly, remove members, update group information, and update policies.
Origin Proof: Application layer origin proof generated by the Agent that initiates group operations or group messages based on did:wba JSON bearer authentication.
Group Receipt: A verifiable receipt object generated by the Group Host and used to prove that a group operation or group message has been accepted by the group and obtained a certain status.
Logical Target URI: To make application layer signatures stable across forwards, a logical target URI defined globally by P1 Appendix A, rather than a specific HTTP URL for a hop.
Group State Changed Event: Group state change event object synchronized by Group Host ordering to the currently active members.

3. Design Principles

3.1 A group, a Group DID

Each group MUST have one group_did. group_did is the application layer global identifier of this group and is used for:

Group discovery;
Group management;
Group message addressing;
Binding anchor point for subsequent Group E2EE Overlay.

3.2 Group Host is responsible for ordering

All operations that change group state MUST be accepted and ordered by the Group Host Service.

The Group Host Service MUST maintain a well-defined linear ordering of group-state changes and assign a new group_state_version to each accepted state change.

3.3 Separation of application semantics and cryptographic semantics

This Profile only defines the application layer actions and objects of the group; specific group key establishment, member encryption status evolution, welcome messages, encrypted application messages and other capabilities are defined by the Group E2EE Profile.

3.4 The end point of the protocol is still Agent

Group members are still agents at the protocol layer. Any replicas, workers, devices, or terminals that exist within the Agent do not enter the interoperability semantics of this Profile.

3.5 Non-Goals

This Profile does not provide:

Global history playback;
Strong synchronization semantics;
Device-level membership;
Device-level delivery;
Internal executor-level permission control;
Standardized approval flow.

3.6 Separation of Initiator Authentication and Group Result Witnessing

There are usually two signatures with different semantics in group scenarios:

Initiator's signature: Proves that a certain sender_did actually initiated the group operation or group message;
group result witnessing: Proves that an operation or message has been accepted by the group and assigned a confirmed group_state_version, group_event_seq, or equivalent state position.

This Profile requires:

All requests that will change the group state, and group.send, MUST carry the initiator's auth.origin_proof;
The Group DID signature SHOULD appear in the group_receipt returned by the Group Host;
Recipients MUST NOT replace the initiator's signature with the group signature, and MUST NOT replace group-result witnessing with the initiator's signature.

3.7 Group entry path convergence

In the v1 core, only two standard actions are reserved for non-members joining the group:

group.join: The target Agent initiates joining independently and immediately becomes a member of active upon success;
group.add: Existing authorized members directly add the target Agent to the group, and it will take effect immediately upon success.

This Profile v1 does not define the standard invitation object, invitation_id, group.invite, or group.accept_invite. If the deployment requires an invitation link, Join Token, or other out-of-band credentials to assist group.join, these capabilities MUST be handled as deployment extensions, and MUST NOT create standard member status before group.join succeeds.

This Profile v1 does not define a standardized approval flow, nor does it introduce the pending intermediate governance state into the core.

4. Overview of group governance model (non-normative)

4.1 Summary list of rules

Scenario	Entry Method	Immediate Result	Authoritative Object/State	When Becomes `active`	Remarks
Self-service joining	`group.join`	The caller joins the group	`group_member.status = active`	This join will take effect immediately	Only applicable to `open-join`
Add a member directly	`group.add`	The target is added directly	`group_member.status = active`	Effective immediately for this addition	Typically used for `admin-add`
Members actively leave the group	`group.leave`	Members withdraw from the group	`group_member.status = left`	Not applicable	Only for current `active` members
Administrator removes member	`group.remove`	Member removed from group	`group_member.status = removed`	Not applicable	Applies only to current `active` members

Note: If the deployer guides joining through the out-of-band invitation link, Join Token or on-site reminder, the standard interoperability layer will still MUST show a successful result of group.join or group.add in the end.

4.2 Status object comparison table

Object	Key Status	Meaning
`group_member`	`active`	Application layer membership is in effect
`group_member`	`left` / `removed`	Membership ended

4.3 State Machine Diagram

mermaid

stateDiagram-v2
    [*] --> NonMember

    NonMember --> Active: group.join (open-join)
    NonMember --> Active: group.add

    Active --> Left: group.leave
    Active --> Removed: group.remove

5. Profile identification and dependencies

5.1 Profile name

The standard name of this Profile is:

anp.group.base.v1

5.2 Dependencies

This Profile MUST depend on the following Profiles:

anp.core.binding.v1
anp.identity.discovery.v1

5.3 Security Profile

When this Profile is used as an independently running basic group profile:

meta.profile MUST equal anp.group.base.v1
meta.security_profile MUST equal transport-protected

If the Group E2EE Overlay is subsequently superimposed, the corresponding security profile MUST specify how to cryptographically bind the group state object and group message object of this profile.

6. Group model

6.1 `group_did`

group_did is the application layer global identifier of the group.

group_did:

MUST be used as the target identifier for group-management operations;
MUST serve as the target identifier for group-message operations;
MUST NOT be treated as automatically equivalent to the internal group_id of any particular cryptographic implementation.

6.2 `group_state_version`

group_state_version identifies the current version of the application-layer group state.

The requirements are as follows:

MUST be assigned by the Group Host Service;
MUST be treated as an opaque string;
Each successful group-state change MUST generate a new group_state_version;
Sending a group message MUST NOT advance group_state_version;
The group_state_version returned in the successful response to a group message identifies the group-state snapshot to which that message was accepted.

6.3 `group_event_seq`

group_event_seq represents the group event sequence number.

The requirements are as follows:

MUST monotonically increases within the same group;
MUST cover group control operations and group messages;
MUST be represented by a decimal string;
MUST NOT directly serves as the only basis for security semantics.

The point most easily confused in P4 is which actions advance the group-state version, which actions only advance the group event sequence, and what exactly group_receipt anchors. The following diagram puts these three relationships into one view.

mermaid

flowchart TD
COps[Group state-changing operations<br/>create / join / add / remove / leave / update_*]
Msg[group.send]

COps --> SV[Advance group_state_version]
COps --> SEQ[Advance group_event_seq]

Msg --> SEQ
Msg --> SNAP[Reference current group_state_version snapshot]

SV --> RC[group_receipt]
SEQ --> RC
SNAP --> RC

RC --> OUT[Anchored result in response / notification]

Figure P4-1: Relationship among group_state_version, group_event_seq, and group_receipt (non-normative).

When reading the subsequent semantics of group.send, group.state_changed, and group_receipt, always return to this diagram: group messages participate in event ordering, but a message itself does not advance a new group_state_version.

6.4 Role model

This Profile minimum interoperability MUST support the following roles:

owner
admin
member

The role hierarchy is fixed at:

owner > admin > member

The interpretation rules are as follows:

When an action requires the minimum character to be member, admin and owner are automatically satisfied;
When an action requires the minimum character to be admin, owner is automatically satisfied;
v1 MUST NOT introduce custom roles within the minimum interoperability scope.

6.5 Member status

This Profile minimum interoperability MUST support the following member states:

active
left
removed

7. Standard objects

7.1 `group_policy`

group_policy represents the application layer authorization and group entry rule objects of the group.

The recommended structure is as follows:

json

{
  "message_security_profile": "transport-protected",
  "bootstrap_security_profile": "transport-protected",
  "admission_mode": "open-join",
  "permissions": {
    "send": "member",
    "add": "admin",
    "remove": "admin",
    "update_profile": "admin",
    "update_policy": "owner"
  },
  "attachments_allowed": true,
  "max_members": "500"
}

Field description:

message_security_profile: string, SHOULD, recommended values: transport-protected, group-e2ee
bootstrap_security_profile: string, SHOULD, recommended values: transport-protected, group-e2ee
admission_mode: string, MUST
permissions: Object, MUST
attachments_allowed: Boolean value, MAY
max_members: decimal string, MAY

The interpretation rules are as follows:

message_security_profile constraints:
- group.send
- Member-only group operations after becoming a member of active
bootstrap_security_profile constraints:
- group.join
- and subsequent Overlay's clearly defined onboarding / bootstrap methods
admission_mode MUST take one of the following values:
- admin-add
- open-join
permissions MUST contain and only contains the following standard keys:
- send
- add
- remove
- update_profile
- update_policy
The value MUST of permissions.* is:
- owner
- admin
- member
The default interpretation rules are as follows:
- When admission_mode = "admin-add", group.join MUST be rejected; the typical entry path is group.add
- group.join MUST be allowed when admission_mode = "open-join"
- Whether group.add is available is still determined by permissions.add
If max_members exists, Group Host MUST interpret it as the active member limit.

7.2 `group_member`

group_member represents the group membership object.

Minimum recommended fields:

agent_did: string, MUST
role: string, MUST
status: string, MUST
joined_at: RFC 3339 time string, MAY
added_by: DID string, MAY

Notes:

By default, the receiver MUST interpret role as member;
status = active indicates that the application layer membership has taken effect;
status = left or removed indicates that the membership has been terminated;
added_by is only recommended if the current membership was established by group.add.

7.3 Deploy extended group credentials

This Profile v1 does not define the standard invitation object, nor does it define invitation_id.

If the deployment requires an invitation link, Join Token, or other out-of-band credentials to assist group.join, these objects MAY exist, but they:

MUST NOT be considered a v1 core interworking object;
MUST NOT create a standard member state before group.join succeeds;
SHOULD be distributed through controlled channels.

7.4 `group_profile`

group_profile represents the group's presentational data object.

Recommended fields:

display_name: string, provided by SHOULD when creating a group
description: string, MAY
avatar_uri: string, MAY
discoverability: string, MAY, recommended values: private, listed, public
labels: Object, MAY

7.5 `group_state_ref`

group_state_ref represents the group state reference object.

Minimum recommended fields:

group_did: string, MUST
group_state_version: string, MUST
policy_hash: string, MAY
roster_hash: string, MAY

7.6 Group message payload

meta.content_type MUST for group.send exists.

This Profile minimum interoperability MUST support the following content types:

text/plain
application/json
application/anp-attachment-manifest+json

Among group.send and body, among text, payload and payload_b64u:

Exactly one of these fields MUST be present;
If more than one appears, the recipient MUST reject the request;
If none of the three are present, the receiving party MUST reject the request.

For payload_b64u:

MUST use no padding base64url;
SHOULD be used only for binary extensions or private extension objects.

When meta.content_type = "application/json", body.payload MUST carry
the JSON object directly. This Profile does not define the business meaning of
fields inside that object; group applications or hosts decide how to interpret it.

7.7 `auth` object

All requests that change the group state, except group.get_info, and group.send, whose params MUST contain an auth object.

The proof bearer rules, Signed Request Object and signature component mapping in this section MUST reuse the unified definition in P1 Appendix A; P4 no longer defines independent proof field names, independent Signed Payload structures or local @target-uri mappings.

The recommended structure is as follows:

json

{
  "auth": {
    "scheme": "anp-rfc9421-origin-proof-v1",
    "origin_proof": {
      "contentDigest": "sha-256=:BASE64_SHA256_DIGEST:",
      "signatureInput": "sig1=(\"@method\" \"@target-uri\" \"content-digest\");created=1733402096;expires=1733402156;nonce=\"abc123\";keyid=\"did:wba:example.com:user:alice:e1_<fingerprint>#key-1\"",
      "signature": "sig1=:BASE64_SIGNATURE:"
    }
  }
}

Field requirements:

auth.scheme MUST equal anp-rfc9421-origin-proof-v1
auth.origin_proof MUST exist in all state-changing group operations and group.send
auth itself MUST NOT enter contentDigest

7.8 Binding to the Shared Signed Request Object

auth.origin_proof.contentDigest MUST bind the shared Signed Request Object defined in P1 Appendix A.

For Group Base:

For message class methods such as group.send, meta.message_id and meta.content_type MUST exist
For group.create, meta.target.kind MUST be service
For other group operations targeting existing groups, meta.target.kind MUST be group

7.8.1 Reference to the Global Component Mapping

All Group Base methods requiring auth.origin_proof MUST use the global signature component map defined in P1 Appendix A.

Therefore:

For group.create, the verifier reconstructs @target-uri = anp://service/<pct-encoded meta.target.did> based on meta.target.kind = "service"
For group operations targeting an existing group, the verifier rebuilds @target-uri = anp://group/<pct-encoded meta.target.did> based on meta.target.kind = "group"
The above results come from the global rules of P1, and are not a set of local mappings independently defined by P4

7.9 `group_receipt`

group_receipt indicates that a group operation or group message has been accepted by the Group Host and written to the verifiable witness object of the group state machine.

Recommended fields:

receipt_type: string, MUST, recommended values: group-operation-accepted, group-message-accepted
group_did: string, MUST
group_state_version: string, MUST
group_event_seq: decimal string, MUST
subject_method: string, MUST
operation_id: string, MUST
message_id: string, MAY
actor_did: string, MUST
accepted_at: RFC 3339 time string, MUST
payload_digest: string, MUST
proof: object, SHOULD; when group_receipt will leave the domain where the Group Host is located and be dependent on other domains MUST

group_receipt.proof MUST reuse the shared Object Proof Profile defined in P1 Appendix B.

For group_receipt:

issuer DID MUST be group_did
The protected document MUST be the entire group_receipt after removing proof
proof.verificationMethod MUST point to the authentication method authorized by assertionMethod in the group_did DID document
The signature Purpose of group_receipt is to prove "the group has accepted this result", rather than to prove "who initiated the request"

In addition to the sharing rules of P1 Appendix B, group_receipt still MUST contain at least the following security-critical fields, and are therefore protected in their entirety by proof:

receipt_type
group_did
group_state_version
group_event_seq
subject_method
operation_id
actor_did
accepted_at
payload_digest
message_id, if present, is also MUST included and protected

After group_receipt.proof has been verified successfully, the verifier MUST continue to check that the above fields are consistent with the actual response, the notification context, and the corresponding group-state position.

7.10 Group State Change Event Object

This section converges the state change events used by group.state_changed into a unified event object, and distinguishes specific events through event_type.

7.10.1 Common fields

The recommended structure of the unified event object is as follows:

json

{
  "event_id": "evt-001",
  "event_type": "member-activated",
  "group_did": "did:example:group-123",
  "group_state_version": "43",
  "group_event_seq": "129",
  "subject_method": "group.join",
  "changed_at": "2026-03-29T14:11:00Z",
  "actor_did": "did:example:agent-b",
  "subject_did": "did:example:agent-c",
  "membership_status": "active",
  "group_profile": { "...": "..." },
  "group_policy": { "...": "..." },
  "group_receipt": { "...": "..." }
}

The common rules are as follows:

body MUST of group.state_changed directly carries an event object;
It MUST NOT be used to send out-of-band group entry credentials, reminders or result notifications to objects that have not yet become group members;
It SHOULD maintain the same sequential semantics as group_event_seq;
If subject_method = "group.join" or "group.add", then event_type = "member-activated".

7.10.2 Standard `event_type`

This Profile v1 recommends the following event_type:

member-activated
member-removed
member-left
group-profile-updated
group-policy-updated

Among them:

member-activated MUST contain subject_did and membership_status = "active"
member-removed MUST contain subject_did
member-left MUST contain subject_did
group-profile-updated SHOULD contain group_profile
group-policy-updated SHOULD contain group_policy

8. Standard methods and notifications

Except for group.get_info, requests for all state-changing methods in this section MUST meet the following general rules:

params.auth.scheme MUST equal anp-rfc9421-origin-proof-v1
params.auth.origin_proof MUST exist and binds the corresponding Signed Request Object
If the request crosses a domain boundary, the original auth.origin_proof MUST be forwarded with the message and MUST NOT be overwritten by the intermediate service

For all state-changing methods accepted by the Group Host, as well as group.send:

In a non-federated deployment, the successful response SHOULD return group_receipt
If the response leaves the Group Host's domain and is intended to be relied upon by another domain, the successful response MUST return group_receipt, and group_receipt.proof MUST be present

The following two Notification / asynchronous message methods:

group.incoming
group.state_changed

Belongs to OPTIONAL push capability. They are not required minimum interoperability methods for this Profile; but once implemented, the sender MUST use the standard Notification envelope and standard body structure defined by this Profile.

8.1 `group.create`

8.1.1 Semantics

Create a new group and assign a new group_did and initial group_state_version by the Group Host Service.

8.1.2 Request Requirements

group.create request MUST satisfy:

method = "group.create"
meta.profile = "anp.group.base.v1"
meta.security_profile = "transport-protected"
meta.sender_did MUST exist
meta.target.kind = "service"
meta.target.did MUST equal target ANPMessageService.serviceDid
meta.operation_id MUST exist
body.group_profile SHOULD exist
body.group_policy MUST exist
body.initial_members MAY exist
params.auth.origin_proof MUST exist

Regarding body.initial_members, Group Host MUST be processed according to the following rules:

The creator himself MUST become owner and immediately active;
If other initial_members exists, the Group Host MAY interpret it as the equivalent group.add during the creation phase;
Entries in initial_members that do not explicitly declare role MUST be interpreted as member.

8.1.3 Successful Response

A successful response MUST contain at least:

group_did
group_state_version
created_at
creator_did

A successful response MAY contain:

group_event_seq
group_profile
group_policy
group_receipt

8.2 `group.get_info`

8.2.1 Semantics

Get a snapshot of the current group's basic information.

8.2.2 Request Requirements

meta.target.kind MUST be "group"
meta.target.did MUST target group_did

body MAY contain:

include_policy
include_member_list

The identity requirements are as follows:

When the group's discoverability = "public" or "listed", group.get_info MAY be called as an anonymous read; at this time, meta.sender_did MAY be omitted;
When the group's discoverability = "private", the caller MUST provide an identity;
If the requested projection is outside the caller's visible range, the receiver MUST return group.policy_violation.

8.2.3 Successful Response

A successful response MUST contain at least:

group_did
group_state_version
group_profile

A successful response MAY contain:

group_policy (only if include_policy = true and the caller has permission to view)
member_list (only if include_member_list = true and the caller has permission to view; its element type MUST be group_member)
member_count (decimal string; if present, SHOULD represent the current number of active members)

If member_list is returned, its content SHOULD only contains the current active member.

8.3 `group.join`

8.3.1 Semantics

group.join is used for non-members to initiate joining independently. For v1 cores, the caller immediately becomes a member of active on success.

8.3.2 Request Requirements

body MAY contain:

reason_text

If the group is not currently in open-join mode, the recipient MUST reject the request and SHOULD return group.policy_violation.

8.3.3 Successful Response

A successful response MUST contain at least:

group_did
membership_status, and MUST be active
group_state_version

A successful response MAY contain:

group_receipt

8.4 `group.add`

8.4.1 Semantics

Members with permissions can directly add the target Agent to the group; upon success, the target will immediately become a member of active.

8.4.2 Request Requirements

body MUST contain:

member_did

body MAY contain:

role
reason_text

When role is not provided explicitly, the receiver MUST interpret member as such.

8.4.3 Successful Response

A successful response MUST contain at least:

group_did
member_did
membership_status, and MUST be active
group_state_version

A successful response MAY contain:

group_receipt

8.5 `group.remove`

8.5.1 Semantics

A current active member is removed from the group by an authorized member.

8.5.2 Request Requirements

body MUST contain:

member_did

body MAY contain:

reason_text

8.5.3 Processing rules

If the target is currently at active, then group.remove MUST make it group_member.status = "removed";
If the target is already left, removed, or does not exist, the recipient MUST reject the request.

8.5.4 Successful Response

A successful response MUST contain at least:

group_did
member_did
group_state_version

A successful response MAY contain:

membership_status
group_receipt

8.6 `group.leave`

8.6.1 Semantics

Indicates that the current sender actively exits the group.

8.6.2 Request Requirements

meta.sender_did MUST be the current leave-group member

8.6.3 Successful Response

A successful response MUST contain at least:

group_did
leaver_did
group_state_version

A successful response MAY contain:

group_receipt

8.7 `group.update_profile`

8.7.1 Semantics

Update the group display data object.

8.7.2 Request Requirements

body MUST contain:

group_profile_patch

group_profile_patch MUST use RFC 7386 JSON Merge Patch semantics.

8.7.3 Successful Response

A successful response MUST contain at least:

group_did
group_state_version
group_profile

A successful response MAY contain:

group_receipt

8.8 `group.update_policy`

8.8.1 Semantics

Update the group policy object.

8.8.2 Request Requirements

body MUST contain:

group_policy_patch

group_policy_patch MUST use RFC 7386 JSON Merge Patch semantics.

8.8.3 Successful Response

A successful response MUST contain at least:

group_did
group_state_version
group_policy

A successful response MAY contain:

group_receipt

8.9 `group.send`

8.9.1 Semantics

Send an application layer group message to a group.

8.9.2 Request Requirements

A compliant group.send request MUST satisfy:

method = "group.send"
meta.profile = "anp.group.base.v1"
meta.security_profile = "transport-protected"
meta.target.kind = "group"
meta.target.did MUST be the target group_did
meta.sender_did MUST be the current sender Agent DID
meta.message_id MUST exist
meta.operation_id MUST exist
meta.content_type MUST exist
body MUST satisfy the payload mutual exclusion rule
params.auth.origin_proof MUST exist and binds Signed Request Object

8.9.3 `body` of `group.send`

group.send of body can contain:

thread_id: string, MAY
reply_to_message_id: string, MAY
annotations: Object, MAY
Exactly one of text, payload, or payload_b64u MUST be present

8.9.4 Successful Response

A successful response MUST contain at least:

accepted = true
group_did
message_id
operation_id
group_event_seq
group_state_version
accepted_at

A successful response MAY contain:

group_receipt

8.10 `group.incoming`

group.incoming is used to asynchronously push a group message that has been accepted by the Group Host to the currently active member Agent. It MUST be used as a Notification.

If group.incoming is implemented, its Notification envelope MUST satisfy:

meta.profile = "anp.group.base.v1"
meta.security_profile MUST be equal to security profile when the group message is accepted
meta.target.kind = "agent"
meta.target.did MUST equal to the current notification recipient DID
meta.sender_did MUST equal to the service sender DID of the original group message
meta.operation_id MUST equal original group.send.meta.operation_id
meta.message_id MUST equal original group.send.meta.message_id
meta.content_type MUST equal meta.content_type of the original group message

The recommended structure of body is as follows:

json

{
  "group_did": "did:example:group-123",
  "group_state_version": "42",
  "group_event_seq": "128",
  "accepted_at": "2026-03-29T14:10:01Z",
  "group_receipt": { "...": "..." },
  "thread_id": "thr-001",
  "reply_to_message_id": "msg-0009",
  "annotations": {},
  "text": "hello group"
}

The rules are as follows:

body MUST carry the service payload consistent with the original group message;
If params.auth is present, then:
- params.auth.scheme MUST equal anp-rfc9421-origin-proof-v1
- params.auth.origin_proof MUST be a lossless copy of the original origin_proof
- Intermediate service MUST NOT rewrite new business proof.

8.11 `group.state_changed`

group.state_changed is the standard asynchronous notification method for group-state changes. It is used to synchronize ordered membership changes, group-data changes, and group-policy changes to currently active members. It MUST be used as a notification.

Its Notification envelope MUST satisfy:

meta.profile = "anp.group.base.v1"
meta.security_profile = "transport-protected"
meta.target.kind = "agent"
meta.target.did MUST equal to the current notification recipient DID
meta.sender_did MUST equal body.group_did
body MUST directly carry exactly one event object defined in Section 7.10

group.state_changed MUST NOT be used for out-of-band group-membership credential delivery, non-member reminders, or any targeted governance notification that would otherwise use direct.send.

9. Flow Overview (Non-Normative)

9.1 Self-service joining path (`open-join`)

mermaid

sequenceDiagram
    participant B as Applicant
    participant H as Group Host

    B->>H: group.join
    H-->>B: membership_status = active

9.2 Direct member-addition path (`admin-add`)

mermaid

sequenceDiagram
    participant A as Administrator
    participant H as Group Host
    participant B as Target Member

    A->>H: group.add
    H-->>A: member_did + membership_status = active
    H-->>B: group.state_changed / or deployment-specific custom notification

9.3 Group message path

mermaid

sequenceDiagram
    participant A as Sending Member
    participant H as Group Host
    participant M as Other Members

    A->>H: group.send
    H-->>A: accepted + group_event_seq
    H-->>M: group.incoming

10. ordering, Concurrency and Conflict

10.1 ordering Responsibilities

Group Host Service MUST maintain linear ordering for all accepted events for the same group_did. ordering covers:

group.create
group.join
group.add
group.remove
group.leave
group.update_profile
group.update_policy
group.send

10.2 Group message and status version

After group.send is accepted:

MUST allocate a new group_event_seq;
MUST NOT advance group_state_version because of the message itself;
The group_state_version returned with group_receipt represents the group-state snapshot to which the message was accepted.

10.3 Idempotence and deduplication

For group-state changes and group messages, the recipient MUST use the following fields as the idempotency basis:

sender_did
group_did
method
operation_id

The receiver MUST perform idempotency checks using that tuple.

For group.send, the receiver SHOULD additionally use the following fields for duplicate detection:

sender_did
group_did
message_id

The receiver SHOULD perform duplicate detection using that tuple.

11. Security and Policy

11.1 Secure transmission requirements

This Profile, when run independently, MUST rely on a certified secure transport layer.

11.2 Group operation initiator authentication

For all state-changing group operations and group.send:

The Group Host Service MUST authenticate auth.origin_proof;
The DID to which keyid of auth.origin_proof belongs MUST be consistent with meta.sender_did;
The authentication method pointed to by keyid MUST be authorized by the authentication relationship of the DID document;
For path type e1_ DID, Group Host Service MUST verify the relationship between the DID and the bound public key according to the did:wba specification;
The proof bearer rule MUST also satisfies the shared Origin Proof convention of P1 Appendix A.

11.3 The relationship between initiator authentication and group policy authorization

Permissions such as "who may add members, remove members, update group information, update policies, or send messages" MUST be determined by group_policy.

Specifically, the receiver MUST be based on:

group_policy.permissions.send
group_policy.permissions.add
group_policy.permissions.remove
group_policy.permissions.update_profile
group_policy.permissions.update_policy
group_policy.admission_mode

Determine whether the current request is authorized.

11.4 Where to use group DID signature

The signature of the group DID is not the second signature of the client's inbound request. Its correct use is:

Witness the results of accepted group state changes;
Witness the accepted group.send result;
Provide cross-domain callers with portable proof that the operation/message was indeed accepted by the group.

For group_receipt.proof, its proof syntax, protected documents and verification steps MUST reuse the shared Object Proof Profile in P1 Appendix B.

11.5 Cross-Domain forwarding

If group operations or group messages are forwarded via other services:

The original auth.origin_proof MUST remain unchanged and forwarded with the request;
The target Group Host MUST independently verify auth.origin_proof;
MUST additionally perform service-level authentication between service hops.

11.6 Access Token optimization

The access token process MAY based on did:wba is used to optimize repeated calls between the caller and the Group Host, or between services, but:

An access token MUST NOT replace auth.origin_proof;
sender-constrained access token SHOULD take precedence over ordinary Bearer tokens.

11.7 security profile requirements

If message_security_profile in the group policy requires group-e2ee:

For member-only group operations on group.send and after becoming a member of active, the sender MUST use Group E2EE Profile;
Group Host Service MUST reject requests related to transport-protected.

If bootstrap_security_profile in the group policy requires group-e2ee:

For group.join and subsequent Overlay's clearly defined onboarding / bootstrap methods, the sender MUST use Group E2EE Profile;
Group Host Service MUST NOT silently downgrade to transport-protected without explicit negotiation.

11.8 Binding points with Overlay

Subsequent Group E2EE Overlay SHOULD bind at least the following fields:

group_did
sender_did
group_state_version or equivalent status reference
message_id
content_type
security_profile
auth.origin_proof.contentDigest or equivalent origin proof digest

12. Profile specific errors (recommended)

On the premise of following the ANP Core public error model, this Profile recommends the following anp_code:

`code`	`anp_code`	Meaning
3000	`group.not_member`	The caller is not a member of the group
3001	`group.already_member`	The target is already a group member
3002	`group.admission_not_allowed`	The current path to join the group is unavailable, or the prerequisites for joining the group are not met
3003	`group.policy_violation`	Operation violates group policy
3005	`group.member_conflict`	Member status conflict
3006	`group.security_mode_required`	The group has higher requirements security profile
3007	`group.host_unavailable`	Group Host is temporarily unavailable
3008	`group.invalid_origin_proof`	Initiator origin proof is invalid, expired or missing
3009	`group.origin_did_mismatch`	The DIDs to which `meta.sender_did` and `keyid` belong are inconsistent
3010	`group.invalid_group_receipt`	The group receipt signature is invalid or does not match the returned result

13. Privacy Considerations

13.1 Minimum Disclosure of Member List

Even if an implementation supports include_member_list, the Group Host SHOULD only returns the minimum necessary membership information to the authorized caller. For public groups, anonymous reads SHOULD NOT expose the full member list by default.

13.2 Propagation of out-of-band group entry credentials

If the deployer uses private invitation links, Join Tokens, or other out-of-band credentials to trigger group.join, the implementer SHOULD avoid exposing these actionable credentials to unrelated parties and SHOULD preferentially delivers them through controlled channels, out-of-band channels, or protected direct messagings.

13.3 Public discovery and anonymous reading

When the group is set to public or listed, an anonymous read SHOULD return only a minimal data snapshot; the caller SHOULD NOT infer internal membership, role distribution, or any other unnecessary state from such reads.

14. Minimum Interoperability Requirements

An implementation conforming to this Profile MUST support at least:

group.create
group.get_info
group.join
group.add
group.remove
group.leave
group.update_profile
group.update_policy
group.send
group_did
group_state_version
group_event_seq
Role: owner, admin, member
Member status: active, left, removed
Unified event object semantics of group.state_changed
Safe transmission operation mode

If an implementation provides a push capability, its group.incoming and group.state_changed MUST follow the standard Notification semantics of this Profile.

15. Example

15.1 `group.create` Example

json

{
  "jsonrpc": "2.0",
  "id": "req-30001",
  "method": "group.create",
  "params": {
    "meta": {
      "profile": "anp.group.base.v1",
      "security_profile": "transport-protected",
      "sender_did": "did:wba:a.example:agents:alice:e1_<fingerprint>",
      "target": {
        "kind": "service",
        "did": "did:wba:groups.example"
      },
      "operation_id": "op-30001",
      "created_at": "2026-03-29T12:30:00Z"
    },
    "auth": {
      "scheme": "anp-rfc9421-origin-proof-v1",
      "origin_proof": {
        "contentDigest": "sha-256=:BASE64_SHA256_OF_SIGNED_REQUEST_OBJECT:",
        "signatureInput": "sig1=(\"@method\" \"@target-uri\" \"content-digest\");created=1774787400;expires=1774787460;nonce=\"n-30001\";keyid=\"did:wba:a.example:agents:alice:e1_<fingerprint>#key-1\"",
        "signature": "sig1=:BASE64_SIGNATURE:"
      }
    },
    "body": {
      "group_profile": {
        "display_name": "Cross-Domain Agents",
        "description": "Collaboration Group",
        "discoverability": "private"
      },
      "group_policy": {
        "message_security_profile": "transport-protected",
        "bootstrap_security_profile": "transport-protected",
        "admission_mode": "admin-add",
        "permissions": {
          "send": "member",
          "add": "admin",
          "remove": "admin",
          "update_profile": "admin",
          "update_policy": "owner"
        },
        "attachments_allowed": true,
        "max_members": "500"
      },
      "initial_members": [
        {
          "agent_did": "did:wba:a.example:agents:alice:e1_<fingerprint>",
          "role": "owner"
        }
      ]
    }
  }
}

Ordinary JSON payload example:

json

{
  "jsonrpc": "2.0",
  "id": "req-30005",
  "method": "group.send",
  "params": {
    "meta": {
      "profile": "anp.group.base.v1",
      "security_profile": "transport-protected",
      "sender_did": "did:wba:a.example:agents:alice:e1_<fingerprint>",
      "target": {
        "kind": "group",
        "did": "did:wba:groups.example:team:dev:e1_<fingerprint>"
      },
      "operation_id": "msg-30005",
      "message_id": "msg-30005",
      "created_at": "2026-03-29T12:51:00Z",
      "content_type": "application/json"
    },
    "body": {
      "thread_id": "thr-001",
      "payload": {
        "type": "example",
        "data": {
          "hello": "group"
        }
      }
    }
  }
}

The fields inside payload are application-defined and are not specified by ANP.

Successful Response example:

json

{
  "jsonrpc": "2.0",
  "id": "req-30001",
  "result": {
    "group_did": "did:wba:groups.example:team:dev:e1_<fingerprint>",
    "group_state_version": "1",
    "group_event_seq": "1",
    "created_at": "2026-03-29T12:30:01Z",
    "creator_did": "did:wba:a.example:agents:alice:e1_<fingerprint>",
    "group_receipt": {
      "receipt_type": "group-operation-accepted",
      "group_did": "did:wba:groups.example:team:dev:e1_<fingerprint>",
      "group_state_version": "1",
      "group_event_seq": "1",
      "subject_method": "group.create",
      "operation_id": "op-30001",
      "actor_did": "did:wba:a.example:agents:alice:e1_<fingerprint>",
      "accepted_at": "2026-03-29T12:30:01Z",
      "payload_digest": "sha-256=:BASE64_SHA256_OF_SIGNED_REQUEST_OBJECT:",
      "proof": {
        "type": "DataIntegrityProof",
        "cryptosuite": "eddsa-jcs-2022",
        "verificationMethod": "did:wba:groups.example:team:dev:e1_<fingerprint>#assert-1",
        "proofPurpose": "assertionMethod",
        "created": "2026-03-29T12:30:01Z",
        "proofValue": "zBASE58MULTIBASE_PROOF"
      }
    }
  }
}

15.2 `group.add` Example

json

{
  "jsonrpc": "2.0",
  "id": "req-30002",
  "method": "group.add",
  "params": {
    "meta": {
      "profile": "anp.group.base.v1",
      "security_profile": "transport-protected",
      "sender_did": "did:wba:a.example:agents:alice:e1_<fingerprint>",
      "target": {
        "kind": "group",
        "did": "did:wba:groups.example:team:dev:e1_<fingerprint>"
      },
      "operation_id": "op-30002",
      "created_at": "2026-03-29T12:40:00Z"
    },
    "auth": {
      "scheme": "anp-rfc9421-origin-proof-v1",
      "origin_proof": {
        "contentDigest": "sha-256=:BASE64_SHA256_OF_SIGNED_REQUEST_OBJECT:",
        "signatureInput": "sig1=(\"@method\" \"@target-uri\" \"content-digest\");created=1774788000;expires=1774788060;nonce=\"n-30002\";keyid=\"did:wba:a.example:agents:alice:e1_<fingerprint>#key-1\"",
        "signature": "sig1=:BASE64_SIGNATURE:"
      }
    },
    "body": {
      "member_did": "did:wba:b.example:agents:bob:e1_<fingerprint>",
      "role": "member",
      "reason_text": "Join the collaboration group"
    }
  }
}

Successful Response example:

json

{
  "jsonrpc": "2.0",
  "id": "req-30002",
  "result": {
    "group_did": "did:wba:groups.example:team:dev:e1_<fingerprint>",
    "member_did": "did:wba:b.example:agents:bob:e1_<fingerprint>",
    "group_state_version": "2",
    "membership_status": "active",
    "group_receipt": {
      "receipt_type": "group-operation-accepted",
      "group_did": "did:wba:groups.example:team:dev:e1_<fingerprint>",
      "group_state_version": "2",
      "group_event_seq": "2",
      "subject_method": "group.add",
      "operation_id": "op-30002",
      "actor_did": "did:wba:a.example:agents:alice:e1_<fingerprint>",
      "accepted_at": "2026-03-29T12:40:01Z",
      "payload_digest": "sha-256=:BASE64_SHA256_OF_SIGNED_REQUEST_OBJECT:",
      "proof": {
        "type": "DataIntegrityProof",
        "cryptosuite": "eddsa-jcs-2022",
        "verificationMethod": "did:wba:groups.example:team:dev:e1_<fingerprint>#assert-1",
        "proofPurpose": "assertionMethod",
        "created": "2026-03-29T12:40:01Z",
        "proofValue": "zBASE58MULTIBASE_PROOF"
      }
    }
  }
}

15.3 `group.join` example (open to join)

json

{
  "jsonrpc": "2.0",
  "id": "req-30003",
  "method": "group.join",
  "params": {
    "meta": {
      "profile": "anp.group.base.v1",
      "security_profile": "transport-protected",
      "sender_did": "did:wba:c.example:agents:carol:e1_<fingerprint>",
      "target": {
        "kind": "group",
        "did": "did:wba:groups.example:public:news:e1_<fingerprint>"
      },
      "operation_id": "op-30003",
      "created_at": "2026-03-29T12:45:00Z"
    },
    "auth": {
      "scheme": "anp-rfc9421-origin-proof-v1",
      "origin_proof": {
        "contentDigest": "sha-256=:BASE64_SHA256_OF_SIGNED_REQUEST_OBJECT:",
        "signatureInput": "sig1=(\"@method\" \"@target-uri\" \"content-digest\");created=1774788300;expires=1774788360;nonce=\"n-30003\";keyid=\"did:wba:c.example:agents:carol:e1_<fingerprint>#key-1\"",
        "signature": "sig1=:BASE64_SIGNATURE:"
      }
    },
    "body": {
      "reason_text": "Subscribe to the public group"
    }
  }
}

Successful Response example:

json

{
  "jsonrpc": "2.0",
  "id": "req-30003",
  "result": {
    "group_did": "did:wba:groups.example:public:news:e1_<fingerprint>",
    "membership_status": "active",
    "group_state_version": "8",
    "group_receipt": {
      "receipt_type": "group-operation-accepted",
      "group_did": "did:wba:groups.example:public:news:e1_<fingerprint>",
      "group_state_version": "8",
      "group_event_seq": "41",
      "subject_method": "group.join",
      "operation_id": "op-30003",
      "actor_did": "did:wba:c.example:agents:carol:e1_<fingerprint>",
      "accepted_at": "2026-03-29T12:45:01Z",
      "payload_digest": "sha-256=:BASE64_SHA256_OF_SIGNED_REQUEST_OBJECT:",
      "proof": {
        "type": "DataIntegrityProof",
        "cryptosuite": "eddsa-jcs-2022",
        "verificationMethod": "did:wba:groups.example:public:news:e1_<fingerprint>#assert-1",
        "proofPurpose": "assertionMethod",
        "created": "2026-03-29T12:45:01Z",
        "proofValue": "zBASE58MULTIBASE_PROOF"
      }
    }
  }
}

15.4 `group.send` Example

json

{
  "jsonrpc": "2.0",
  "id": "req-30004",
  "method": "group.send",
  "params": {
    "meta": {
      "profile": "anp.group.base.v1",
      "security_profile": "transport-protected",
      "sender_did": "did:wba:a.example:agents:alice:e1_<fingerprint>",
      "target": {
        "kind": "group",
        "did": "did:wba:groups.example:team:dev:e1_<fingerprint>"
      },
      "operation_id": "msg-30004",
      "message_id": "msg-30004",
      "created_at": "2026-03-29T12:50:00Z",
      "content_type": "text/plain"
    },
    "auth": {
      "scheme": "anp-rfc9421-origin-proof-v1",
      "origin_proof": {
        "contentDigest": "sha-256=:BASE64_SHA256_OF_SIGNED_REQUEST_OBJECT:",
        "signatureInput": "sig1=(\"@method\" \"@target-uri\" \"content-digest\");created=1774788600;expires=1774788660;nonce=\"n-30004\";keyid=\"did:wba:a.example:agents:alice:e1_<fingerprint>#key-1\"",
        "signature": "sig1=:BASE64_SIGNATURE:"
      }
    },
    "body": {
      "thread_id": "thr-001",
      "text": "Hello everyone"
    }
  }
}

Successful Response example:

json

{
  "jsonrpc": "2.0",
  "id": "req-30004",
  "result": {
    "accepted": true,
    "group_did": "did:wba:groups.example:team:dev:e1_<fingerprint>",
    "message_id": "msg-30004",
    "operation_id": "msg-30004",
    "group_event_seq": "9",
    "group_state_version": "2",
    "accepted_at": "2026-03-29T12:50:01Z",
    "group_receipt": {
      "receipt_type": "group-message-accepted",
      "group_did": "did:wba:groups.example:team:dev:e1_<fingerprint>",
      "group_state_version": "2",
      "group_event_seq": "9",
      "subject_method": "group.send",
      "operation_id": "msg-30004",
      "message_id": "msg-30004",
      "actor_did": "did:wba:a.example:agents:alice:e1_<fingerprint>",
      "accepted_at": "2026-03-29T12:50:01Z",
      "payload_digest": "sha-256=:BASE64_SHA256_OF_SIGNED_REQUEST_OBJECT:",
      "proof": {
        "type": "DataIntegrityProof",
        "cryptosuite": "eddsa-jcs-2022",
        "verificationMethod": "did:wba:groups.example:team:dev:e1_<fingerprint>#assert-1",
        "proofPurpose": "assertionMethod",
        "created": "2026-03-29T12:50:01Z",
        "proofValue": "zBASE58MULTIBASE_PROOF"
      }
    }
  }
}

16. Registry Placeholder

Subsequent versions of this standard SHOULD establish the following registry:

Group role registration form;
Group member status registration form;
group_policy.admission_mode registry;
group.state_changed.event_type registry;
Group error code registration table.

17. Reference Implementation Notes (Non-Normative)

Implementers should adopt the following principles when implementing this Profile:

The v1 core only maintains the group_member group entry result object and does not introduce standard invitation or standardized approval objects;
group_policy uses a fixed admission_mode + permissions structure, which is clearer and easier to implement than a large number of Boolean switches;
group.incoming is responsible for group message push, and group.state_changed is responsible for orderly status synchronization within the group;
Capabilities such as private invitation links, Join Token, and site reminders are deployment extensions, not v1 core interoperability requirements;
group.send does not participate in group state version concurrency control. The server only needs to verify "whether the sender is currently a member of active and has send permissions."

ANP Profile 4: Group Messaging Base Semantics ​

1. Purpose ​

2. Terminology and Normative Conventions ​

2.1 Normative Keywords ​

2.2 Terminology ​

3. Design Principles ​

3.1 A group, a Group DID ​

3.2 Group Host is responsible for ordering ​

3.3 Separation of application semantics and cryptographic semantics ​

3.4 The end point of the protocol is still Agent ​

3.5 Non-Goals ​

3.6 Separation of Initiator Authentication and Group Result Witnessing ​

3.7 Group entry path convergence ​

4. Overview of group governance model (non-normative) ​

4.1 Summary list of rules ​

4.2 Status object comparison table ​

4.3 State Machine Diagram ​

5. Profile identification and dependencies ​

5.1 Profile name ​

5.2 Dependencies ​

5.3 Security Profile ​

6. Group model ​

6.1 group_did ​

6.2 group_state_version ​

6.3 group_event_seq ​

6.4 Role model ​

6.5 Member status ​

7. Standard objects ​

7.1 group_policy ​

7.2 group_member ​

7.3 Deploy extended group credentials ​

7.4 group_profile ​

7.5 group_state_ref ​

7.6 Group message payload ​

7.7 auth object ​

7.8 Binding to the Shared Signed Request Object ​

7.8.1 Reference to the Global Component Mapping ​

7.9 group_receipt ​

7.10 Group State Change Event Object ​

7.10.1 Common fields ​

7.10.2 Standard event_type ​

8. Standard methods and notifications ​

8.1 group.create ​

8.1.1 Semantics ​

8.1.2 Request Requirements ​

8.1.3 Successful Response ​

8.2 group.get_info ​

8.2.1 Semantics ​

8.2.2 Request Requirements ​

8.2.3 Successful Response ​

8.3 group.join ​

8.3.1 Semantics ​

8.3.2 Request Requirements ​

8.3.3 Successful Response ​

8.4 group.add ​

8.4.1 Semantics ​

8.4.2 Request Requirements ​

8.4.3 Successful Response ​

8.5 group.remove ​

8.5.1 Semantics ​

8.5.2 Request Requirements ​

8.5.3 Processing rules ​

8.5.4 Successful Response ​

8.6 group.leave ​

8.6.1 Semantics ​

8.6.2 Request Requirements ​

8.6.3 Successful Response ​

8.7 group.update_profile ​

8.7.1 Semantics ​

8.7.2 Request Requirements ​

8.7.3 Successful Response ​

8.8 group.update_policy ​

8.8.1 Semantics ​

8.8.2 Request Requirements ​

8.8.3 Successful Response ​

8.9 group.send ​

8.9.1 Semantics ​

8.9.2 Request Requirements ​

8.9.3 body of group.send ​

8.9.4 Successful Response ​

ANP Profile 4: Group Messaging Base Semantics

1. Purpose

2. Terminology and Normative Conventions

2.1 Normative Keywords

2.2 Terminology

3. Design Principles

3.1 A group, a Group DID

3.2 Group Host is responsible for ordering

3.3 Separation of application semantics and cryptographic semantics

3.4 The end point of the protocol is still Agent

3.5 Non-Goals

3.6 Separation of Initiator Authentication and Group Result Witnessing

3.7 Group entry path convergence

4. Overview of group governance model (non-normative)

4.1 Summary list of rules

4.2 Status object comparison table

4.3 State Machine Diagram

5. Profile identification and dependencies

5.1 Profile name

5.2 Dependencies

5.3 Security Profile

6. Group model

6.1 `group_did`

6.2 `group_state_version`

6.3 `group_event_seq`

6.4 Role model

6.5 Member status

7. Standard objects

7.1 `group_policy`

7.2 `group_member`

7.3 Deploy extended group credentials

7.4 `group_profile`

7.5 `group_state_ref`

7.6 Group message payload

7.7 `auth` object

7.8 Binding to the Shared Signed Request Object

7.8.1 Reference to the Global Component Mapping

7.9 `group_receipt`

7.10 Group State Change Event Object

7.10.1 Common fields

7.10.2 Standard `event_type`

8. Standard methods and notifications

8.1 `group.create`

8.1.1 Semantics

8.1.2 Request Requirements

8.1.3 Successful Response

8.2 `group.get_info`

8.2.1 Semantics

8.2.2 Request Requirements

8.2.3 Successful Response

8.3 `group.join`

8.3.1 Semantics

8.3.2 Request Requirements

8.3.3 Successful Response

8.4 `group.add`

8.4.1 Semantics

8.4.2 Request Requirements

8.4.3 Successful Response

8.5 `group.remove`

8.5.1 Semantics

8.5.2 Request Requirements

8.5.3 Processing rules

8.5.4 Successful Response

8.6 `group.leave`

8.6.1 Semantics

8.6.2 Request Requirements

8.6.3 Successful Response

8.7 `group.update_profile`

8.7.1 Semantics

8.7.2 Request Requirements

8.7.3 Successful Response

8.8 `group.update_policy`

8.8.1 Semantics

8.8.2 Request Requirements

8.8.3 Successful Response

8.9 `group.send`

8.9.1 Semantics

8.9.2 Request Requirements

8.9.3 `body` of `group.send`

8.9.4 Successful Response