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.\" Copyright (c) 2019 Ted Unangst
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.Dd $Mdocdate$
.Dt ACTIVITYPUB 7
.Os
.Sh NAME
.Nm activitypub
.Nd notes about the honk implementation
.Sh DESCRIPTION
The
.Xr honk 1
utility processes status updates and other microblog activities using the
.Nm ActivityPub
protocol to exchange messages with other servers.
The specification is subject to interpretation, and not all implementations
behave in the same way.
This document attempts to clarify honk's behavior.
It is not intended to be a complete description of
.Nm ActivityPub ,
but may be useful as a guide to other implementors looking to interoperate.
.Ss OBJECTS
The following object or document types are supported.
.Bl -tag -width tenletters
.It Vt Note
Fully supported.
The default object type for honk.
.It Vt Article
Fully supported.
.It Vt Page
Supported.
.It Vt Question
Read only support.
Appears similar to a Note.
.It Vt Event
Supported.
Appears similar to a Note.
Can be both created and received, but
.Vt Invite
activities are ignored.
.It Vt Video
Limited support.
.It Vt Audio
Limited Support.
.El
.Pp
Honk primarily supports HTML content, not markdown or other formats,
with a wide range of permitted HTML tags in object
.Fa content
fields.
The following tags are supported.
.Bd -literal -offset indent
a, img, span,
div, h1, h2, h3, h4, h5, h6, hr,
table, thead, tbody, tfoot, th, tr, td, colgroup, col,
p, br, pre, code, blockquote, q,
caption, kbd, time, wbr, aside,
ruby, rtc, rb, rt, details, summary,
samp, mark, ins, dfn, cite, abbr, address,
strong, em, b, i, s, u, sub, sup, del, tt, small,
ol, ul, li, dl, dt, dd
.Ed
.Pp
The following tag attributes are permitted.
.Bd -literal -offset indent
href, src, alt, colspan, rowspan
.Ed
.Pp
The following class names are used for syntax highlighting code blocks.
.Bd -literal -offset indent
kw, bi, st, nm, tp, op, cm, al, dl
.Ed
.Ss ACTIVITIES
The following activities are supported.
.Bl -tag -width tenletters
.It Vt Create
Fully supported.
.It Vt Announce
Supported with share semantics.
.It Vt Read
Supported.
Primarily used to acknowledge replies and complete threads.
Can be interpreted to mean reply is approved, if not endorsed.
.It Vt Add
Works with collections.
.It Vt Follow
Supported.
Can follow both actors and collections.
.Vt Accept
and
.Vt Undo
require that the original request be quoted, not referred to by URI.
.It Vt Update
Supported.
Honk sends and receives
.Vt Update
activities.
.It Vt Delete
Does what it can.
.It Vt Like
Don't be ridiculous.
.It Vt ReactionEmoji
Kinda sorta.
.El
.Ss METADATA
The following additional object types are supported, typically as
.Fa tag
or
.Fa attachment .
.Bl -tag -width tenletters
.It Mention
Pretty @ machine.
.It Emoji
Inline text :emoji: with image replacement.
.It Place
Included as a
.Fa location .
Supports
.Fa name ,
.Fa url ,
.Fa latitude ,
and
.Fa longitude .
.It Document
Plain text and images in jpeg, gif, png, and webp formats are supported.
Other formats are linked to origin.
.El
.Pp
The
.Fa replies
array will be populated with a list of acknowledged replies.
.Ss EXTENSIONS
Honk also supports a
.Vt Ping
activity and will respond with a
.Vt Pong
activity.
This is useful for debugging networking connectivity issues without
visible side effects.
See ping.txt for details.
.Ss SECURITY
Honk uses http signatures.
.Ss WEBFINGER
Honk implements the
.Vt webfinger
end point and will use it for @mention resolution.
It is not required for federation.
.Ss LD-JSON
Not really.
.Sh SEE ALSO
.Xr intro 1 ,
.Xr honk 1
.Sh STANDARDS
.Pp
.Lk https://www.w3.org/TR/activitypub/ "ActivityPub"
.Pp
.Lk https://www.w3.org/TR/activitystreams-vocabulary/ "Activity Vocabulary"
.Sh CAVEATS
The ActivityPub standard is subject to interpretation, and not all
implementations are as enlightened as honk.