module ietf-alarms {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-alarms";
  prefix al;

  import ietf-yang-types {
    prefix yang;
    reference
      "RFC 6991: Common YANG Data Types.";
  }

  organization
    "IETF CCAMP Working Group";
  contact
    "WG Web:   <https://trac.ietf.org/trac/ccamp>
     WG List:  <mailto:ccamp@ietf.org>

     Editor:   Stefan Vallin
               <mailto:stefan@wallan.se>

     Editor:   Martin Bjorklund
               <mailto:mbj@tail-f.com>";
  description
    "This module defines an interface for managing alarms.  Main
     inputs to the module design are the 3GPP Alarm Integration
     Reference Point (IRP), ITU-T X.733, and ANSI/ISA-18.2 alarm
     standards.

     Main features of this module include:

       * Alarm list:
                 A list of all alarms.  Cleared alarms stay in
                 the list until explicitly purged.

       * Operator actions on alarms:
                 Acknowledging and closing alarms.

       * Administrative actions on alarms:
                 Purging alarms from the list according to specific
                 criteria.

       * Alarm inventory:
                 A management application can read all
                 alarm types implemented by the system.

       * Alarm shelving:
                 Shelving (blocking) alarms according
                 to specific criteria.

       * Alarm profiles:
                 A management system can attach further
                 information to alarm types, for example,
                 overriding system-default severity
                 levels.

     This module uses a stateful view on alarms.  An alarm is a state
     for a specific resource (note that an alarm is not a
     notification).  An alarm type is a possible alarm state for a
     resource.  For example, the tuple:

       ('link-alarm', 'GigabitEthernet0/25')

     is an alarm of type 'link-alarm' on the resource
     'GigabitEthernet0/25'.

     Alarm types are identified using YANG identities and an optional
     string-based qualifier.  The string-based qualifier allows for
     dynamic extension of the statically defined alarm types.  Alarm
     types identify a possible alarm state and not the individual
     notifications.  For example, the traditional 'link-down' and
     'link-up' notifications are two notifications referring to the
     same alarm type 'link-alarm'.

     With this design, there is no ambiguity about how alarm and
     alarm clear correlation should be performed; notifications that
     report the same resource and alarm type are considered updates
     of the same alarm, e.g., clearing an active alarm or changing
     the severity of an alarm.  The instrumentation can update the
     severity and alarm text on an existing alarm.  The above alarm
     example can therefore look like the following:

       (('link-alarm', 'GigabitEthernet0/25'),
        warning,
        'interface down while interface admin state is up')

     There is a clear separation between updates on the alarm from
     the underlying resource, like clear, and updates from an
     operator, like acknowledging or closing an alarm:

       (('link-alarm', 'GigabitEthernet0/25'),
        warning,
        'interface down while interface admin state is up',
        cleared,
        closed)

     Administrative actions like removing closed alarms older than a
     given time is supported.

     This YANG module does not define how the underlying
     instrumentation detects and clears the specific alarms.  That
     belongs to the Standards Development Organization (SDO) or
     enterprise that owns that specific technology.

     The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
     NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED',
     'MAY', and 'OPTIONAL' in this document are to be interpreted as
     described in BCP 14 (RFC 2119) (RFC 8174) when, and only when,
     they appear in all capitals, as shown here.

     Copyright (c) 2019 IETF Trust and the persons identified as
     authors of the code.  All rights reserved.

     Redistribution and use in source and binary forms, with or
     without modification, is permitted pursuant to, and subject to
     the license terms contained in, the Simplified BSD License set
     forth in Section 4.c of the IETF Trust's Legal Provisions
     Relating to IETF Documents
     (https://trustee.ietf.org/license-info).

     This version of this YANG module is part of RFC 8632; see
     the RFC itself for full legal notices.";

  revision 2019-09-11 {
    description
      "Initial revision.";
    reference
      "RFC 8632: A YANG Data Model for Alarm Management";
  }

  /*
   * Features
   */

  feature operator-actions {
    description
      "This feature indicates that the system supports operator
       states on alarms.";
  }

  feature alarm-shelving {
    description
      "This feature indicates that the system supports shelving
       (blocking) alarms.

       Alarm shelving may have an impact on server processing
       resources in order to match alarms against shelf
       criteria.";
  }

  feature alarm-history {
    description
      "This feature indicates that the server maintains a history
       of state changes for each alarm.  For example, if an alarm
       toggles between cleared and active 10 times, these state
       changes are present in a separate list in the alarm.

       Keeping the alarm history may have an impact on server
       memory resources.";
  }

  feature alarm-summary {
    description
      "This feature indicates that the server summarizes the number
       of alarms per severity and operator state.";
  }

  feature alarm-profile {
    description
      "The system enables clients to configure further information
       to each alarm type.";
  }

  feature severity-assignment {
    description
      "The system supports configurable alarm severity levels.";
    reference
      "ITU-T Recommendation M.3100:
         Generic network information model
       ITU-T Recommendation M.3160:
         Generic, protocol-neutral management information model";
  }

  feature root-cause-analysis {
    description
      "The system supports identifying candidate root-cause
       resources for an alarm, for example, a disk partition
       root cause for a logger failure alarm.";
  }

  feature service-impact-analysis {
    description
      "The system supports identifying candidate-impacted
       resources for an alarm, for example, an interface state change
       resulting in a link alarm, which can refer to a link as being
       impacted.";
  }

  feature alarm-correlation {
    description
      "The system supports correlating/grouping alarms
       that belong together.";
  }

  /*
   * Identities
   */

  identity alarm-type-id {
    description
      "Base identity for alarm types.  A unique identification of
       the alarm, not including the resource.  Different resources
       can share alarm types.  If the resource reports the same
       alarm type, it is considered to be the same alarm.  The alarm
       type is a simplification of the different X.733 and 3GPP Alarm
       IRP correlation mechanisms, and it allows for
       hierarchical extensions.

       A string-based qualifier can be used in addition to the
       identity in order to have different alarm types based on
       information not known at design time, such as values in
       textual SNMP Notification varbinds.

       Standards and vendors can define sub-identities to clearly
       identify specific alarm types.

       This identity is abstract and MUST NOT be used for alarms.";
  }

  /*
   * Common types
   */

  typedef resource {
    type union {
      type instance-identifier {
        require-instance false;
      }
      type yang:object-identifier;
      type string;
      type yang:uuid;
    }
    description
      "This is an identification of the alarming resource, such as an
       interface.  It should be as fine-grained as possible to both
       guide the operator and guarantee uniqueness of the alarms.

       If the alarming resource is modeled in YANG, this type will
       be an instance-identifier.

       If the resource is an SNMP object, the type will be an
       'object-identifier'.

       If the resource is anything else, for example, a distinguished
       name or a Common Information Model (CIM) path, this type will
       be a string.

       If the alarming object is identified by a Universally Unique
       Identifier (UUID), use the uuid type.  Be cautious when using
       this type, since a UUID is hard to use for an operator.

       If the server supports several models, the precedence should
       be in the order as given in the union definition.";
  }

  typedef resource-match {
    type union {
      type yang:xpath1.0;
      type yang:object-identifier;
      type string;
    }
    description
      "This type is used to match resources of type 'resource'.
       Since the type 'resource' is a union of different types, the
       'resource-match' type is also a union of corresponding types.

       If the type is given as an XPath 1.0 expression, a resource
       of type 'instance-identifier' matches if the instance is part
       of the node set that is the result of evaluating the XPath 1.0
       expression.  For example, the XPath 1.0 expression:

        /ietf-interfaces:interfaces/ietf-interfaces:interface
            [ietf-interfaces:type='ianaift:ethernetCsmacd']

       would match the resource instance-identifier:

        /if:interfaces/if:interface[if:name='eth1'],

       assuming that the interface 'eth1' is of type
       'ianaift:ethernetCsmacd'.

       If the type is given as an object identifier, a resource of
       type 'object-identifier' matches if the match object
       identifier is a prefix of the resource's object identifier.
       For example, the value:

        1.3.6.1.2.1.2.2

       would match the resource object identifier:

        1.3.6.1.2.1.2.2.1.1.5

       If the type is given as an UUID or a string, it is interpreted
       as an XML Schema regular expression, which matches a resource
       of type 'yang:uuid' or 'string' if the given regular
       expression matches the resource string.

       If the type is given as an XPath expression, it is evaluated
       in the following XPath context:

         o  The set of namespace declarations is the set of prefix
            and namespace pairs for all YANG modules implemented by
            the server, where the prefix is the YANG module name and
            the namespace is as defined by the 'namespace' statement
            in the YANG module.

            If a leaf of this type is encoded in XML, all namespace
            declarations in scope on the leaf element are added to
            the set of namespace declarations.  If a prefix found in
            the XML is already present in the set of namespace
            declarations, the namespace in the XML is used.

         o  The set of variable bindings is empty.

         o  The function library is the core function library, and
            the functions are defined in Section 10 of RFC 7950.

         o  The context node is the root node in the data tree.";
    reference
      "XML Schema Part 2: Datatypes Second Edition,
         World Wide Web Consortium Recommendation
         REC-xmlschema-2-20041028";
  }

  typedef alarm-text {
    type string;
    description
      "The string used to inform operators about the alarm.  This
       MUST contain enough information for an operator to be able to
       understand the problem and how to resolve it.  If this string
       contains structure, this format should be clearly documented
       for programs to be able to parse that information.";
  }

  typedef severity {
    type enumeration {
      enum indeterminate {
        value 2;
        description
          "Indicates that the severity level could not be
           determined.  This level SHOULD be avoided.";
      }
      enum warning {
        value 3;
        description
          "The 'warning' severity level indicates the detection of a
           potential or impending service-affecting fault, before any
           significant effects have been felt.  Action should be
           taken to further diagnose (if necessary) and correct the
           problem in order to prevent it from becoming a more
           serious service-affecting fault.";
      }
      enum minor {
        value 4;
        description
          "The 'minor' severity level indicates the existence of a
           non-service-affecting fault condition and that corrective
           action should be taken in order to prevent a more serious
           (for example, service-affecting) fault.  Such a severity
           can be reported, for example, when the detected alarm
           condition is not currently degrading the capacity of the
           resource.";
      }
      enum major {
        value 5;
        description
          "The 'major' severity level indicates that a service-
           affecting condition has developed and an urgent corrective
           action is required.  Such a severity can be reported, for
           example, when there is a severe degradation in the
           capability of the resource and its full capability must be
           restored.";
      }
      enum critical {
        value 6;
        description
          "The 'critical' severity level indicates that a service-
           affecting condition has occurred and an immediate
           corrective action is required.  Such a severity can be
           reported, for example, when a resource becomes totally out
           of service and its capability must be restored.";
      }
    }
    description
      "The severity level of the alarm.  Note well that the value
       'clear' is not included.  Whether or not an alarm is cleared
       is a separate boolean flag.";
    reference
      "ITU-T Recommendation X.733: Information Technology
         - Open Systems Interconnection
         - System Management: Alarm Reporting Function";
  }

  typedef severity-with-clear {
    type union {
      type enumeration {
        enum cleared {
          value 1;
          description
            "The alarm is cleared by the instrumentation.";
        }
      }
      type severity;
    }
    description
      "The severity level of the alarm including clear.  This is used
       only in notifications reporting state changes for an alarm.";
  }

  typedef writable-operator-state {
    type enumeration {
      enum none {
        value 1;
        description
          "The alarm is not being taken care of.";
      }
      enum ack {
        value 2;
        description
          "The alarm is being taken care of.  Corrective action not
           taken yet or has failed";
      }
      enum closed {
        value 3;
        description
          "Corrective action taken successfully.";
      }
    }
    description
      "Operator states on an alarm.  The 'closed' state indicates
       that an operator considers the alarm being resolved.  This is
       separate from the alarm's 'is-cleared' leaf.";
  }

  typedef operator-state {
    type union {
      type writable-operator-state;
      type enumeration {
        enum shelved {
          value 4;
          description
            "The alarm is shelved.  Alarms in /alarms/shelved-alarms/
             MUST be assigned this operator state by the server as
             the last entry in the 'operator-state-change' list.  The
             text for that entry SHOULD include the shelf name.";
        }
        enum un-shelved {
          value 5;
          description
            "The alarm is moved back to 'alarm-list' from a shelf.
             Alarms that are moved from /alarms/shelved-alarms/ to
             /alarms/alarm-list MUST be assigned this state by the
             server as the last entry in the 'operator-state-change'
             list.  The text for that entry SHOULD include the shelf
             name.";
        }
      }
    }
    description
      "Operator states on an alarm.  The 'closed' state indicates
       that an operator considers the alarm being resolved.  This is
       separate from the alarm's 'is-cleared' leaf.";
  }

  /* Alarm type */

  typedef alarm-type-id {
    type identityref {
      base alarm-type-id;
    }
    description
      "Identifies an alarm type.  The description of the alarm type
       id MUST indicate whether or not the alarm type is abstract.
       An abstract alarm type is used as a base for other alarm type
       ids and will not be used as a value for an alarm or be present
       in the alarm inventory.";
  }

  typedef alarm-type-qualifier {
    type string;
    description
      "If an alarm type cannot be fully specified at design time by
       'alarm-type-id', this string qualifier is used in addition to
       fully define a unique alarm type.

       The definition of alarm qualifiers is considered to be part of
       the instrumentation and is out of scope for this module.  An
       empty string is used when this is part of a key.";
  }

  /*
   * Groupings
   */

  grouping common-alarm-parameters {
    description
      "Common parameters for an alarm.

       This grouping is used both in the alarm list and in the
       notification representing an alarm-state change.";
    leaf resource {
      type resource;
      mandatory true;
      description
        "The alarming resource.  See also 'alt-resource'.  This could
         be, for example, a reference to the alarming interface";
    }
    leaf alarm-type-id {
      type alarm-type-id;
      mandatory true;
      description
        "This leaf and the leaf 'alarm-type-qualifier' together
         provide a unique identification of the alarm type.";
    }
    leaf alarm-type-qualifier {
      type alarm-type-qualifier;
      description
        "This leaf is used when the 'alarm-type-id' leaf cannot
         uniquely identify the alarm type.  Normally, this is not the
         case, and this leaf is the empty string.";
    }
    leaf-list alt-resource {
      type resource;
      description
        "Used if the alarming resource is available over other
         interfaces.  This field can contain SNMP OIDs, CIM paths, or
         3GPP distinguished names, for example.";
    }
    list related-alarm {
      if-feature "alarm-correlation";
      key "resource alarm-type-id alarm-type-qualifier";
      description
        "References to related alarms.  Note that the related alarm
         might have been purged from the alarm list.";
      leaf resource {
        type leafref {
          path "/alarms/alarm-list/alarm/resource";
          require-instance false;
        }
        description
          "The alarming resource for the related alarm.";
      }
      leaf alarm-type-id {
        type leafref {
          path "/alarms/alarm-list/alarm"
             + "[resource=current()/../resource]"
             + "/alarm-type-id";
          require-instance false;
        }
        description
          "The alarm type identifier for the related alarm.";
      }
      leaf alarm-type-qualifier {
        type leafref {
          path "/alarms/alarm-list/alarm"
             + "[resource=current()/../resource]"
             + "[alarm-type-id=current()/../alarm-type-id]"
             + "/alarm-type-qualifier";
          require-instance false;
        }
        description
          "The alarm qualifier for the related alarm.";
      }
    }
    leaf-list impacted-resource {
      if-feature "service-impact-analysis";
      type resource;
      description
        "Resources that might be affected by this alarm.  If the
         system creates an alarm on a resource and also has a mapping
         to other resources that might be impacted, these resources
         can be listed in this leaf-list.  In this way, the system
         can create one alarm instead of several.  For example, if an
         interface has an alarm, the 'impacted-resource' can
         reference the aggregated port channels.";
    }
    leaf-list root-cause-resource {
      if-feature "root-cause-analysis";
      type resource;
      description
        "Resources that are candidates for causing the alarm.  If the
         system has a mechanism to understand the candidate root
         causes of an alarm, this leaf-list can be used to list the
         root-cause candidate resources.  In this way, the system can
         create one alarm instead of several.  An example might be a
         logging system (alarm resource) that fails; the alarm can
         reference the file system in the 'root-cause-resource'
         leaf-list.  Note that the intended use is not to also send
         an alarm with the 'root-cause-resource' as an alarming
         resource.  The 'root-cause-resource' leaf-list is a hint and
         should not also generate an alarm for the same problem.";
    }
  }

  grouping alarm-state-change-parameters {
    description
      "Parameters for an alarm-state change.

       This grouping is used both in the alarm list's status-change
       list and in the notification representing an alarm-state
       change.";
    leaf time {
      type yang:date-and-time;
      mandatory true;
      description
        "The time the status of the alarm changed.  The value
         represents the time the real alarm-state change appeared in
         the resource and not when it was added to the alarm
         list.  The /alarm-list/alarm/last-changed MUST be set to the
         same value.";
    }
    leaf perceived-severity {
      type severity-with-clear;
      mandatory true;
      description
        "The severity of the alarm as defined by X.733.  Note that
         this may not be the original severity since the alarm may
         have changed severity.";
      reference
        "ITU-T Recommendation X.733: Information Technology
           - Open Systems Interconnection
           - System Management: Alarm Reporting Function";
    }
    leaf alarm-text {
      type alarm-text;
      mandatory true;
      description
        "A user-friendly text describing the alarm-state change.";
      reference
        "ITU-T Recommendation X.733: Information Technology
           - Open Systems Interconnection
           - System Management: Alarm Reporting Function";
    }
  }

  grouping operator-parameters {
    description
      "This grouping defines parameters that can be changed by an
       operator.";
    leaf time {
      type yang:date-and-time;
      mandatory true;
      description
        "Timestamp for operator action on the alarm.";
    }
    leaf operator {
      type string;
      mandatory true;
      description
        "The name of the operator that has acted on this alarm.";
    }
    leaf state {
      type operator-state;
      mandatory true;
      description
        "The operator's view of the alarm state.";
    }
    leaf text {
      type string;
      description
        "Additional optional textual information provided by the
         operator.";
    }
  }

  grouping resource-alarm-parameters {
    description
      "Alarm parameters that originate from the resource view.";
    leaf is-cleared {
      type boolean;
      mandatory true;
      description
        "Indicates the current clearance state of the alarm.  An
         alarm might toggle from active alarm to cleared alarm and
         back to active again.";
    }
    leaf last-raised {
      type yang:date-and-time;
      mandatory true;
      description
        "An alarm may change severity level and toggle between
         active and cleared during its lifetime.  This leaf indicates
         the last time it was raised ('is-cleared' = 'false').";
    }
    leaf last-changed {
      type yang:date-and-time;
      mandatory true;
      description
        "A timestamp when the 'status-change' or
         'operator-state-change' list was last changed.";
    }
    leaf perceived-severity {
      type severity;
      mandatory true;
      description
        "The last severity of the alarm.

         If an alarm was raised with severity 'warning' but later
         changed to 'major', this leaf will show 'major'.";
    }
    leaf alarm-text {
      type alarm-text;
      mandatory true;
      description
        "The last reported alarm text.  This text should contain
         information for an operator to be able to understand the
         problem and how to resolve it.";
    }
    list status-change {
      if-feature "alarm-history";
      key "time";
      min-elements 1;
      description
        "A list of status-change events for this alarm.

         The entry with latest timestamp in this list MUST
         correspond to the leafs 'is-cleared', 'perceived-severity',
         and 'alarm-text' for the alarm.

         This list is ordered according to the timestamps of alarm
         state changes.  The first item corresponds to the latest
         state change.

         The following state changes create an entry in this
         list:
         - changed severity (warning, minor, major, critical)
         - clearance status; this also updates the 'is-cleared'
           leaf
         - alarm-text update";
      uses alarm-state-change-parameters;
    }
  }

  grouping filter-input {
    description
      "Grouping to specify a filter construct on alarm information.";
    leaf alarm-clearance-status {
      type enumeration {
        enum any {
          description
            "Ignore alarm-clearance status.";
        }
        enum cleared {
          description
            "Filter cleared alarms.";
        }
        enum not-cleared {
          description
            "Filter not-cleared alarms.";
        }
      }
      mandatory true;
      description
        "The clearance status of the alarm.";
    }
    container older-than {
      presence "Age specification";
      description
        "Matches the 'last-status-change' leaf in the alarm.";
      choice age-spec {
        description
          "Filter using date and time age.";
        case seconds {
          leaf seconds {
            type uint16;
            description
              "Age expressed in seconds.";
          }
        }
        case minutes {
          leaf minutes {
            type uint16;
            description
              "Age expressed in minutes.";
          }
        }
        case hours {
          leaf hours {
            type uint16;
            description
              "Age expressed in hours.";
          }
        }
        case days {
          leaf days {
            type uint16;
            description
              "Age expressed in days.";
          }
        }
        case weeks {
          leaf weeks {
            type uint16;
            description
              "Age expressed in weeks.";
          }
        }
      }
    }
    container severity {
      presence "Severity filter";
      choice sev-spec {
        description
          "Filter based on severity level.";
        leaf below {
          type severity;
          description
            "Severity less than this leaf.";
        }
        leaf is {
          type severity;
          description
            "Severity level equal to this leaf.";
        }
        leaf above {
          type severity;
          description
            "Severity level higher than this leaf.";
        }
      }
      description
        "Filter based on severity.";
    }
    container operator-state-filter {
      if-feature "operator-actions";
      presence "Operator state filter";
      leaf state {
        type operator-state;
        description
          "Filter on operator state.";
      }
      leaf user {
        type string;
        description
          "Filter based on which operator.";
      }
      description
        "Filter based on operator state.";
    }
  }

  /*
   * The /alarms data tree
   */

  container alarms {
    description
      "The top container for this module.";
    container control {
      description
        "Configuration to control the alarm behavior.";
      leaf max-alarm-status-changes {
        type union {
          type uint16;
          type enumeration {
            enum infinite {
              description
                "The status-change entries are accumulated
                 infinitely.";
            }
          }
        }
        default "32";
        description
          "The 'status-change' entries are kept in a circular list
           per alarm.  When this number is exceeded, the oldest
           status change entry is automatically removed.  If the
           value is 'infinite', the status-change entries are
           accumulated infinitely.";
      }
      leaf notify-status-changes {
        type enumeration {
          enum all-state-changes {
            description
              "Send notifications for all status changes.";
          }
          enum raise-and-clear {
            description
              "Send notifications only for raise, clear, and
               re-raise.  Notifications for severity-level changes or
               alarm-text changes are not sent.";
          }
          enum severity-level {
            description
              "Only send notifications for alarm-state changes
               crossing the level specified in
               'notify-severity-level'.  Always send clear
               notifications.";
          }
        }
        must '. != "severity-level" or ../notify-severity-level' {
          description
            "When notify-status-changes is 'severity-level', a value
             must be given for 'notify-severity-level'.";
        }
        default "all-state-changes";
        description
          "This leaf controls the notifications sent for alarm status
           updates.  There are three options:

           1.  Notifications are sent for all updates, severity-level
               changes, and alarm-text changes.

           2.  Notifications are only sent for alarm raise and clear.

           3.  Notifications are sent for status changes equal to or
               above the specified severity level.  Clear
               notifications shall always be sent.  Notifications
               shall also be sent for state changes that make an
               alarm less severe than the specified level.

           For example, in option 3, assume that the severity level
           is set to major and that the alarm has the following state
           changes:

           [(Time, severity, clear)]:
           [(T1, major, -), (T2, minor, -), (T3, warning, -),
            (T4, minor, -), (T5, major, -), (T6, critical, -),
            (T7, major.  -), (T8, major, clear)]

           In that case, notifications will be sent at times
           T1, T2, T5, T6, T7, and T8.";
      }
      leaf notify-severity-level {
        when '../notify-status-changes = "severity-level"';
        type severity;
        description
          "Only send notifications for alarm-state changes crossing
           the specified level.  Always send clear notifications.";
      }
      container alarm-shelving {
        if-feature "alarm-shelving";
        description
          "The 'alarm-shelving/shelf' list is used to shelve
           (block/filter) alarms.  The conditions in the shelf
           criteria are logically ANDed.  The first matching shelf is
           used, and an alarm is shelved only for this first match.
           Matching alarms MUST appear in the
           /alarms/shelved-alarms/shelved-alarm list, and
           non-matching /alarms MUST appear in the
           /alarms/alarm-list/alarm list.  The server does not send
           any notifications for shelved alarms.

           The server MUST maintain states (e.g., severity
           changes) for the shelved alarms.

           Alarms that match the criteria shall have an
           operator state 'shelved'.  When the shelf
           configuration removes an alarm from the shelf, the server
           shall add the operator state 'un-shelved'.";
        list shelf {
          key "name";
          ordered-by user;
          leaf name {
            type string;
            description
              "An arbitrary name for the alarm shelf.";
          }
          description
            "Each entry defines the criteria for shelving alarms.
             Criteria are ANDed.  If no criteria are specified,
             all alarms will be shelved.";
          leaf-list resource {
            type resource-match;
            description
              "Shelve alarms for matching resources.";
          }
          list alarm-type {
            key "alarm-type-id alarm-type-qualifier-match";
            description
              "Any alarm matching the combined criteria of
               'alarm-type-id' and 'alarm-type-qualifier-match'
               MUST be matched.";
            leaf alarm-type-id {
              type alarm-type-id;
              description
                "Shelve all alarms that have an 'alarm-type-id' that
                 is equal to or derived from the given
                 'alarm-type-id'.";
            }
            leaf alarm-type-qualifier-match {
              type string;
              description
                "An XML Schema regular expression that is used to
                 match an alarm type qualifier.  Shelve all alarms
                 that match this regular expression for the alarm
                 type qualifier.";
              reference
                "XML Schema Part 2: Datatypes Second Edition,
                   World Wide Web Consortium Recommendation
                   REC-xmlschema-2-20041028";
            }
          }
          leaf description {
            type string;
            description
              "An optional textual description of the shelf.  This
               description should include the reason for shelving
               these alarms.";
          }
        }
      }
    }
    container alarm-inventory {
      config false;
      description
        "The 'alarm-inventory/alarm-type' list contains all possible
         alarm types for the system.

         If the system knows for which resources a specific alarm
         type can appear, it is also identified in the inventory.
         The list also tells if each alarm type has a corresponding
         clear state.  The inventory shall only contain concrete
         alarm types.

         The alarm inventory MUST be updated by the system when new
         alarms can appear.  This can be the case when installing new
         software modules or inserting new card types.  A
         notification 'alarm-inventory-changed' is sent when the
         inventory is changed.";
      list alarm-type {
        key "alarm-type-id alarm-type-qualifier";
        description
          "An entry in this list defines a possible alarm.";
        leaf alarm-type-id {
          type alarm-type-id;
          description
            "The statically defined alarm type identifier for this
             possible alarm.";
        }
        leaf alarm-type-qualifier {
          type alarm-type-qualifier;
          description
            "The optionally dynamically defined alarm type identifier
             for this possible alarm.";
        }
        leaf-list resource {
          type resource-match;
          description
            "Optionally, specifies for which resources the alarm type
             is valid.";
        }
        leaf will-clear {
          type boolean;
          mandatory true;
          description
            "This leaf tells the operator if the alarm will be
             cleared when the correct corrective action has been
             taken.  Implementations SHOULD strive for detecting the
             cleared state for all alarm types.

             If this leaf is 'true', the operator can monitor the
             alarm until it becomes cleared after the corrective
             action has been taken.

             If this leaf is 'false', the operator needs to validate
             that the alarm is no longer active using other
             mechanisms.  Alarms can lack a corresponding clear due
             to missing instrumentation or no logical
             corresponding clear state.";
        }
        leaf-list severity-level {
          type severity;
          description
            "This leaf-list indicates the possible severity levels of
             this alarm type.  Note well that 'clear' is not part of
             the severity type.  In general, the severity level
             should be defined by the instrumentation based on the
             dynamic state, rather than being defined statically by
             the alarm type, in order to provide a relevant severity
             level based on dynamic state and context.  However, most
             alarm types have a defined set of possible severity
             levels, and this should be provided here.";
        }
        leaf description {
          type string;
          mandatory true;
          description
            "A description of the possible alarm.  It SHOULD include
             information on possible underlying root causes and
             corrective actions.";
        }
      }
    }
    container summary {
      if-feature "alarm-summary";
      config false;
      description
        "This container gives a summary of the number of alarms.";
      list alarm-summary {
        key "severity";
        description
          "A global summary of all alarms in the system.  The summary
           does not include shelved alarms.";
        leaf severity {
          type severity;
          description
            "Alarm summary for this severity level.";
        }
        leaf total {
          type yang:gauge32;
          description
            "Total number of alarms of this severity level.";
        }
        leaf not-cleared {
          type yang:gauge32;
          description
            "Total number of alarms of this severity level
             that are not cleared.";
        }
        leaf cleared {
          type yang:gauge32;
          description
            "For this severity level, the number of alarms that are
             cleared.";
        }
        leaf cleared-not-closed {
          if-feature "operator-actions";
          type yang:gauge32;
          description
            "For this severity level, the number of alarms that are
             cleared but not closed.";
        }
        leaf cleared-closed {
          if-feature "operator-actions";
          type yang:gauge32;
          description
            "For this severity level, the number of alarms that are
             cleared and closed.";
        }
        leaf not-cleared-closed {
          if-feature "operator-actions";
          type yang:gauge32;
          description
            "For this severity level, the number of alarms that are
             not cleared but closed.";
        }
        leaf not-cleared-not-closed {
          if-feature "operator-actions";
          type yang:gauge32;
          description
            "For this severity level, the number of alarms that are
             not cleared and not closed.";
        }
      }
      leaf shelves-active {
        if-feature "alarm-shelving";
        type empty;
        description
          "This is a hint to the operator that there are active
           alarm shelves.  This leaf MUST exist if the
           /alarms/shelved-alarms/number-of-shelved-alarms is > 0.";
      }
    }
    container alarm-list {
      config false;
      description
        "The alarms in the system.";
      leaf number-of-alarms {
        type yang:gauge32;
        description
          "This object shows the total number of
           alarms in the system, i.e., the total number
           of entries in the alarm list.";
      }
      leaf last-changed {
        type yang:date-and-time;
        description
          "A timestamp when the alarm list was last
           changed.  The value can be used by a manager to
           initiate an alarm resynchronization procedure.";
      }
      list alarm {
        key "resource alarm-type-id alarm-type-qualifier";
        description
          "The list of alarms.  Each entry in the list holds one
           alarm for a given alarm type and resource.  An alarm can
           be updated from the underlying resource or by the user.
           The following leafs are maintained by the resource:
           'is-cleared', 'last-change', 'perceived-severity', and
           'alarm-text'.  An operator can change 'operator-state' and
           'operator-text'.

           Entries appear in the alarm list the first time an alarm
           becomes active for a given alarm type and resource.
           Entries do not get deleted when the alarm is cleared.
           Clear status is represented as a boolean flag.

           Alarm entries are removed, i.e., purged, from the list by
           an explicit purge action.  For example, purge all alarms
           that are cleared and in closed operator state that are
           older than 24 hours.  Purged alarms are removed from the
           alarm list.  If the alarm resource state changes after a
           purge, the alarm will reappear in the alarm list.

           Systems may also remove alarms based on locally configured
           policies; this is out of scope for this module.";
        uses common-alarm-parameters;
        leaf time-created {
          type yang:date-and-time;
          mandatory true;
          description
            "The timestamp when this alarm entry was created.  This
             represents the first time the alarm appeared; it can
             also represent that the alarm reappeared after a purge.
             Further state changes of the same alarm do not change
             this leaf; these changes will update the 'last-changed'
             leaf.";
        }
        uses resource-alarm-parameters;
        list operator-state-change {
          if-feature "operator-actions";
          key "time";
          description
            "This list is used by operators to indicate the state of
             human intervention on an alarm.  For example, if an
             operator has seen an alarm, the operator can add a new
             item to this list indicating that the alarm is
             acknowledged.";
          uses operator-parameters;
        }
        action set-operator-state {
          if-feature "operator-actions";
          description
            "This is a means for the operator to indicate the level
             of human intervention on an alarm.";
          input {
            leaf state {
              type writable-operator-state;
              mandatory true;
              description
                "Set this operator state.";
            }
            leaf text {
              type string;
              description
                "Additional optional textual information.";
            }
          }
        }
        notification operator-action {
          if-feature "operator-actions";
          description
            "This notification is used to report that an operator
             acted upon an alarm.";
          uses operator-parameters;
        }
      }
      action purge-alarms {
        description
          "This operation requests that the server delete entries
           from the alarm list according to the supplied criteria.

           Typically, this operation is used to delete alarms that
           are in closed operator state and older than a specified
           time.

           The number of purged alarms is returned as an output
           parameter.";
        input {
          uses filter-input;
        }
        output {
          leaf purged-alarms {
            type uint32;
            description
              "Number of purged alarms.";
          }
        }
      }
      action compress-alarms {
        if-feature "alarm-history";
        description
          "This operation requests that the server compress
           entries in the alarm list by removing all but the
           latest 'status-change' entry for all matching alarms.
           Conditions in the input are logically ANDed.  If no
           input condition is given, all alarms are compressed.";
        input {
          leaf resource {
            type resource-match;
            description
              "Compress the alarms matching this resource.";
          }
          leaf alarm-type-id {
            type leafref {
              path "/alarms/alarm-list/alarm/alarm-type-id";
              require-instance false;
            }
            description
              "Compress alarms with this 'alarm-type-id'.";
          }
          leaf alarm-type-qualifier {
            type leafref {
              path "/alarms/alarm-list/alarm/alarm-type-qualifier";
              require-instance false;
            }
            description
              "Compress the alarms with this
               'alarm-type-qualifier'.";
          }
        }
        output {
          leaf compressed-alarms {
            type uint32;
            description
              "Number of compressed alarm entries.";
          }
        }
      }
    }
    container shelved-alarms {
      if-feature "alarm-shelving";
      config false;
      description
        "The shelved alarms.  Alarms appear here if they match the
         criteria in /alarms/control/alarm-shelving.  This list does
         not generate any notifications.  The list represents alarms
         that are considered not relevant by the operator.  Alarms in
         this list have an 'operator-state' of 'shelved'.  This
         cannot be changed.";
      leaf number-of-shelved-alarms {
        type yang:gauge32;
        description
          "This object shows the total number of current
           alarms, i.e., the total number of entries
           in the alarm list.";
      }
      leaf shelved-alarms-last-changed {
        type yang:date-and-time;
        description
          "A timestamp when the shelved-alarm list was last changed.
           The value can be used by a manager to initiate an alarm
           resynchronization procedure.";
      }
      list shelved-alarm {
        key "resource alarm-type-id alarm-type-qualifier";
        description
          "The list of shelved alarms.  Shelved alarms can only be
           updated from the underlying resource; no operator actions
           are supported.";
        uses common-alarm-parameters;
        leaf shelf-name {
          type leafref {
            path "/alarms/control/alarm-shelving/shelf/name";
            require-instance false;
          }
          description
            "The name of the shelf.";
        }
        uses resource-alarm-parameters;
        list operator-state-change {
          if-feature "operator-actions";
          key "time";
          description
            "This list is used by operators to indicate the state of
             human intervention on an alarm.  For shelved alarms, the
             system has set the list item in the list to 'shelved'.";
          uses operator-parameters;
        }
      }
      action purge-shelved-alarms {
        description
          "This operation requests that the server delete entries from
           the shelved-alarm list according to the supplied criteria.
           In the shelved-alarm list, it makes sense to delete alarms
           that are not relevant anymore.

           The number of purged alarms is returned as an output
           parameter.";
        input {
          uses filter-input;
        }
        output {
          leaf purged-alarms {
            type uint32;
            description
              "Number of purged alarms.";
          }
        }
      }
      action compress-shelved-alarms {
        if-feature "alarm-history";
        description
          "This operation requests that the server compress entries
           in the shelved-alarm list by removing all but the latest
           'status-change' entry for all matching shelved alarms.
           Conditions in the input are logically ANDed.  If no input
           condition is given, all alarms are compressed.";
        input {
          leaf resource {
            type leafref {
              path "/alarms/shelved-alarms/shelved-alarm/resource";
              require-instance false;
            }
            description
              "Compress the alarms with this resource.";
          }
          leaf alarm-type-id {
            type leafref {
              path "/alarms/shelved-alarms/shelved-alarm"
                 + "/alarm-type-id";
              require-instance false;
            }
            description
              "Compress alarms with this 'alarm-type-id'.";
          }
          leaf alarm-type-qualifier {
            type leafref {
              path "/alarms/shelved-alarms/shelved-alarm"
                 + "/alarm-type-qualifier";
              require-instance false;
            }
            description
              "Compress the alarms with this
               'alarm-type-qualifier'.";
          }
        }
        output {
          leaf compressed-alarms {
            type uint32;
            description
              "Number of compressed alarm entries.";
          }
        }
      }
    }
    list alarm-profile {
      if-feature "alarm-profile";
      key "alarm-type-id alarm-type-qualifier-match resource";
      ordered-by user;
      description
        "This list is used to assign further information or
         configuration for each alarm type.  This module supports a
         mechanism where the client can override the system-default
         alarm severity levels.  The 'alarm-profile' is also a useful
         augmentation point for specific additions to alarm types.";
      leaf alarm-type-id {
        type alarm-type-id;
        description
          "The alarm type identifier to match.";
      }
      leaf alarm-type-qualifier-match {
        type string;
        description
          "An XML Schema regular expression that is used to match the
           alarm type qualifier.";
        reference
          "XML Schema Part 2: Datatypes Second Edition,
             World Wide Web Consortium Recommendation
             REC-xmlschema-2-20041028";
      }
      leaf resource {
        type resource-match;
        description
          "Specifies which resources to match.";
      }
      leaf description {
        type string;
        mandatory true;
        description
          "A description of the alarm profile.";
      }
      container alarm-severity-assignment-profile {
        if-feature "severity-assignment";
        description
          "The client can override the system-default severity
           level.";
        reference
          "ITU-T Recommendation M.3100:
             Generic network information model
           ITU-T Recommendation M.3160:
             Generic, protocol-neutral management information model";
        leaf-list severity-level {
          type severity;
          ordered-by user;
          description
            "Specifies the configured severity level(s) for the
             matching alarm.  If the alarm has several severity
             levels, the leaf-list shall be given in rising severity
             order.  The original M3100/M3160 ASAP function only
             allows for a one-to-one mapping between alarm type and
             severity, but since YANG module supports stateful
             alarms, the mapping must allow for several severity
             levels.

             Assume a high-utilization alarm type with two thresholds
             with the system-default severity levels of threshold1 =
             warning and threshold2 = minor.  Setting this leaf-list
             to (minor, major) will assign the severity levels as
             threshold1 = minor and threshold2 = major";
        }
      }
    }
  }

  /*
   * Notifications
   */

  notification alarm-notification {
    description
      "This notification is used to report a state change for an
       alarm.  The same notification is used for reporting a newly
       raised alarm, a cleared alarm, or changing the text and/or
       severity of an existing alarm.";
    uses common-alarm-parameters;
    uses alarm-state-change-parameters;
  }

  notification alarm-inventory-changed {
    description
      "This notification is used to report that the list of possible
       alarms has changed.  This can happen when, for example, a new
       software module is installed or a new physical card is
       inserted.";
  }
}