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Version: 8.1

Tag Properties

Tags are points of data and may have static values or dynamic values that come from an OPC address, an Expression, or a SQL query. The values can be used on screens and in Transaction Groups. Additionally, Tags offer a core set of features above and beyond simple values, such as scaling, alarming, and history logging. Depending on the specific type of tag, even more options are available. In general, Tags provide a common interface for tying together many types of data in Ignition.

Changed in 8.1.17
In 8.1.17, the Tag Editor was redesigned to improve usability. The new Tag Editor now requires fewer clicks and keeps relevant tag information visible while modifying bindings, alarms, and event scripts. Pages detailing features of the previous Tag Editor can be found in Deprecated Ignition Features.

Tag Configuration in the Designer

Tags are managed in the Tag Editor. To configure a Tag, right-click on it and select Edit Tag. Or create a new Tag by right-clicking on the Tags folder in the Tag Browser and use the New Tag option to select a new Tag type.

Once the Tag Editor window is displayed you can set the properties for that Tag. The Tag Editor window has the following sections depending on the type of Tag you are creating:

  • Basic Properties
  • Value
  • Numeric Properties
  • Meta Data Properties
  • Security
  • Scripting
  • Alarms
  • History

Tag Object Types

Some features, such as system.tag.browse, can access the Object Type of the tag (sometimes called "tagType"). Below is a table representing the possible types.

Tag ObjectDescription
PropertyA single value underneath an node.
NodeAn entity that may have a value and may have children. "Node" is a generic term for other objects in this table, such as a Folder or AtomicTag.
FolderRepresented by a folder in the Tag Browser. Folders generally have child nodes, but don't have values or other properties that make up a tag.
AtomicTagA "normal" type of tag. Objects with this type can be one of the following (based on the Value Source property):
  • OPC Tag
  • Query Tag
  • Expression Tag
  • Derived Tag
  • Reference Tag
  • Memory Tag
UdtInstanceAn instance of a complex tag instance (UDT Instance). It's important to note that UdtInstances contain other nodes, so this type is generally only seen at the root of a UDT instance.
Thus, nodes under a UdtInstance are not considered to have a type of "UdtInstance", unless the child node is actually a UdtInstance: in other words, a nested UDT instance.
UdtTypeRepresents the root of a complex tag definition (UDT Definition). Similar to UdtInstance, nodes under a UdtType have their own object type, so a UdtType represents the root of a complex tag.
ProviderRepresents a Tag Provider.

Standard Tag Properties Table

This following table provides detail on each Tag Property, including the binding name, description, data type, and the Tag Types that use the property.

Basic Properties

PropertyJSON/Scripting NameDescriptionData TypeApplicable Tag Type
NamenameHow the Tag will be presented and referenced in the system. The Tag path will be the provider, the folder structure, and this name.StringOPC, Query, Expression, Derived, Client, Reference, Memory
Tag GrouptagGroupThe Tag Group that will execute the Tag. The Tag Group dictates the rate and conditions on which the Tag will be evaluated. For more details, see Tag Groups.StringOPC, Query, Expression, Derived, Reference, Memory
EnabledenabledWhether the Tag will be evaluated by the Tag Group. If false, the Tag will still be present, but will have a bad quality.BooleanOPC, Query, Expression, Derived, Reference, Memory

Value Properties

PropertyJSON/Scripting NameDescriptionData TypeApplicable Tag Type
Tag Type (unlisted)tagTypeThe type of the node. See the Tag Object Types table for more information.
Note: This property does not appear in the Tag Editor, but is accessible via scripting.
StringOPC, Query, Expression, Derived, Reference, Memory
Type ID (unlisted)typeIdReturns a path representing which UDT this node is derived from. If the node is not a UDT, then this property will return a None object.
Note: This property does not appear in the Tag Editor, but is accessible via scripting.
StringOPC, Query, Expression, Derived, Reference, Memory
Value SourcevalueSourceSpecifies how the Tag determines its value. In other words, sets the type of the Tag (Memory, OPC, Expression, etc). Below is a list of possible values and their JSON representation:
  • Derived - derived
  • Expression - expr
  • Memory - memory
  • OPC - opc
  • Query - db
  • Reference - reference
StringOPC, Query, Expression, Derived, Reference, Memory
Data TypedataTypeThe data type of the Tag. It is important that this be set as correctly as possible with regards to the Tag's underlying data source. The Tag system will attempt to coerce any raw incoming value (for example, from OPC or a SQL query) into the desired type. For detailed information and a list of possible values, see Tag Data Types.
Note: Regarding Array data types, Alarming, Scaling, and Historical settings applied to an array Tag are propagated down to elements in the array.
StringOPC, Query, Expression, Derived, Reference, Memory
ValuevalueThe value of the Tag. Can only be modified if the Tag allows value writing and the user has sufficient privileges.Object (depends on the data type of the Tag)Memory
OPC ServeropcServerOnly present for OPC Tags. The server against which to subscribe the data point. Only present for OPC Tags.StringOPC
OPC Item PathopcItemPathOnly present for OPC Tags. The path to subscribe to on the server. The point will be subscribed at the rate dictated by the Tag Group.
New in 8.1.5
It's possible to escape curly braces {} in the item path by using additional curly braces. For example:
{{device_name}} would evaluate to {<device_name value>}, allowing you to include braces in the Item Path.
StringOPC
Source Tag PathsourceTagPathThe path to the Tag that this Tag is referencing. Only present for Reference and Derived Tags.StringDerived, Reference
Execution ModeexecutionModeDetermines how and when the Tag executes. Possible values are listed below along with JSON names and descriptions:

  • Event Driven EventDriven : Updates when something happens (i.e., value event or alarm event) within the expression.
  • Fixed Rate FixedRate : Tag will be executed at the set or fixed rate. Adds the Execution Rate property, which determines how often the Tag executes in milliseconds.
  • Tag Group TagGroupRate : Tags are executed by Tag Groups, which dictate the rate of execution.
StringExpression, Query
ExpressionexpressionThe expression the Tag will use to determine its value.StringExpression
Read ExpressionderiveExpressionGetterThe expression that determines how the value on the Derived Tag is displayed.StringDerived
QueryqueryThe SQL query to be run, which drives the tag's value. Queries doing database reads and writes are possible, see the Query Type property description for details.StringQuery
Write ExpressionderiveExpressionSetterThe expression that determines how the value on the Derived Tag is displayed.StringDerived
DatasourcedatasourceThe database connection that the query Tag will execute against.StringQuery
Query TypequeryType
New in 8.1.3
Defines whether the query is executing a database read or a database write. Important for determining the value behavior of the Tag.Possible values are:
  • AutoDetect - Query type is determined from the query itself.
  • Select - Dictates that the query is reading data from the database. The query result set will be stored on the Tag's value.
  • Update - Dictates that the query is writing data to the database (but does not require an UPDATE statement in the query, specifically). The value on the query Tag will be the number of affected rows.
StringQuery

Numeric Properties

PropertyJSON/Scripting NameDescriptionData TypeApplicable Tag Type
DeadbanddeadbandA numerical value used to prevent unnecessary updates for Tags whose values change by small amounts.NumericOPC, Query, Expression, Derived, Reference, Memory
Deadband ModedeadbandModeDefines how the deadband value is used. Possible values along with JSON names and descriptions are listed below:

  • Absolute Absolute : The deadband setting is considered to be an absolute value.
  • Percent Percent : The actual deadband is calculated as a percent of the Tag's engineering unit span.
  • Off Off :
    New in 8.1.2
    The deadband setting is the equivalent to a value of 0.0, so that all values pass through if their timestamp has changed.
StringOPC, Query, Expression, Derived, Reference, Memory
Scale ModescaleModeIf and how the Tag value will be scaled between the source, and what is reported for the Tag. A listing of possible values along with their JSON names and numerical representation can be found below:

  • Off Off: 0
  • Linear Linear: 1
  • Square Root SquareRoot: 2
  • Exponential Filter ExponentialFilter: 3
  • Bit Inversion BitInversion: 4
StringOPC, Query, Expression, Derived, Reference, Memory
Raw LowrawLowStart of the "raw" value range. Only present if Scale Mode is set to Linear or Square Root.NumericOPC, Query, Expression, Derived, Reference, Memory
Raw HighrawHighEnd of the "raw" value range. Only present if Scale Mode is set to Linear or Square Root.NumericOPC, Query, Expression, Derived, Reference, Memory
Scaled LowscaledLowStart of "scaled" value range. Raw low will map to Scaled low for the Tag. Only present if Scale Mode is set to Linear or Square Root.NumericOPC, Query, Expression, Derived, Reference, Memory
Scaled HighscaledHighEnd of "scaled" value range. Raw high will map to Scaled high for the Tag. Only present if Scale Mode is set to Linear or Square Root.NumericOPC, Query, Expression, Derived, Reference, Memory
Clamp ModeclampModeHow values that fall outside of the ranges will be treated. "Clamped" values will be adjusted to the low/high scaled value as appropriate. Only present if Scale Mode is set to Linear or Square Root. Possible values along with their JSON names and numerical representation are listed below:

  • No_Clamp No_Clamp : 0
  • Clamp_Low Clamp_Low : 1
  • Clamp_High Clamp_High : 2
  • Clamp_Both Clamp_Both : 3
StringOPC, Query, Expression, Derived, Reference, Memory
Scale FactorscaleFactorFor single parameter modes (currently only Exponential Filter), the factor parameter for the equation. Used when the Scale Mode property is set to Exponential FilterNumericOPC, Query, Expression, Derived, Reference, Memory
Engineering UnitsengUnitThe engineering units of the value.StringOPC, Query, Expression, Derived, Reference, Memory
Engineering Low LimitengLowThe lowest expected value of the Tag.NumericOPC, Query, Expression, Derived, Reference, Memory
Engineering High LimitengHighThe highest expected value of the Tag.NumericOPC, Query, Expression, Derived, Reference, Memory
Engineering Limit ModeengLimitModeDictates how the engineering range should be enforced on the Tag. If not "Off", the Tag will change to bad quality ("limit exceeded"), when the value falls outside the specified range. Possible values along with their JSON names and numerical representations are listed below:

  • No_Clamp No_Clamp : 0
  • Clamp_Low Clamp_Low : 1
  • Clamp_High Clamp_High : 2
  • Clamp_Both Clamp_Both : 3
NumericOPC, Query, Expression, Derived, Reference, Memory
Format StringformatStringHow the value should be formatted when converted to a string (only applies to numerical data types). Uses # and 0 characters to describe the format.
  • # - If the number in this position is non-zero, then do not show the position. Otherwise, show the number. Useful when you only want to show a decimal position if the value is non-zero.
  • 0 - If the number in this position is non-zero, then show that number. Otherwise, show a zero. Useful to add leading and trailing zeros to a value.

See Data Type Formatting Reference.
StringOPC, Query, Expression, Derived, Reference, Memory

Meta Data Properties

PropertyJSON/Scripting NameDescriptionData TypeApplicable Tag Type
TooltiptooltipThe tooltip provides a hint to visual components as to what should be displayed when the user hovers their mouse cursor over the component that is being driven by the value of this Tag.

New in 8.1.18
Hovering over the Tag itself in the Tag Browser will also display this hint.
StringOPC, Query, Expression, Derived, Reference, Memory
DocumentationdocumentationA freeform text property for information about the Tag.StringOPC, Query, Expression, Derived, Reference, Memory

Security Data Properties

PropertyJSON/Scripting NameDescriptionData TypeApplicable Tag Type
Read PermissionsreadPermissionsDefines the security levels required in order to read values from a Tag. For more information, see Tag Security Properties. See the Permission Values section for a description of possible values.JSON ObjectOPC, Query, Expression, Derived, Reference, Memory
Read OnlyreadOnlyDefines whether a Tag is read-only or writeable. For more information, see Tag Security Properties.BooleanOPC, Query, Expression, Derived, Reference, Memory
Write PermissionswritePermissionsDefines the security levels required in order to read values from a Tag. For more information, see Tag Security Properties. See the Permission Values section for a description of possible values.JSON ObjectOPC, Query, Expression, Derived, Reference, Memory

Permission Values

ModeJSON/Scripting NameDescription
TypetypeRepresents the selected radio button on the security level UI, determining if all of the elements in the securityLevels array are required, or if any of the elements are allowed. Possible values are:
  • AnyOf
  • AllOf
Security LevelssecurityLevelsRepresents allowed security levels for this permission. Each level is represented as a JSON object, containing a "name" value that represents the name of a security level, and a "children" array which represents any levels under the current. The actual "selected" levels are any levels that have an empty "children" object. See the example below for more information.

JSON Example

The JSON in this example uses the configuration shown in the image below. Permission is granted if the security levels on the request are from either an "Administrator" user, or if the request originated from the "Zone A" Security Zone.

"readPermissions": {
"type": "AnyOf",
"securityLevels": [
{
"name": "Authenticated",
"children": [
{
"name": "Roles",
"children": [
{
"name": "Administrator",
"children": []
}
]
}
]
},
{
"name": "SecurityZones",
"children": [
{
"name": "Zone A",
"children": []
}
]
}
]
}

Scripting Properties

PropertyJSON/Scripting NameDescriptionData TypeApplicable Tag Type
Tag Event ScriptseventScriptsEach Tag has the option to have Tag Event Scripts on it. When you edit a Tag, you can navigate to the Tag Events screen to see a list of all of the Tag scripts. You can then select which event you would like to write a script for. You can even write a script for multiple events if you like. For detailed information, see Tag Event Scripts.
When interacting with a Tag from a script, the Tag Event Scripts are represented as an array of JSON objects. Each JSON object is described below in the Key Description section.
JSON ArrayOPC, Query, Expression, Derived, Reference, Memory

Key Description

KeyDescription
eventidA value representing the type of event script. See values below for a list of possible events.
  • Quality Changed: qualityChanged
  • Value Changed: valueChanged
  • Alarm Active: alarmActive
  • Alarm Cleared: alarmCleared
  • Alarm Acknowledged: alarmAcked
  • scriptA value representing the content of the script

    Alarms Properties

    PropertyJSON/Scripting NameDescriptionData TypeApplicable Tag Type
    AlarmsalarmsTags have the ability to define any number of alarms. Each alarm is a condition that will be evaluated when the value of the Tag changes. When the condition becomes true, the alarm is said to be active. When it becomes false, the alarm is said to be cleared.
    For detailed information, see Tag Alarm Properties.
    JSON Array of JSON objects. For detailed information, see Tag Alarm Properties .OPC, Query, Expression, Derived, Reference, Memory
    Alarm Eval EnabledalarmEvalEnabledDetermines if alarms will be evaluated on this tag.BooleanOPC, Query, Expression, Derived, Reference, Memory

    History Properties

    PropertyJSON/Scripting NameDescriptionData TypeApplicable Tag Type
    History EnabledhistoryEnabledWhether the Tag will report its history to the Tags Historian system.BooleanOPC, Query, Expression, Derived, Reference, Memory
    Storage ProviderhistoryProviderWhich Tag Historian data store the Tag will target. A particular Tag can only target one history store. For more information, refer to History Providers on the Tag History Gateway Settings page.
    Note: The Storage Provider dropdown displays the provider names as they are written at the time of tag configuration. If the Storage Provider name is updated later, this setting will need to be adjusted to match the new Storage Provider name.
    StringOPC, Query, Expression, Derived, Reference, Memory
    Deadband StylehistoricalDeadbandStyleThere are three styles to choose from: Auto, Analog, or Discrete.
    When set to Auto, this setting will automatically pick from Analog or Discrete, based on the data type of the Tag.
    • If the data type of the Tag is set to a float or double, then Auto will use the Analog Style
    • If the data type of the Tag is any other type, then the Discrete style will be used.


    More information on the Analog and Discrete types can be found on the Configuring Tag History page.

    A list of possible values along with their JSON name can be found below:

    • Auto Auto
    • Analog Analog_Compressed
    • Discrete Discrete
    StringOPC, Query, Expression, Derived, Reference, Memory
    Deadband ModehistoricalDeadbandModeDefines how the deadband value is used. Possible values along with JSON names and descriptions are listed below:

    • Absolute Absolute : The deadband setting is considered to be an absolute value.
    • Percent Percent : The actual deadband is calculated as a percent of the Tag's engineering unit span.
    • Off Off :
      New in 8.1.2
      The deadband setting is the equivalent to a value of 0.0, so that all values pass through if their timestamp has changed.
    StringOPC, Query, Expression, Derived, Reference, Memory
    Historical DeadbandhistoricalDeadbandA deadband that applies only to historical evaluation.NumericOPC, Query, Expression, Derived, Reference, Memory
    Sample ModesampleModeDetermines how often a historical record should be collected. Possible values along with JSON names and descriptions can be found below.StringOPC, Query, Expression, Derived, Reference, Memory
    Sample RatehistorySampleRateWhen the Sample Mode property is set to "Periodic", this property (working in conjunction with the Sample Rate Units property) determines how often a record should be collected.NumericOPC, Query, Expression, Derived, Reference, Memory
    Sample Rate UnitshistorySampleRateUnitsWhen the Sample Mode property is set to "Periodic", this property (working in conjunction with the Sample Rate property) determines the unit of time that will be use in record collection. For a list of units, see the Units of Time section.StringOPC, Query, Expression, Derived, Reference, Memory
    Historical Tag GrouphistoryTagGroupWhen the Sample Mode property is set to "Tag Group", this property determines which Tag Group will be used to collect records.StringOPC, Query, Expression, Derived, Reference, Memory
    Min Time Between SampleshistoryTimeDeadbandMinimum time between records. Useful in restricting the number of records collected when the Sample Mode is set to "Tag Change". Prevents multiple consecutive Tag changes from triggering consecutive record collections. Works in conjunctions with the Min Time Units property. The Value is calculated off of the value timestamp.IntegerOPC, Query, Expression, Derived, Reference, Memory
    Min Time UnitshistoryTimeDeadbandUnitsUnits of time to use with the Min Time Between Samples property. For a list of units, see the Units of Time section.StringOPC, Query, Expression, Derived, Reference, Memory
    Max Time Between SampleshistoryMaxAgeMaximum time between samples. Works in conjunction with the Max Time Units property. If a sample has not been collected by the time range specified by these two properties, then a record will be collected on the next sample interval. Setting this value to 0 will disable automatic record collection. Default is 0.
    Note: This setting will be ignored if the Sample Mode is set to Tag Group, and the targeted Tag Group is using non-default values for its Max Time Between Samples setting. The implication being that non-default values on the Tag Group settings take precedence over this setting.
    IntegerOPC, Query, Expression, Derived, Reference, Memory
    Max Time UnitshistoryMaxAgeUnitsMaximum time in units. For a list of units, see the Units of Time section.StringOPC, Query, Expression, Derived, Reference, Memory

    Units of Time

    Unit of TimeJSON/Scripting Name
    MillisecondsMS
    SecondsSEC
    MinutesMIN
    HourHOUR
    DayDAY
    WeekWEEK
    MonthMONTH
    YearYEAR

    Runtime Properties

    In addition to properties listed in the Tag Editor, some properties are exposed as runtime properties in the Tag Browser. These properties are valid targets for component bindings and tag reads/writes.

    Most runtime properties are representations of properties that can be configured in the Tag Editor. However there are some properties only listed in the Tag Browser:

    PropertyDescription
    CanRead
    New in 8.1.8
    A read-only property that represents whether or not this tag can be read from the current security context. This is determined by looking at the read permission settings on the tag and the tag provider's permission settings.
    CanWrite
    New in 8.1.8
    A read-only property that represents whether or not this tag can be written to from the current security context. This is determined by looking at the write permission settings on the tag, the Read Only property, and the tag provider's permission settings.

    Custom Tag Properties

    Inductive University

    Custom Tag Properties

    Watch the video

    Custom Tag properties allow application designers to configure their own properties on Tags to store unique values on any Tag. Once added, a custom property can be referenced like any other Tag property via bindings, expressions, and scripts.

    Both the Perspective and Vision visualization systems can bind to custom properties. In the following example, we already have Array Tag. Now let's add a custom property.

    1. Open an existing Tag and select the Custom properties category.
    2. Click on the Add icon in the Tag Editor. This will open the Custom Property dialog box.
    3. Enter a Name for your property, select the Data Type, and click OK.


    4. When you open your Tag Browser and expand the My Array Tag, you'll see your Custom Property.

    Vision Client Tags

    Client Tags have the ability to be used as either Expression or SQL Query Tags. There is an Expression/SQL page in the Tag editor that allows you to select what type it is.

    PropertyBinding/Scripting NameDescriptionData TypeApplicable Tag Type
    OPC ServerOPCWriteBackServerThe server against which to subscribe the data point. Note: this property is only present on legacy tag imports, from 7.9 and earlierStringQuery, Expression
    OPC Item PathOPCWriteBackItemPathThe path to subscribe to on the server. Note: this property is only present on legacy tag imports, from 7.9 and earlierStringQuery, Expression
    QueryExpressionText area to build your query or expression.
    This is the code used by the Tag: either a SQL Query for Query Tags, or an Expression for Expression Tags.
    StringQuery, Expression
    Query TypeQueryTypeWhen the TagType property is set to 1, this property determines if the Tag should be a Memory, Expression, or Query Tag. A mapping of supported values is listed below:

    • Memory Tag : 0
    • Expression Tag : 1
    • Query Tag : 2
    .
    IntegerQuery, Expression, Memory
    DatasourceSQLBindingDatasourceThe default data source of the Tag provider.StringQuery