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.

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

On this page ...

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 Object	Type
Property	A single value underneath an node.
Node	An 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.
Folder	Represented 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.
AtomicTag	A "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
UdtInstance	An 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.
UdtType	Represents 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.
Provider	Represents 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.

Property

JSON/Scripting Name

Description

Data Type

Applicable Tag Type

Basic Properties

Name name How the Tag will be presented and referenced in the system. The Tag path will be the provider, the folder structure, and this name. String OPC, Query, Expression, Derived, Client, Reference, Memory

Tag Group tagGroup The 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. String OPC, Query, Expression, Derived, Reference, Memory

Enabled enabled Whether the Tag will be evaluated by the Tag Group. If false, the Tag will still be present, but will have a bad quality. Boolean OPC, Query, Expression, Derived, Reference, Memory

Value

Value Source

valueSource

Specifies how the Tag determines its value. In other words, sets the type of the Tag (Memory, OPC, Expression, etc).

Click here to see valid values

Value Source	JSON Name
Derived	derived
Expression	expr
Memory	memory
OPC	opc
Query	db
Reference	reference

String

OPC, Query, Expression, Derived, Reference, Memory

Data Type

dataType

The 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, see Tag Data Types.

Click here to see valid values

Data Type	String Value	Integer Value
Byte	Int1	0
Short	Int2	1
Integer	Int4	2
Long	Int8	3
Float	Float4	4
Double	Float8	5
Boolean	Boolean	6
String	String	7
DateTime	DateTime	8
Text	Text	10
Byte Array	Int1Array	17
Short Array	Int2Array	18
Integer Array	Int4Array	11
Long Array	Int8Array	12
Float Array	Float4Array	19
Double Array	Float8Array	13
Boolean Array	BooleanArray	14
String Array	StringArray	15
DateTime Array	DateTimeArray	16
Binary Data	ByteArray	20
Dataset	DataSet	9
Document	Document	29

Note: Regarding Array data types, Alarming, Scaling, and Historical settings applied to an array Tag are propagated down to elements in the array.

String

OPC, Query, Expression, Derived, Reference, Memory

Value

value

The 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 Server opcServer Only p resent for OPC Tags. The server against which to subscribe the data point. Only present for OPC Tags. String OPC

OPC Item Path

opcItemPath

Only 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.

The following feature is new in Ignition version 8.1.5
Click here to check out the other new features

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.

String

OPC

Source Tag Path sourceTagPath The path to the Tag that this Tag is referencing. Only present for Reference and Derived Tags. String Derived, Reference

Execution Mode

executionMode

Only present for Query and Expression Tags . Determines how when the Tag executes.

Event Driven - Updates when something happens (i.e., value event or alarm event) within the expression.
Fixed Rate - 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 - Tags are executed by Tag Groups, which dictate the rate of execution.

Execution Mode	JSON Name
Event Driven	EventDriven
Fixed Rate	FixedRate
Tag Group	TagGroupRate

String

Expression, Query

Expression

expression

The expression the Tag will use to determine its value.

String

Expression

Read Expression

deriveExpressionGetter

The expression that determines how the value on the Derived Tag is displayed.

String

Derived

Query query The 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.

Write Expression

deriveExpressionSetter

The expression that determines how the value on the Derived Tag is displayed.

String

Derived

Datasource

datasource

The database connection that the query Tag will execute against.

String

Query

Query Type

queryType

The following feature is new in Ignition version 8.1.3
Click here to check out the other new features

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.

String

Query

Numeric Properties

Deadband deadband A numerical value used to prevent unnecessary updates for Tags whose values change by small amounts. Numeric OPC, Query, Expression, Derived, Reference, Memory

Deadband Mode

deadbandMode

Defines how the deadband value is used.

Absolute - The deadband setting is considered to be an absolute value.
Percent - The actual deadband is calculated as a percent of the Tag's engineering unit span.

Valid values are as follows:

Deadband Mode	JSON Name
Absolute	Absolute
Percent	Percent

String

OPC, Query, Expression, Derived, Reference, Memory

Scale Mode

scaleMode

If and how the Tag value will be scaled between the source, and what is reported for the Tag.

Valid values are as follows:

Mode	JSON Name	Int Value
Off	Off	0
Linear	Linear	1
Square Root	SquareRoot	2
Exponential Filter	ExponentialFilter	3
Bit Inversion	BitInversion	4

String

OPC, Query, Expression, Derived, Reference, Memory

Raw Low rawLow Start of the "raw" value range. Only present if Scale Mode is set to Linear or Square Root. Numeric OPC, Query, Expression, Derived, Reference, Memory

Raw High

rawHigh

End of the "raw" value range. Only present if Scale Mode is set to Linear or Square Root.

Numeric

OPC, Query, Expression, Derived, Reference, Memory

Scaled Low scaledLow Start 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. Numeric OPC, Query, Expression, Derived, Reference, Memory

Scaled High scaledHigh End 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. Numeric OPC, Query, Expression, Derived, Reference, Memory

Clamp Mode

clampMode

How 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.

Valid values are as follows:

Clamp Mode	JSON Name	Int Value
No_Clamp	No_Clamp	0
Clamp_Low	Clamp_Low	1
Clamp_High	Clamp_High	2
Clamp_Both	Clamp_Both	3

String

OPC, Query, Expression, Derived, Reference, Memory

Scale Factor scaleFactor For single parameter modes (currently only Exponential Filter), the factor parameter for the equation. Used when the Scale Mode property is set to Exponential Filter Numeric OPC, Query, Expression, Derived, Reference, Memory

Engineering Units engUnit The engineering units of the value. String OPC, Query, Expression, Derived, Reference, Memory

Engineering Low Limit engLow The lowest expected value of the Tag. Numeric OPC, Query, Expression, Derived, Reference, Memory

Engineering High Limit engHigh The highest expected value of the Tag. Numeric OPC, Query, Expression, Derived, Reference, Memory

Engineering Limit Mode

engLimitMode

Dictates 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.

Valid values are as follows:

Limit Enforcement	JSON Name	Int Value
No_Clamp	No_Clamp	0
Clamp_Low	Clamp_Low	1
Clamp_High	Clamp_High	2
Clamp_Both	Clamp_Both	3

Numeric

OPC, Query, Expression, Derived, Reference, Memory

Format String

formatString

How 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.

String

OPC, Query, Expression, Derived, Reference, Memory

Meta Data Properties

Tooltip tooltip The 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. String OPC, Query, Expression, Derived, Reference, Memory

Documentation

documentation

A freeform text property for information about the Tag.

String

OPC, Query, Expression, Derived, Reference, Memory

Security

Read Permissions

readPermissions

Defines the security levels required in order to read values from a Tag. For more information, see Tag Security Properties. Contains the following elements:

Name

JSON Name

Description

Type

type

Represents 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 Levels

securityLevels

Represents 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.

Click here to see an example in JSON...

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": []
          }
        ]
      }
    ]
  }

JSON Object

OPC, Query, Expression, Derived, Reference, Memory

Read Only

readOnly

Defines whether a Tag is read-only or writeable. For more information, see Tag Security Properties.

value: boolean

OPC, Query, Expression, Derived, Reference, Memory

Write Permissions

writePermissions

Defines the security levels required in order to read values from a Tag. For more information, see Tag Security Properties. Contains the following elements:

Name JSON Name Description

Type

type

Represents 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 Levels

securityLevels

Represents 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.

Click here to see an example in JSON...

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.

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

JSON Object

OPC, Query, Expression, Derived, Reference, Memory

Scripting

Tag Event Scripts

eventScripts

Each 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 in the expandable area below:

Click here to expand...

Key Description

Key	Description
eventid	A value representing the type of event script
script	A value representing the content of the script

Possible eventid values

Event Script	eventid value
Quality Changed	qualityChanged
Value Changed	valueChanged
Alarm Active	alarmActive
Alarm Cleared	alarmCleared
Alarm Acknowledged	alarmAcked

JSON Array

OPC, Query, Expression, Derived, Reference, Memory

Alarms

Alarms

alarms

Tags 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 Enabled

alarmEvalEnabled

Determines if alarms will be evaluated on this tag.

Boolean

OPC, Query, Expression, Derived, Reference, Memory

History

History Enabled historyEnabled Whether the Tag will report its history to the Tags Historian system. Boolean OPC, Query, Expression, Derived, Reference, Memory

Storage Provider historyProvider Which 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. String OPC, Query, Expression, Derived, Reference, Memory

Deadband Style

historicalDeadbandStyle

There 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.

Valid values are as follows:

Deadband Style	JSON Name
Auto	Auto
Analog	Analog
Discrete	Discrete

String

OPC, Query, Expression, Derived, Reference, Memory

Deadband Mode

historicalDeadbandMode

Defines how the deadband value is used.

Absolute - The deadband setting is considered to be an absolute value.
Percent - The actual deadband is calculated as a percent of the Tag's engineering unit span.

Deadband Mode	JSON Name
Absolute	Absolute
Percent	Percent

String

OPC, Query, Expression, Derived, Reference, Memory

Historical Deadband

historicalDeadband

A deadband that applies only to historical evaluation.

Numeric

OPC, Query, Expression, Derived, Reference, Memory

Sample Mode

sampleMode

Determines how often a historical record should be collected.

On Change - Collects a record whenever the value on the Tag changes.
Periodic - Collects a record based on the Sample Rate and Sample Rate Units properties.
Tag Group - Collects a record based on the Tag Group specified under the Historical Tag Group property.

Valid values are as follows:

Max Time Between Records Mode	JSON Name
On Change	OnChange
Periodic	Periodic
Tag Group	TagGroup

String

OPC, Query, Expression, Derived, Reference, Memory

Sample Rate

historySampleRate

When 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.

Numeric

OPC, Query, Expression, Derived, Reference, Memory

Sample Rate Units

historySampleRateUnits

When 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.

Click here to see valid values

Unit of Time	JSON Name
Milliseconds	MS
Seconds	SEC
Minutes	MIN
Hour	HOUR
Day	DAY
Week	WEEK
Month	MONTH
Year	YEAR

String

OPC, Query, Expression, Derived, Reference, Memory

Historical Tag Group

historyTagGroup

When the Sample Mode property is set to "Tag Group", this property determines which Tag Group will be used to collect records.

String

OPC, Query, Expression, Derived, Reference, Memory

Min Time Between Samples

historyTimeDeadband

Minimum 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.

Integer

OPC, Query, Expression, Derived, Reference, Memory

Min Time Units

historyTimeDeadbandUnits

Units of time to use with the Min Time Between Samples property.

Click here to see valid values

Unit of Time	JSON Name
Milliseconds	MS
Seconds	SEC
Minutes	MIN
Hour	HOUR
Day	DAY
Week	WEEK
Month	MONTH
Year	YEAR

String

OPC, Query, Expression, Derived, Reference, Memory

Max Time Between Samples


                historyMaxAge

Maximum 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.

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.

Integer

OPC, Query, Expression, Derived, Reference, Memory

Max Time Units

historyMaxAgeUnits

Maximum time in units is defined as: Milliseconds, Seconds, Minutes, Hours, Days, Weeks, Months, and Years.

Click here to see valid values

Unit of Time	JSON Name
Milliseconds	MS
Seconds	SEC
Minutes	MIN
Hour	HOUR
Day	DAY
Week	WEEK
Month	MONTH
Year	YEAR

String

OPC, Query, Expression, Derived, Reference, Memory

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:

Property	Description
CanRead	The following feature is new in Ignition version 8.1.8 Click here to check out the other new features 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	The following feature is new in Ignition version 8.1.8 Click here to check out the other new features 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

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.

Open an existing Tag and click on the Add icon in the Tag Editor.
This opens the Custom Property dialog box. Enter a Name for your Tag, select the Data Type, and click OK.
Scroll down to the bottom of your Tag properies and you'll see your Custom Property. We added the value "Hello Ignition".
When you open your Tag Browser and expand the My Array Tag, you'll see your Custom Property.

Custom Tag Properties

Watch the Video

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.

Query/Expression Attributes

Property

Binding/Scripting Name

Description

Data Type

Applicable Tag Type

OPC Server

OPCWriteBackServer

The server against which to subscribe the data point.

String

Query, Expression

OPC Item Path

OPCWriteBackItemPath

The path to subscribe to on the server.

String

Query, Expression

Query

Expression

Text area to build your query or expression.

String

This is the code used by the Tag: either a SQL Query for Query Tags, or an Expression for Expression Tags.

Query, Expression

Query Type

QueryType

When the TagType property is set to 1, this property determines if the Tag should be a Memory, Expression, or Query Tag.

Integer

Click here to see supported values

Tag Type	Integer Value
Memory Tag	0
Expression Tag	1
Query Tag	2

Query, Expression, Memory

Datasource

SQLBindingDatasource

The default data source of the Tag provider.

String

Query

Contents

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Employees

Tag Configuration in the Designer

Tag Object Types

Standard Tag Properties Table

Property

JSON/Scripting Name

Description

Data Type

Applicable Tag Type

Runtime Properties

Custom Tag Properties

Vision Client Tags

Query/Expression Attributes

Property

Binding/Scripting Name

Description

Data Type

Applicable Tag Type