RFC 3433
Entity Sensor Management Information Base
RFC 3433: Entity Sensor Management Information Base 🎀
Okay bestie, so this is RFC 3433 💖 (part 1 of 3 🧚). It's called "Entity Sensor Management Information Base" and it's on the Standards Track 👑. It's dated December 2002 🌸 and it came out of the Network Working Group. The authors are Andy Bierman (Cisco Systems, Inc.), Dan Romascanu (Avaya Inc.), and K.C. Norseth (L-3 Communications) 🫶. The header doesn't list anything it obsoletes or updates 🙈.
Status of this Memo
So this doc is an Internet standards track protocol for the whole Internet community 🌐, and it's literally asking for discussion and suggestions to make it better 💅. For the standardization state and status of this protocol, check the current edition of the "Internet Official Protocol Standards" (STD 1) ✨. Distribution of this memo is unlimited 🦋.
Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved. 🔒
Abstract
This memo is a piece of the Management Information Base (MIB) that network management protocols across the Internet use 💜. It's all about extending the Entity MIB (RFC 2737) with managed objects that give generalized access to physical sensor info, the kind you find in networking gear, like chassis temperature, fan RPM, and power supply voltage 🌡️.
Table of Contents
1 The Internet-Standard Management Framework .................. 2
2 Overview .................................................... 2
2.1 Terms ................................................... 2
2.2 Relationship to the Entity MIB .......................... 2
2.3 Relationship to General Thresholding Mechanisms ......... 3
3 MIB Structure ............................................... 3
4 Definitions ................................................. 4
5 Intellectual Property ....................................... 13
6 Acknowledgements ............................................ 14
7 Normative References ........................................ 14
8 Informative References ...................................... 14
9 Security Considerations ..................................... 15
10 Authors' Addresses .......................................... 16
11 Full Copyright Statement .................................... 171. The Internet-Standard Management Framework 🦋
For a detailed overview of the docs that describe the current Internet-Standard Management Framework, check out section 7 of RFC 3410 [RFC3410] 📚.
Managed objects are accessed via a virtual information store, called the Management Information Base or MIB 🗂️. MIB objects are generally accessed through the Simple Network Management Protocol (SNMP). Objects in the MIB are defined using the mechanisms in the Structure of Management Information (SMI). This memo specifies a MIB module that is compliant to the SMIv2, which is described in STD 58, RFC 2578 [RFC2578], STD 58, RFC 2579 [RFC2579] and STD 58, RFC 2580 [RFC2580] ✨.
2. Overview 🌈
Okay so there's a real need for a standard way to get info about the physical sensors that show up all over networking equipment 🧊. Stuff like the current value of the sensor, its current operational status, and the data units precision linked to the sensor should be represented in a consistent way for any type of sensor 💖.
Physical sensors are represented in the Entity MIB with entPhysicalEntry and an entPhysicalClass value of 'sensor(8)'. The info in the ENTITY-SENSOR-MIB module (defined in this document) is a sparse augmentation of the entPhysicalTable, for entries that represent physical sensors 🎀.
2.1. Terms
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14, RFC 2119. [RFC2119] 📖
2.2. Relationship to the Entity MIB
The MIB objects defined here are a sparse augmentation to the entPhysicalTable in the Entity MIB, for entries where the associated entPhysicalClass object is equal to 'sensor(8)' 🌸. An agent is expected to maintain an entPhySensorEntry with the same entPhysicalIndex value for each entPhysicalEntry representing a physical sensor. Therefore, implementation of the entityPhysicalGroup is required for agents that implement the Entity Sensor MIB 🫶.
2.3. Relationship to General Thresholding Mechanisms
Ngl, there are no specialized sensor value thresholding mechanisms defined in this MIB module 🙅. Instead, it is recommended that a generalized thresholding MIB be used for this purpose, like the mechanisms in the Alarm and Events groups of the Remote Network Monitoring MIB [RFC2819] 🍓.
3. MIB Structure 🧚
The Entity Sensor MIB has a single group called the entitySensorValueGroup, which lets objects convey the current value and status of a physical sensor 💜.
That group has one table, called the entPhySensorTable, and it provides a small number of read-only objects:
entPhySensorType: This object identifies the type of data units associated with the sensor value.entPhySensorScale: This object identifies the (power of 10) scaling factor associated with the sensor value.entPhySensorPrecision: This object identifies the number of decimal places of precision associated with the sensor value.entPhySensorValue: This object identifies the current value of the sensor.entPhySensorOperStatus: This object identifies the current operational status of the sensor (as it's known to the agent).entPhySensorUnitsDisplay: This object provides a textual description of the data units represented by theentPhySensorTypeandentPhySensorScaleobjects.entPhySensorValueTimeStamp: This object identifies the value ofsysUpTimeat the time the agent last updated the information in the entry. This object is only relevant if the agent uses a polling implementation strategy (i.e., the associatedentPhySensorValueUpdateRateobject is greater than zero) ⏱️.entPhySensorValueUpdateRate: This object indicates the nature of the agent implementation of theentPhySensorEntry, and contains the (possibly estimated) number of milliseconds that elapse between polling updates of the information in the associated entry. The value zero indicates that the agent always return current data for the entry (as opposed to the data as it was at the last polling interval) 🔥.
4. Definitions 💜
Now the actual MIB 💅. Here's the module header, the object identifiers, and the first textual convention, copied exactly:
ENTITY-SENSOR-MIB DEFINITIONS ::= BEGIN
IMPORTS
MODULE-IDENTITY, OBJECT-TYPE,
Integer32, Unsigned32, mib-2
FROM SNMPv2-SMI
MODULE-COMPLIANCE, OBJECT-GROUP
FROM SNMPv2-CONF
TEXTUAL-CONVENTION, TimeStamp
FROM SNMPv2-TC
entPhysicalIndex, entityPhysicalGroup
FROM ENTITY-MIB
SnmpAdminString
FROM SNMP-FRAMEWORK-MIB;
entitySensorMIB MODULE-IDENTITY
LAST-UPDATED "200212160000Z"
ORGANIZATION "IETF Entity MIB Working Group"
CONTACT-INFO
" Andy Bierman
Cisco Systems, Inc.
Tel: +1 408-527-3711
E-mail: abierman@cisco.com
Postal: 170 West Tasman Drive
San Jose, CA USA 95134
Dan Romascanu
Avaya Inc.
Tel: +972-3-645-8414
Email: dromasca@avaya.com
Postal: Atidim technology Park, Bldg. #3
Tel Aviv, Israel, 61131
K.C. Norseth
L-3 Communications
Tel: +1 801-594-2809
Email: kenyon.c.norseth@L-3com.com
Postal: 640 N. 2200 West.
Salt Lake City, Utah 84116-0850
Send comments to <entmib@ietf.org>
Mailing list subscription info:
http://www.ietf.org/mailman/listinfo/entmib "
DESCRIPTION
"This module defines Entity MIB extensions for physical
sensors.
Copyright (C) The Internet Society (2002). This version
of this MIB module is part of RFC 3433; see the RFC
itself for full legal notices."
REVISION "200212160000Z"
DESCRIPTION
"Initial version of the Entity Sensor MIB module, published
as RFC 3433."
::= { mib-2 99 }
entitySensorObjects OBJECT IDENTIFIER
::= { entitySensorMIB 1 }
-- entitySensorNotifications OBJECT IDENTIFIER
-- ::= { entitySensorMIB 2 }
entitySensorConformance OBJECT IDENTIFIER
::= { entitySensorMIB 3 }
--
-- Textual Conventions
--
EntitySensorDataType ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"An object using this data type represents the Entity Sensor
measurement data type associated with a physical sensor
value. The actual data units are determined by examining an
object of this type together with the associated
EntitySensorDataScale object.
An object of this type SHOULD be defined together with
objects of type EntitySensorDataScale and
EntitySensorPrecision. Together, associated objects of
these three types are used to identify the semantics of an
object of type EntitySensorValue.
Valid values are:
other(1): a measure other than those listed below
unknown(2): unknown measurement, or arbitrary,
relative numbers
voltsAC(3): electric potential
voltsDC(4): electric potential
amperes(5): electric current
watts(6): power
hertz(7): frequency
celsius(8): temperature
percentRH(9): percent relative humidity
rpm(10): shaft revolutions per minute
cmm(11),: cubic meters per minute (airflow)
truthvalue(12): value takes { true(1), false(2) }
"
SYNTAX INTEGER {
other(1),
unknown(2),
voltsAC(3),
voltsDC(4),
amperes(5),
watts(6),
hertz(7),
celsius(8),
percentRH(9),
rpm(10),
cmm(11),
truthvalue(12)
}okay so the textual conventions are the dictionary the whole MIB runs on 📖✨ bestie, watch how the three types team up 💅
EntitySensorDataScale ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"An object using this data type represents a data scaling
factor, represented with an International System of Units
(SI) prefix. The actual data units are determined by
examining an object of this type together with the
associated EntitySensorDataType object.
An object of this type SHOULD be defined together with
objects of type EntitySensorDataType and
EntitySensorPrecision. Together, associated objects of
these three types are used to identify the semantics of an
object of type EntitySensorValue."
REFERENCE
"The International System of Units (SI),
National Institute of Standards and Technology,
Spec. Publ. 330, August 1991."
SYNTAX INTEGER {
yocto(1), -- 10^-24
zepto(2), -- 10^-21
atto(3), -- 10^-18
femto(4), -- 10^-15
pico(5), -- 10^-12
nano(6), -- 10^-9
micro(7), -- 10^-6
milli(8), -- 10^-3
units(9), -- 10^0
kilo(10), -- 10^3
mega(11), -- 10^6
giga(12), -- 10^9
tera(13), -- 10^12
exa(14), -- 10^15
peta(15), -- 10^18
zetta(16), -- 10^21
yotta(17) -- 10^24
}
EntitySensorPrecision ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"An object using this data type represents a sensor
precision range.
An object of this type SHOULD be defined together with
objects of type EntitySensorDataType and
EntitySensorDataScale. Together, associated objects of
these three types are used to identify the semantics of an
object of type EntitySensorValue.
If an object of this type contains a value in the range 1 to
9, it represents the number of decimal places in the
fractional part of an associated EntitySensorValue fixed-
point number.
If an object of this type contains a value in the range -8
to -1, it represents the number of accurate digits in the
associated EntitySensorValue fixed-point number.
The value zero indicates the associated EntitySensorValue
object is not a fixed-point number.
Agent implementors must choose a value for the associated
EntitySensorPrecision object so that the precision and
accuracy of the associated EntitySensorValue object is
correctly indicated.
For example, a physical entity representing a temperature
sensor that can measure 0 degrees to 100 degrees C in 0.1
degree increments, +/- 0.05 degrees, would have an
EntitySensorPrecision value of '1', an EntitySensorDataScale
value of 'units(9)', and an EntitySensorValue ranging from
'0' to '1000'. The EntitySensorValue would be interpreted
as 'degrees C * 10'."
SYNTAX Integer32 (-8..9)
EntitySensorValue ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"An object using this data type represents an Entity Sensor
value.
An object of this type SHOULD be defined together with
objects of type EntitySensorDataType, EntitySensorDataScale
and EntitySensorPrecision. Together, associated objects of
those three types are used to identify the semantics of an
object of this data type.
The semantics of an object using this data type are
determined by the value of the associated
EntitySensorDataType object.
If the associated EntitySensorDataType object is equal to
'voltsAC(3)', 'voltsDC(4)', 'amperes(5)', 'watts(6),
'hertz(7)', 'celsius(8)', or 'cmm(11)', then an object of
this type MUST contain a fixed point number ranging from
-999,999,999 to +999,999,999. The value -1000000000
indicates an underflow error. The value +1000000000
indicates an overflow error. The EntitySensorPrecision
indicates how many fractional digits are represented in the
associated EntitySensorValue object.
If the associated EntitySensorDataType object is equal to
'percentRH(9)', then an object of this type MUST contain a
number ranging from 0 to 100.
If the associated EntitySensorDataType object is equal to
'rpm(10)', then an object of this type MUST contain a number
ranging from -999,999,999 to +999,999,999.
If the associated EntitySensorDataType object is equal to
'truthvalue(12)', then an object of this type MUST contain
either the value 'true(1)' or the value 'false(2)'.
If the associated EntitySensorDataType object is equal to
'other(1)' or unknown(2)', then an object of this type MUST
contain a number ranging from -1000000000 to 1000000000."
SYNTAX Integer32 (-1000000000..1000000000)
EntitySensorStatus ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"An object using this data type represents the operational
status of a physical sensor.
The value 'ok(1)' indicates that the agent can obtain the
sensor value.
The value 'unavailable(2)' indicates that the agent
presently cannot obtain the sensor value.
The value 'nonoperational(3)' indicates that the agent
believes the sensor is broken. The sensor could have a hard
failure (disconnected wire), or a soft failure such as out-
of-range, jittery, or wildly fluctuating readings."
SYNTAX INTEGER {
ok(1),
unavailable(2),
nonoperational(3)
}
--
-- Entity Sensor Table
--
entPhySensorTable OBJECT-TYPE
SYNTAX SEQUENCE OF EntPhySensorEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"This table contains one row per physical sensor represented
by an associated row in the entPhysicalTable."
::= { entitySensorObjects 1 }
entPhySensorEntry OBJECT-TYPE
SYNTAX EntPhySensorEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"Information about a particular physical sensor.
An entry in this table describes the present reading of a
sensor, the measurement units and scale, and sensor
operational status.
Entries are created in this table by the agent. An entry
for each physical sensor SHOULD be created at the same time
as the associated entPhysicalEntry. An entry SHOULD be
destroyed if the associated entPhysicalEntry is destroyed."
INDEX { entPhysicalIndex } -- SPARSE-AUGMENTS
::= { entPhySensorTable 1 }
EntPhySensorEntry ::= SEQUENCE {
entPhySensorType EntitySensorDataType,
entPhySensorScale EntitySensorDataScale,
entPhySensorPrecision EntitySensorPrecision,
entPhySensorValue EntitySensorValue,
entPhySensorOperStatus EntitySensorStatus,
entPhySensorUnitsDisplay SnmpAdminString,
entPhySensorValueTimeStamp TimeStamp,
entPhySensorValueUpdateRate Unsigned32
}
entPhySensorType OBJECT-TYPE
SYNTAX EntitySensorDataType
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The type of data returned by the associated
entPhySensorValue object.
This object SHOULD be set by the agent during entry
creation, and the value SHOULD NOT change during operation."
::= { entPhySensorEntry 1 }
entPhySensorScale OBJECT-TYPE
SYNTAX EntitySensorDataScale
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The exponent to apply to values returned by the associated
entPhySensorValue object.
This object SHOULD be set by the agent during entry
creation, and the value SHOULD NOT change during operation."
::= { entPhySensorEntry 2 }
entPhySensorPrecision OBJECT-TYPE
SYNTAX EntitySensorPrecision
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The number of decimal places of precision in fixed-point
sensor values returned by the associated entPhySensorValue
object.
This object SHOULD be set to '0' when the associated
entPhySensorType value is not a fixed-point type: e.g.,
'percentRH(9)', 'rpm(10)', 'cmm(11)', or 'truthvalue(12)'.
This object SHOULD be set by the agent during entry
creation, and the value SHOULD NOT change during operation."
::= { entPhySensorEntry 3 }
entPhySensorValue OBJECT-TYPE
SYNTAX EntitySensorValue
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The most recent measurement obtained by the agent for this
sensor.
To correctly interpret the value of this object, the
associated entPhySensorType, entPhySensorScale, and
entPhySensorPrecision objects must also be examined."
::= { entPhySensorEntry 4 }
entPhySensorOperStatus OBJECT-TYPE
SYNTAX EntitySensorStatus
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The operational status of the sensor."
::= { entPhySensorEntry 5 }
entPhySensorUnitsDisplay OBJECT-TYPE
SYNTAX SnmpAdminString
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"A textual description of the data units that should be used
in the display of entPhySensorValue."
::= { entPhySensorEntry 6 }
entPhySensorValueTimeStamp OBJECT-TYPE
SYNTAX TimeStamp
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The value of sysUpTime at the time the status and/or value
of this sensor was last obtained by the agent."
::= { entPhySensorEntry 7 }
entPhySensorValueUpdateRate OBJECT-TYPE
SYNTAX Unsigned32
UNITS "milliseconds"
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"An indication of the frequency that the agent updates the
associated entPhySensorValue object, representing in
milliseconds.
The value zero indicates:
- the sensor value is updated on demand (e.g.,
when polled by the agent for a get-request),
- the sensor value is updated when the sensor
value changes (event-driven),
- the agent does not know the update rate.
"
::= { entPhySensorEntry 8 }
--
-- Conformance Section
--
entitySensorCompliances OBJECT IDENTIFIER
::= { entitySensorConformance 1 }
entitySensorGroups OBJECT IDENTIFIER
::= { entitySensorConformance 2 }
entitySensorCompliance MODULE-COMPLIANCE
STATUS current
DESCRIPTION
"Describes the requirements for conformance to the Entity
Sensor MIB module."
MODULE -- this module
MANDATORY-GROUPS { entitySensorValueGroup }
MODULE ENTITY-MIB
MANDATORY-GROUPS { entityPhysicalGroup }
::= { entitySensorCompliances 1 }
-- Object GroupsentitySensorValueGroup OBJECT-GROUP
OBJECTS {
entPhySensorType,
entPhySensorScale,
entPhySensorPrecision,
entPhySensorValue,
entPhySensorOperStatus,
entPhySensorUnitsDisplay,
entPhySensorValueTimeStamp,
entPhySensorValueUpdateRate
}
STATUS current
DESCRIPTION
"A collection of objects representing physical entity sensor
information."
::= { entitySensorGroups 1 }
END5. Intellectual Property ⚖️
okay so the IETF is basically saying it doesn't take a side on whether any intellectual property or other rights that someone might claim over the tech in this doc are valid or how far they reach 🙃 It also doesn't say it's checked for any of those rights, which is very honest of them ngl. If you want the details on their procedures for rights in standards-track and standards-related documents, you go look at BCP-11. Any claims of rights that were made available for publication, plus any assurances of licenses that were promised, or the result of an attempt to get a general license or permission for implementers or users to use those proprietary rights, can be obtained from the IETF Secretariat. Very organised, very tidy 🗂️
The IETF also invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to practice this standard. Send that info to the IETF Executive Director. Main character energy for the whole community to look out for each other 🫶
6. Acknowledgements 🌸
this memo is a product of the Entity MIB working group, and it's based on an existing proprietary MIB module written by Cliff Sojourner. So a real person's work got turned into the open standard. Iconic origin story 👑
7. Normative References 📚
- [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
- [RFC2578] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose, M. and S. Waldbusser, "Structure of Management Information Version 2 (SMIv2)", STD 58, RFC 2578, April 1999.
- [RFC2579] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose, M., and S. Waldbusser, "Textual Conventions for SMIv2", STD 58, RFC 2579, April 1999.
- [RFC2580] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose, M. and S. Waldbusser, "Conformance Statements for SMIv2", STD 58, RFC 2580, April 1999.
- [RFC2737] McCloghrie, K. and A. Bierman, "Entity MIB (Version 2)", RFC 2737, December 1999.
- [RFC3414] Blumenthal, U. and B. Wijnen, "User-based Security Model (USM) for version 3 of the Simple Network Management Protocol (SNMPv3)", STD 62, RFC 3414, December 2002.
- [RFC3415] Wijnen, B., Presuhn, R. and K. McCloghrie, "View-based Access Control Model (VACM) for the Simple Network Management Protocol (SNMP)", STD 62, RFC 3415, December 2002.
8. Informative References 💜
- [RFC2819] Waldbusser, S., "Remote network Monitoring Management Information Base", RFC 2819, May 2000.
- [RFC3410] Case, J., Mundy, R., Partain, D. and B. Stewart, "Introduction and Applicability Statements for Internet-Standard Management Framework", RFC 3410, December 2002.
9. Security Considerations 🚨
okay bestie, this section is SERIOUS 😭 There is one managed object in this MIB that may contain sensitive information, and it's this one:
entPhySensorValueThis object may expose the values of particular physical sensors for a device. So like, the readings themselves can be the sensitive part 👀
SNMPv1 by itself is not a secure environment. Even if the network itself is secure (for example by using IPSec), there is no control as to who on the secure network is allowed to access and GET/SET (read/change/create/delete) the objects in this MIB. So even a locked-down network doesn't mean only the right people are poking at these objects. Not safe, not cute 💀
It is recommended that the implementors consider the security features as provided by the SNMPv3 framework. Specifically, the use of the User-based Security Model STD 62, RFC 3414 [RFC3414] and the View-based Access Control Model STD 62, RFC 3415 [RFC3415] is recommended. So go look at those two, they're the move 🔐
It is then a customer/user responsibility to ensure that the SNMP entity giving access to an instance of this MIB is properly configured to give access to only the objects, and those principals (users) that have legitimate rights to indeed GET or SET (change/create/delete) them. Basically, whoever runs it has to lock the door properly 🔑
10. Authors' Addresses 🦋
Andy Bierman Cisco Systems, Inc. 170 West Tasman Drive San Jose, CA USA 95134 Phone: +1 408-527-3711 EMail: abierman@cisco.com
Dan Romascanu Avaya Inc. Atidim Technology Park, Bldg. #3 Tel Aviv, 61131, Israel Phone: +972-3-545-8414 EMail: dromasca@avaya.com
K.C. Norseth L-3 Communications 640 N. 2200 West. Salt Lake City, Utah 84116-0850 Phone: +1 801-594-2809 EMail: kenyon.c.norseth@L-3com.com
11. Full Copyright Statement 🌈
Copyright (C) The Internet Society (2002). All Rights Reserved.
This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English.
The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement 🧚
Funding for the RFC Editor function is currently provided by the Internet Society. Thank you to them for keeping the RFC lights on ✨
📦 where this page comes from
- ietf: rfc3433 2002-12
- 💖 girlified by claude-haiku-5-5 on : a language model's rewrite of the original, under its terms