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Richard van der Hoff 8 years ago
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specification/intro.rst
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@ -150,13 +150,13 @@ Users
~~~~~
Each client is associated with a user account, which is identified in Matrix
using a unique identifier, or "MXID". This ID is namespaced to the homeserver
using a unique identifier, or "user ID". This ID is namespaced to the homeserver
which allocated the account and has the form::
@localpart:domain
See the `Identifier Grammar`_ section for full details of the structure of
an MXID.
user IDs.
Events
~~~~~~
@ -317,14 +317,14 @@ that are in the room that can be used to join via.
Identity
~~~~~~~~
Users in Matrix are identified via their matrix user ID (MXID). However,
Users in Matrix are identified via their Matrix user ID. However,
existing 3rd party ID namespaces can also be used in order to identify Matrix
users. A Matrix "Identity" describes both the user ID and any other existing IDs
from third party namespaces *linked* to their account.
Matrix users can *link* third-party IDs (3PIDs) such as email addresses, social
network accounts and phone numbers to their user ID. Linking 3PIDs creates a
mapping from a 3PID to a user ID. This mapping can then be used by Matrix
users in order to discover the MXIDs of their contacts.
users in order to discover the user IDs of their contacts.
In order to ensure that the mapping from 3PID to user ID is genuine, a globally
federated cluster of trusted "Identity Servers" (IS) are used to verify the 3PID
and persist and replicate the mappings.
@ -376,12 +376,14 @@ be reached by other homeservers. The complete grammar is::
where ``host`` is as defined by `RFC3986, section 3.2.2
<https://tools.ietf.org/html/rfc3986#section-3.2.2>`_.
.. NOTE::
Examples of valid server names are:
The RFC3986 specification of a "host", allows IPv4 literals (``1.2.3.4``), and
IPv6 literals (``[1234:5678::abcd]``), as well as registered domain
names. Similarly, all of these formats are valid in Matrix server names and
identifiers.
* ``matrix.org``
* ``matrix.org:8888``
* ``1.2.3.4`` (IPv4 literal)
* ``1.2.3.4:1234`` (IPv4 literal with explicit port)
* ``[1234:5678::abcd]`` (IPv6 literal)
* ``[1234:5678::abcd]:5678`` (IPv6 literal with explicit port)
Common Identifier Format
@ -393,112 +395,110 @@ the form::
&localpart:domain
where ``&`` represents a 'sigil' character; ``domain`` is the server name of
where ``&`` represents a 'sigil' character; ``domain`` is the `server name`_ of
the homeserver which allocated the identifier, and ``localpart`` is an
identifier allocated by that homeserver.
The sigil characters are as follows:
* ``@``: User ID (MXID)
* ``@``: User ID
* ``!``: Room ID
* ``$``: Event ID
* ``#``: Room alias
In some cases (such as Room IDs and Event IDs), the ``domain`` is present only
for namespacing, to avoid clashes of identifiers between different
homeservers. In other cases (User IDs and Room aliases), it defines the
authoritative homeserver for contacting the user or room in question.
The precise grammar defining the allowable format of an identifier depends on
the type of identifier.
User Identifiers
++++++++++++++++
Users within Matrix are uniquely identified by their MXID. The MXID is
namespaced to the homeserver which allocated the account and has the form::
Users within Matrix are uniquely identified by their Matrix user ID. The user
ID is namespaced to the homeserver which allocated the account and has the
form::
@localpart:domain
The ``localpart`` of an MXID is an opaque identifier for that user. It MUST NOT
be empty, and MUST contain only the characters ``a-z``, ``0-9``, ``.``, ``_``,
``=``, and ``-``.
The ``localpart`` of a user ID is an opaque identifier for that user. It MUST
NOT be empty, and MUST contain only the characters ``a-z``, ``0-9``, ``.``,
``_``, ``=``, and ``-``.
The ``domain`` of an MXID is the server name of the homeserver which allocated
the account.
The ``domain`` of a user ID is the `server name`_ of the homeserver which
allocated the account.
The length of an MXID, including the ``@`` sigil and the domain, MUST NOT
The length of a user ID, including the ``@`` sigil and the domain, MUST NOT
exceed 255 characters.
The complete grammar for a legal MXID is::
The complete grammar for a legal user ID is::
mxid = "@" mxid_localpart ":" server_name
mxid_localpart = 1*mxid_char
mxid_char = DIGIT
/ %x61-7A ; a-z
/ "-" / "." / "=" / "_"
user_id = "@" user_id_localpart ":" server_name
user_id_localpart = 1*user_id_char
user_id_char = DIGIT
/ %x61-7A ; a-z
/ "-" / "." / "=" / "_"
.. admonition:: Rationale
A number of factors were considered when defining the allowable characters
for an MXID.
for a user ID.
Firstly, we chose to exclude characters outside the basic US-ASCII character
set. MXIDs are primarily intended for use as an identifier at the protocol
set. User IDs are primarily intended for use as an identifier at the protocol
level, and their use as a human-readable handle is of secondary
benefit. Furthermore, they are useful as a last-resort differentiator between
users with similar display names. Allowing the full unicode character set
would make very difficult for a human to distinguish two similar MXIDs. The
would make very difficult for a human to distinguish two similar user IDs. The
limited character set used has the advantage that even a user unfamiliar with
the Latin alphabet should be able to distinguish similar MXIDs manually, if
the Latin alphabet should be able to distinguish similar user IDs manually, if
somewhat laboriously.
We chose to disallow upper-case characters because we do not consider it
valid to have two MXIDs which differ only in case: indeed it should be
valid to have two user IDs which differ only in case: indeed it should be
possible to reach ``@user:matrix.org`` as ``@USER:matrix.org``. However,
MXIDs are necessarily used in a number of situations which are inherently
user IDs are necessarily used in a number of situations which are inherently
case-sensitive (notably in the ``state_key`` of ``m.room.member``
events). Forbidding upper-case characters (and requiring homeservers to
downcase usernames when creating MXIDs for new users) is a relatively simple
downcase usernames when creating user IDs for new users) is a relatively simple
way to ensure that ``@USER:matrix.org`` cannot refer to a different user to
``@user:matrix.org``.
Finally, we decided to restrict the allowable punctuation to a very basic set
to ensure that the identifier can be used as-is in as wide a number of
situations as possible, without requiring escaping. For instance, allowing
"%" or "/" would make it harder to use an MXID in a URI. "*" is used as a
"%" or "/" would make it harder to use a user ID in a URI. "*" is used as a
wildcard in some APIs (notably the filter API), so it also cannot be a legal
MXID character.
user ID character.
The length restriction is derived from the limit on the length of the
``sender`` key on events; since the MXID appears in every event sent by the
user, it is limited to ensure that the MXID does not dominate over the actual
``sender`` key on events; since the user ID appears in every event sent by the
user, it is limited to ensure that the user ID does not dominate over the actual
content of the events.
Historical MXIDs
<<<<<<<<<<<<<<<<
Matrix user IDs are sometimes informally referred to as MXIDs.
Historical User IDs
<<<<<<<<<<<<<<<<<<<
Older versions of this specification were more tolerant of the characters
permitted in MXID localparts. There are currently active users whose MXIDs do
not conform to the permitted character set, and a number of rooms whose history
includes events with a ``sender`` which does not conform. In order to handle
these rooms successfully, clients and servers MUST accept MXIDs with localparts
from the expanded character set::
permitted in user ID localparts. There are currently active users whose user
IDs do not conform to the permitted character set, and a number of rooms whose
history includes events with a ``sender`` which does not conform. In order to
handle these rooms successfully, clients and servers MUST accept user IDs with
localparts from the expanded character set::
extended_mxid_char = %x21-7E
extended_user_id_char = %x21-7E
Mapping from other character sets
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
In certain circumstances it will be desirable to map from a wider character set
onto the limited character set allowed in an MXID localpart. Examples include a
homeserver creating an MXID for a new user based on their chosen login ID, or a
bridge mapping user ids from another protocol.
onto the limited character set allowed in a user ID localpart. Examples include
a homeserver creating a user ID for a new user based on their chosen login ID,
or a bridge mapping user ids from another protocol.
Implmentations are free to do this mapping however they choose. Since the MXID
is opaque except to the implementation which created it, the only requirement
is that the implemention can perform the mapping consistently. However, we
suggest the following algorithm:
Implmentations are free to do this mapping however they choose. Since the user
ID is opaque except to the implementation which created it, the only
requirement is that the implemention can perform the mapping
consistently. However, we suggest the following algorithm:
1. Encode character strings as UTF-8.
@ -528,16 +528,18 @@ A room has exactly one room ID. A room ID has the format::
!opaque_id:domain
An event thas exactly one event ID. An event ID has the format::
An event has exactly one event ID. An event ID has the format::
$opaque_id:domain
The ``domain`` of a room/event ID is the server name of the homeserver which created
the room/event. Note that the domain is used only for namespacing - there is no
The ``domain`` of a room/event ID is the `server name`_ of the homeserver which
created the room/event. The domain is used only for namespacing to avoid the
risk of clashes of identifiers between different homeservers. There is no
implication that the room or event in question is still available at the
corresponding homeserver.
Event IDs and Room IDs are case-sensitive. They are not mant to be human readable.
Event IDs and Room IDs are case-sensitive. They are not meant to be human
readable.
.. TODO-spec
What is the grammar for the opaque part? https://matrix.org/jira/browse/SPEC-389
@ -549,10 +551,12 @@ A room may have zero or more aliases. A room alias has the format::
#room_alias:domain
The ``domain`` of a room alias is the server of the homeserver which created
the alias. Other servers may contact this homeserver to look up the alias.
The ``domain`` of a room alias is the `server name`_ of the homeserver which
created the alias. Other servers may contact this homeserver to look up the
alias.
Room aliases MUST NOT exceed 255 bytes (including the ``#`` sigil and the domain).
Room aliases MUST NOT exceed 255 bytes (including the ``#`` sigil and the
domain).
.. TODO-spec
- Need to specify precise grammar for Room Aliases. https://matrix.org/jira/browse/SPEC-391

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