Provided by: libmongoc-doc_1.30.4-1ubuntu1_all 
SYNOPSIS
typedef struct _mongoc_uri_t mongoc_uri_t;
DESCRIPTION
mongoc_uri_t provides an abstraction on top of the MongoDB connection URI format. It provides
standardized parsing as well as convenience methods for extracting useful information such as replica
hosts or authorization information.
See Connection String URI Reference on the MongoDB website for more information.
FORMAT
mongodb[+srv]:// <1>
[username:password@] <2>
host1 <3>
[:port1] <4>
[,host2[:port2],...[,hostN[:portN]]] <5>
[/[database] <6>
[?options]] <7>
1. "mongodb" is the specifier of the MongoDB protocol. Use "mongodb+srv" with a single service name in
place of "host1" to specify the initial list of servers with an SRV record.
2. An optional username and password.
3. The only required part of the uri. This specifies either a hostname, IPv4 address, IPv6 address
enclosed in "[" and "]", or UNIX domain socket.
4. An optional port number. Defaults to :27017.
5. Extra optional hosts and ports. You would specify multiple hosts, for example, for connections to
replica sets.
6. The name of the database to authenticate if the connection string includes authentication credentials.
If /database is not specified and the connection string includes credentials, defaults to the 'admin'
database.
7. Connection specific options.
NOTE:
Option names are case-insensitive. Do not repeat the same option (e.g.
"mongodb://localhost/db?opt=value1&OPT=value2") since this may have unexpected results.
The MongoDB C Driver exposes constants for each supported connection option. These constants make it
easier to discover connection options, but their string values can be used as well.
For example, the following calls are equal.
uri = mongoc_uri_new ("mongodb://localhost/?" MONGOC_URI_APPNAME "=applicationName");
uri = mongoc_uri_new ("mongodb://localhost/?appname=applicationName");
uri = mongoc_uri_new ("mongodb://localhost/?appName=applicationName");
REPLICA SET EXAMPLE
To describe a connection to a replica set named 'test' with the following mongod hosts:
• db1.example.com on port 27017
• db2.example.com on port 2500
You would use a connection string that resembles the following.
mongodb://db1.example.com,db2.example.com:2500/?replicaSet=test
SRV EXAMPLE
If you have configured an SRV record with a name like "_mongodb._tcp.server.example.com" whose records
are a list of one or more MongoDB server hostnames, use a connection string like this:
uri = mongoc_uri_new ("mongodb+srv://server.example.com/?replicaSet=rs&appName=applicationName");
The driver prefixes the service name with "_mongodb._tcp.", then performs a DNS SRV query to resolve the
service name to one or more hostnames. If this query succeeds, the driver performs a DNS TXT query on the
service name (without the "_mongodb._tcp" prefix) for additional URI options configured as TXT records.
On Unix, the MongoDB C Driver relies on libresolv to look up SRV and TXT records. If libresolv is
unavailable, then using a "mongodb+srv" URI will cause an error. If your libresolv lacks res_nsearch then
the driver will fall back to res_search, which is not thread-safe.
Set the environment variable MONGOC_EXPERIMENTAL_SRV_PREFER_TCP to prefer TCP for the initial queries.
The environment variable is ignored for res_search. Large DNS responses over UDP may be truncated due to
UDP size limitations. DNS resolvers are expected to retry over TCP if the UDP response indicates
truncation. Some observed DNS environments do not set the truncation flag (TC), preventing the TCP retry.
This environment variable is currently experimental and subject to change.
IPV4 AND IPV6
If connecting to a hostname that has both IPv4 and IPv6 DNS records, the behavior follows RFC-6555. A
connection to the IPv6 address is attempted first. If IPv6 fails, then a connection is attempted to the
IPv4 address. If the connection attempt to IPv6 does not complete within 250ms, then IPv4 is tried in
parallel. Whichever succeeds connection first cancels the other. The successful DNS result is cached for
10 minutes.
As a consequence, attempts to connect to a mongod only listening on IPv4 may be delayed if there are both
A (IPv4) and AAAA (IPv6) DNS records associated with the host.
To avoid a delay, configure hostnames to match the MongoDB configuration. That is, only create an A
record if the mongod is only listening on IPv4.
CONNECTION OPTIONS
┌─────────────────────────────────┬──────────────────────┬────────────────────────┬─────────────────────────────────────┐
├─────────────────────────────────┼──────────────────────┼────────────────────────┼─────────────────────────────────────┤
├─────────────────────────────────┼──────────────────────┼────────────────────────┼─────────────────────────────────────┤
├─────────────────────────────────┼──────────────────────┼────────────────────────┼─────────────────────────────────────┤
├─────────────────────────────────┼──────────────────────┼────────────────────────┼─────────────────────────────────────┤
│ │ │ │ mongoc_client_set_ssl_opts() │
│ │ │ │ mongoc_client_pool_set_ssl_opts().) │
├─────────────────────────────────┼──────────────────────┼────────────────────────┼─────────────────────────────────────┤
├─────────────────────────────────┼──────────────────────┼────────────────────────┼─────────────────────────────────────┤
├─────────────────────────────────┼──────────────────────┼────────────────────────┼─────────────────────────────────────┤
├─────────────────────────────────┼──────────────────────┼────────────────────────┼─────────────────────────────────────┤
├─────────────────────────────────┼──────────────────────┼────────────────────────┼─────────────────────────────────────┤
├─────────────────────────────────┼──────────────────────┼────────────────────────┼─────────────────────────────────────┤
├─────────────────────────────────┼──────────────────────┼────────────────────────┼─────────────────────────────────────┤
└─────────────────────────────────┴──────────────────────┴────────────────────────┴─────────────────────────────────────┘
WARNING:
Setting any of the *timeoutMS options above to either 0 or a negative value is discouraged due to
unspecified and inconsistent behavior. The "default value" historically specified as a fallback for 0
or a negative value is NOT related to the default values for the *timeoutMS options documented above.
The meaning of a timeout of 0 or a negative value may vary depending on the operation being executed,
even when specified by the same URI option. To specify the documented default value for a *timeoutMS
option, use the MONGOC_DEFAULT_* constants defined in mongoc-client.h instead.
AUTHENTICATION OPTIONS
┌────────────────────────────────────┬─────────────────────────┬──────────────────────────────┐
│ Constant │ Key │ Description │
├────────────────────────────────────┼─────────────────────────┼──────────────────────────────┤
│ MONGOC_URI_AUTHMECHANISM │ authmechanism │ Specifies the mechanism to │
│ │ │ use when authenticating as │
│ │ │ the provided user. See ‐ │
│ │ │ Authentication for supported │
│ │ │ values. │
├────────────────────────────────────┼─────────────────────────┼──────────────────────────────┤
│ MONGOC_URI_AUTHMECHANISMPROPERTIES │ authmechanismproperties │ Certain authentication │
│ │ │ mechanisms have additional │
│ │ │ options that can be │
│ │ │ configured. These options │
│ │ │ should be provided as comma │
│ │ │ separated │
│ │ │ option_key:option_value pair │
│ │ │ and provided as │
│ │ │ authMechanismProperties. │
│ │ │ Specifying the same │
│ │ │ option_key multiple times │
│ │ │ has undefined behavior. │
├────────────────────────────────────┼─────────────────────────┼──────────────────────────────┤
│ MONGOC_URI_AUTHSOURCE │ authsource │ The authSource defines the │
│ │ │ database that should be used │
│ │ │ to authenticate to. It is │
│ │ │ unnecessary to provide this │
│ │ │ option the database name is │
│ │ │ the same as the database │
│ │ │ used in the URI. │
└────────────────────────────────────┴─────────────────────────┴──────────────────────────────┘
Mechanism Properties
┌─────────────────────────────────┬──────────────────────┬──────────────────────────────┐
│ Constant │ Key │ Description │
├─────────────────────────────────┼──────────────────────┼──────────────────────────────┤
│ MONGOC_URI_CANONICALIZEHOSTNAME │ canonicalizehostname │ Use the canonical hostname │
│ │ │ of the service, rather than │
│ │ │ its configured alias, when │
│ │ │ authenticating with │
│ │ │ Cyrus-SASL Kerberos. │
├─────────────────────────────────┼──────────────────────┼──────────────────────────────┤
│ MONGOC_URI_GSSAPISERVICENAME │ gssapiservicename │ Use alternative service │
│ │ │ name. The default is │
│ │ │ mongodb. │
└─────────────────────────────────┴──────────────────────┴──────────────────────────────┘
TLS OPTIONS
┌─────────────────────────────────────────────────┬──────────────────────────────────────┬────────────────────────────────────────┐
├─────────────────────────────────────────────────┼──────────────────────────────────────┼────────────────────────────────────────┤
├─────────────────────────────────────────────────┼──────────────────────────────────────┼────────────────────────────────────────┤
├─────────────────────────────────────────────────┼──────────────────────────────────────┼────────────────────────────────────────┤
├─────────────────────────────────────────────────┼──────────────────────────────────────┼────────────────────────────────────────┤
├─────────────────────────────────────────────────┼──────────────────────────────────────┼────────────────────────────────────────┤
├─────────────────────────────────────────────────┼──────────────────────────────────────┼────────────────────────────────────────┤
├─────────────────────────────────────────────────┼──────────────────────────────────────┼────────────────────────────────────────┤
├─────────────────────────────────────────────────┼──────────────────────────────────────┼────────────────────────────────────────┤
├─────────────────────────────────────────────────┼──────────────────────────────────────┼────────────────────────────────────────┤
└─────────────────────────────────────────────────┴──────────────────────────────────────┴────────────────────────────────────────┘
See Configuring TLS for details about these options and about building libmongoc with TLS support.
DEPRECATED SSL OPTIONS
The following options have been deprecated and may be removed from future releases of libmongoc.
┌────────────────────────────────────────────┬─────────────────────────────────┬──────────────────────────────────────────┬─────────────────────────────┐
├────────────────────────────────────────────┼─────────────────────────────────┼──────────────────────────────────────────┼─────────────────────────────┤
├────────────────────────────────────────────┼─────────────────────────────────┼──────────────────────────────────────────┼─────────────────────────────┤
├────────────────────────────────────────────┼─────────────────────────────────┼──────────────────────────────────────────┼─────────────────────────────┤
├────────────────────────────────────────────┼─────────────────────────────────┼──────────────────────────────────────────┼─────────────────────────────┤
├────────────────────────────────────────────┼─────────────────────────────────┼──────────────────────────────────────────┼─────────────────────────────┤
├────────────────────────────────────────────┼─────────────────────────────────┼──────────────────────────────────────────┼─────────────────────────────┤
└────────────────────────────────────────────┴─────────────────────────────────┴──────────────────────────────────────────┴─────────────────────────────┘
SERVER DISCOVERY, MONITORING, AND SELECTION OPTIONS
Clients in a mongoc_client_pool_t share a topology scanner that runs on a background thread. The thread
wakes every heartbeatFrequencyMS (default 10 seconds) to scan all MongoDB servers in parallel. Whenever
an application operation requires a server that is not known--for example, if there is no known primary
and your application attempts an insert--the thread rescans all servers every half-second. In this
situation the pooled client waits up to serverSelectionTimeoutMS (default 30 seconds) for the thread to
find a server suitable for the operation, then returns an error with domain
MONGOC_ERROR_SERVER_SELECTION.
Technically, the total time an operation may wait while a pooled client scans the topology is controlled
both by serverSelectionTimeoutMS and connectTimeoutMS. The longest wait occurs if the last scan begins
just at the end of the selection timeout, and a slow or down server requires the full connection timeout
before the client gives up.
A non-pooled client is single-threaded. Every heartbeatFrequencyMS, it blocks the next application
operation while it does a parallel scan. This scan takes as long as needed to check the slowest server:
roughly connectTimeoutMS. Therefore the default heartbeatFrequencyMS for single-threaded clients is
greater than for pooled clients: 60 seconds.
By default, single-threaded (non-pooled) clients scan only once when an operation requires a server that
is not known. If you attempt an insert and there is no known primary, the client checks all servers once
trying to find it, then succeeds or returns an error with domain MONGOC_ERROR_SERVER_SELECTION. But if
you set serverSelectionTryOnce to "false", the single-threaded client loops, checking all servers every
half-second, until serverSelectionTimeoutMS.
The total time an operation may wait for a single-threaded client to scan the topology is determined by
connectTimeoutMS in the try-once case, or serverSelectionTimeoutMS and connectTimeoutMS if
serverSelectionTryOnce is set "false".
┌─────────────────────────────────────┬──────────────────────────┬──────────────────────────────┐
│ Constant │ Key │ Description │
├─────────────────────────────────────┼──────────────────────────┼──────────────────────────────┤
│ MONGOC_URI_HEARTBEATFREQUENCYMS │ heartbeatfrequencyms │ The interval between server │
│ │ │ monitoring checks. Defaults │
│ │ │ to 10,000ms (10 seconds) in │
│ │ │ pooled (multi-threaded) │
│ │ │ mode, 60,000ms (60 seconds) │
│ │ │ in non-pooled mode │
│ │ │ (single-threaded). │
├─────────────────────────────────────┼──────────────────────────┼──────────────────────────────┤
│ MONGOC_URI_SERVERSELECTIONTIMEOUTMS │ serverselectiontimeoutms │ A timeout in milliseconds to │
│ │ │ block for server selection │
│ │ │ before throwing an │
│ │ │ exception. The default is │
│ │ │ 30,0000ms (30 seconds). │
├─────────────────────────────────────┼──────────────────────────┼──────────────────────────────┤
│ MONGOC_URI_SERVERSELECTIONTRYONCE │ serverselectiontryonce │ If "true", the driver scans │
│ │ │ the topology exactly once │
│ │ │ after server selection │
│ │ │ fails, then either selects a │
│ │ │ server or returns an error. │
│ │ │ If it is false, then the │
│ │ │ driver repeatedly searches │
│ │ │ for a suitable server for up │
│ │ │ to serverSelectionTimeoutMS │
│ │ │ milliseconds (pausing a half │
│ │ │ second between attempts). │
│ │ │ The default for │
│ │ │ serverSelectionTryOnce is │
│ │ │ "false" for pooled clients, │
│ │ │ otherwise "true". Pooled │
│ │ │ clients ignore │
│ │ │ serverSelectionTryOnce; they │
│ │ │ signal the thread to rescan │
│ │ │ the topology every │
│ │ │ half-second until │
│ │ │ serverSelectionTimeoutMS │
│ │ │ expires. │
├─────────────────────────────────────┼──────────────────────────┼──────────────────────────────┤
│ MONGOC_URI_SOCKETCHECKINTERVALMS │ socketcheckintervalms │ Only applies to single │
│ │ │ threaded clients. If a │
│ │ │ socket has not been used │
│ │ │ within this time, its │
│ │ │ connection is checked with a │
│ │ │ quick "hello" call before it │
│ │ │ is used again. Defaults to │
│ │ │ 5,000ms (5 seconds). │
├─────────────────────────────────────┼──────────────────────────┼──────────────────────────────┤
│ MONGOC_URI_DIRECTCONNECTION │ directconnection │ If "true", the driver │
│ │ │ connects to a single server │
│ │ │ directly and will not │
│ │ │ monitor additional servers. │
│ │ │ If "false", the driver │
│ │ │ connects based on the │
│ │ │ presence and value of the │
│ │ │ replicaSet option. │
└─────────────────────────────────────┴──────────────────────────┴──────────────────────────────┘
Setting any of the *TimeoutMS options above to 0 will be interpreted as "use the default value".
CONNECTION POOL OPTIONS
These options govern the behavior of a mongoc_client_pool_t. They are ignored by a non-pooled
mongoc_client_t.
┌───────────────────────────────┬────────────────────┬──────────────────────────────┐
│ Constant │ Key │ Description │
├───────────────────────────────┼────────────────────┼──────────────────────────────┤
│ MONGOC_URI_MAXPOOLSIZE │ maxpoolsize │ The maximum number of │
│ │ │ clients created by a │
│ │ │ mongoc_client_pool_t total │
│ │ │ (both in the pool and │
│ │ │ checked out). The default │
│ │ │ value is 100. Once it is │
│ │ │ reached, │
│ │ │ mongoc_client_pool_pop() │
│ │ │ blocks until another thread │
│ │ │ pushes a client. │
├───────────────────────────────┼────────────────────┼──────────────────────────────┤
│ MONGOC_URI_MINPOOLSIZE │ minpoolsize │ Deprecated. This option's │
│ │ │ behavior does not match its │
│ │ │ name, and its actual │
│ │ │ behavior will likely hurt │
│ │ │ performance. │
├───────────────────────────────┼────────────────────┼──────────────────────────────┤
│ MONGOC_URI_MAXIDLETIMEMS │ maxidletimems │ Not implemented. │
├───────────────────────────────┼────────────────────┼──────────────────────────────┤
│ MONGOC_URI_WAITQUEUEMULTIPLE │ waitqueuemultiple │ Not implemented. │
├───────────────────────────────┼────────────────────┼──────────────────────────────┤
│ MONGOC_URI_WAITQUEUETIMEOUTMS │ waitqueuetimeoutms │ The maximum time to wait for │
│ │ │ a client to become available │
│ │ │ from the pool. │
└───────────────────────────────┴────────────────────┴──────────────────────────────┘
WRITE CONCERN OPTIONS
┌───────────────────────┬────────────┬──────────────────────────────┐
│ Constant │ Key │ Description │
├───────────────────────┼────────────┼──────────────────────────────┤
│ MONGOC_URI_W │ w │ Determines the write concern │
│ │ │ (guarantee). Valid values: │
│ │ │ │
│ │ │ • 0 = The driver will │
│ │ │ not acknowledge │
│ │ │ write operations │
│ │ │ but will pass or │
│ │ │ handle any network │
│ │ │ and socket errors │
│ │ │ that it receives to │
│ │ │ the client. If you │
│ │ │ disable write │
│ │ │ concern but enable │
│ │ │ the getLastError │
│ │ │ command’s w option, │
│ │ │ w overrides the w │
│ │ │ option. │
│ │ │ │
│ │ │ • 1 = Provides basic │
│ │ │ acknowledgement of │
│ │ │ write operations. │
│ │ │ By specifying 1, │
│ │ │ you require that a │
│ │ │ standalone mongod │
│ │ │ instance, or the │
│ │ │ primary for replica │
│ │ │ sets, acknowledge │
│ │ │ all write │
│ │ │ operations. For │
│ │ │ drivers released │
│ │ │ after the default │
│ │ │ write concern │
│ │ │ change, this is the │
│ │ │ default write │
│ │ │ concern setting. │
│ │ │ │
│ │ │ • majority = For │
│ │ │ replica sets, if │
│ │ │ you specify the │
│ │ │ special majority │
│ │ │ value to w option, │
│ │ │ write operations │
│ │ │ will only return │
│ │ │ successfully after │
│ │ │ a majority of the │
│ │ │ configured replica │
│ │ │ set members have │
│ │ │ acknowledged the │
│ │ │ write operation. │
│ │ │ │
│ │ │ • n = For replica │
│ │ │ sets, if you │
│ │ │ specify a number n │
│ │ │ greater than 1, │
│ │ │ operations with │
│ │ │ this write concern │
│ │ │ return only after n │
│ │ │ members of the set │
│ │ │ have acknowledged │
│ │ │ the write. If you │
│ │ │ set n to a number │
│ │ │ that is greater │
│ │ │ than the number of │
│ │ │ available set │
│ │ │ members or members │
│ │ │ that hold data, │
│ │ │ MongoDB will wait, │
│ │ │ potentially │
│ │ │ indefinitely, for │
│ │ │ these members to │
│ │ │ become available. │
│ │ │ │
│ │ │ • tags = For replica │
│ │ │ sets, you can │
│ │ │ specify a tag set │
│ │ │ to require that all │
│ │ │ members of the set │
│ │ │ that have these │
│ │ │ tags configured │
│ │ │ return confirmation │
│ │ │ of the write │
│ │ │ operation. │
├───────────────────────┼────────────┼──────────────────────────────┤
│ MONGOC_URI_WTIMEOUTMS │ wtimeoutms │ The time in milliseconds to │
│ │ │ wait for replication to │
│ │ │ succeed, as specified in the │
│ │ │ w option, before timing out. │
│ │ │ When wtimeoutMS is 0, write │
│ │ │ operations will never time │
│ │ │ out. │
├───────────────────────┼────────────┼──────────────────────────────┤
│ MONGOC_URI_JOURNAL │ journal │ Controls whether write │
│ │ │ operations will wait until │
│ │ │ the mongod acknowledges the │
│ │ │ write operations and commits │
│ │ │ the data to the on disk │
│ │ │ journal. │
│ │ │ │
│ │ │ • true = Enables │
│ │ │ journal commit │
│ │ │ acknowledgement │
│ │ │ write concern. │
│ │ │ Equivalent to │
│ │ │ specifying the │
│ │ │ getLastError │
│ │ │ command with the j │
│ │ │ option enabled. │
│ │ │ │
│ │ │ • false = Does not │
│ │ │ require that mongod │
│ │ │ commit write │
│ │ │ operations to the │
│ │ │ journal before │
│ │ │ acknowledging the │
│ │ │ write operation. │
│ │ │ This is the default │
│ │ │ option for the │
│ │ │ journal parameter. │
└───────────────────────┴────────────┴──────────────────────────────┘
READ CONCERN OPTIONS
┌─────────────────────────────┬──────────────────┬──────────────────────────────┐
│ Constant │ Key │ Description │
├─────────────────────────────┼──────────────────┼──────────────────────────────┤
│ MONGOC_URI_READCONCERNLEVEL │ readconcernlevel │ The level of isolation for │
│ │ │ read operations. If the │
│ │ │ level is left unspecified, │
│ │ │ the server default will be │
│ │ │ used. See readConcern in the │
│ │ │ MongoDB Manual for details. │
└─────────────────────────────┴──────────────────┴──────────────────────────────┘
READ PREFERENCE OPTIONS
When connected to a replica set, the driver chooses which member to query using the read preference:
1. Choose members whose type matches "readPreference".
2. From these, if there are any tags sets configured, choose members matching the first tag set. If there
are none, fall back to the next tag set and so on, until some members are chosen or the tag sets are
exhausted.
3. From the chosen servers, distribute queries randomly among the server with the fastest round-trip
times. These include the server with the fastest time and any whose round-trip time is no more than
"localThresholdMS" slower.
┌────────────────────────────────┬─────────────────────┬──────────────────────────────┐
│ Constant │ Key │ Description │
├────────────────────────────────┼─────────────────────┼──────────────────────────────┤
│ MONGOC_URI_READPREFERENCE │ readpreference │ Specifies the replica set │
│ │ │ read preference for this │
│ │ │ connection. This setting │
│ │ │ overrides any secondaryOk │
│ │ │ value. The read preference │
│ │ │ values are the following: │
│ │ │ │
│ │ │ • primary (default) │
│ │ │ │
│ │ │ • primaryPreferred │
│ │ │ │
│ │ │ • secondary │
│ │ │ │
│ │ │ • secondaryPreferred │
│ │ │ │
│ │ │ • nearest │
├────────────────────────────────┼─────────────────────┼──────────────────────────────┤
│ MONGOC_URI_READPREFERENCETAGS │ readpreferencetags │ A representation of a tag │
│ │ │ set. See also Tag Sets. │
├────────────────────────────────┼─────────────────────┼──────────────────────────────┤
│ MONGOC_URI_LOCALTHRESHOLDMS │ localthresholdms │ How far to distribute │
│ │ │ queries, beyond the server │
│ │ │ with the fastest round-trip │
│ │ │ time. By default, only │
│ │ │ servers within 15ms of the │
│ │ │ fastest round-trip time │
│ │ │ receive queries. │
├────────────────────────────────┼─────────────────────┼──────────────────────────────┤
│ MONGOC_URI_MAXSTALENESSSECONDS │ maxstalenessseconds │ The maximum replication lag, │
│ │ │ in wall clock time, that a │
│ │ │ secondary can suffer and │
│ │ │ still be eligible. The │
│ │ │ smallest allowed value for │
│ │ │ maxStalenessSeconds is 90 │
│ │ │ seconds. │
└────────────────────────────────┴─────────────────────┴──────────────────────────────┘
NOTE:
When connecting to more than one mongos, libmongoc's localThresholdMS applies only to the selection of
mongos servers. The threshold for selecting among replica set members in shards is controlled by the ‐
mongos's localThreshold command line option.
LEGACY OPTIONS
For historical reasons, the following options are available. They should however not be used.
┌─────────────────┬──────┬──────────────────────────────┐
│ Constant │ Key │ Description │
├─────────────────┼──────┼──────────────────────────────┤
│ MONGOC_URI_SAFE │ safe │ {true|false} Same as w={1|0} │
└─────────────────┴──────┴──────────────────────────────┘
AUTHOR
MongoDB, Inc
COPYRIGHT
2009-present, MongoDB, Inc.
1.30.4 Jun 08, 2025 MONGOC_URI_T(3)