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

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.

Basic Properties

Property	JSON/Scripting Name	Description	Data Type	Applicable Tag Type
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

Property	JSON/Scripting Name	Description	Data Type	Applicable Tag Type
Value Source	valueSource	Specifies how the Tag determines its value. In other words, sets the type of the Tag (Memory, OPC, Expression, etc). The following lists valid value sources and their JSON Name: Reference: reference Query: db OPC: opc Memory: memory Expression: expr Derived: derived	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. 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. ​ 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.	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. 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	​ 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.	String	Query

Valid Data Type 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

Numeric Properties

Property	JSON/Scripting Name	Description	Data Type	Applicable Tag Type
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: 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: 0- Off: Off 1- Linear: Linear 2- Square Root: SquareRoot 3- Exponential Filter: ExponentialFilter 4- Bit Inversion: BitInversion	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: 0 - No_Clamp: No_Clamp 1 - Clamp_Low: Clamp_Low 2 - Clamp_High: Clamp_High 3 - Clamp_Both: Clamp_Both	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: 0 - No_Clamp: No_Clamp 1 - Clamp_Low: Clamp_Low 2 - Clamp_High: Clamp_High 3 - Clamp_Both: Clamp_Both	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

Property	JSON/Scripting Name	Description	Data Type	Applicable Tag Type
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

Property	JSON/Scripting Name	Description	Data Type	Applicable Tag Type
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: 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.  Click here to see an example in JSON...	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: 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.  Click here to see an example in JSON...	JSON Object	OPC, Query, Expression, Derived, Reference, Memory

Read Permissions 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": []
          }
        ]
      }
    ]
  }                                                                                                                                                    

Write Permissions 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.

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

Scripting

Property	JSON/Scripting Name	Description	Data Type	Applicable Tag Type
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. Key Description: eventid: A value representing the type of event script script: A value representing the content of the script Possible eventid values: Quality Changed: qualityChanged Value Changed: valueChanged Alarm Active: alarmActive Alarm Cleared: alarmCleared Alarm Acknowledged: alarmAcked	JSON Array	OPC, Query, Expression, Derived, Reference, Memory

Alarms

Property	JSON/Scripting Name	Description	Data Type	Applicable Tag Type
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

Property	JSON/Scripting Name	Description	Data Type	Applicable Tag Type
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: Auto: Auto Analog: Analog Discrete: Discrete	String	OPC, Query, Expression, Derived, Reference, Memory
Deadband Mode	historicalDeadbandMode	Defines how the deadband value is used. 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.	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 (OnChange) - Collects a record whenever the value on the Tag changes. Periodic (Periodic) - Collects a record based on the Sample Rate and Sample Rate Units properties. Tag Group (TagGroup) - Collects a record based on the Tag Group specified under the Historical Tag Group property.	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. 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. 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. 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	​ 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

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 click on the Add icon in the Tag Editor.

2. This opens the Custom Property dialog box. Enter a Name for your Tag, select the Data Type, and click OK.

   

3. Scroll down to the bottom of your Tag properies and you'll see your Custom Property. We added the value "Hello Ignition".

   

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.

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 Supported tag types and their integer values include: Memory Tag: 0 Expression Tag: 1 Query Tag: 2	Query, Expression, Memory
Datasource	SQLBindingDatasource	The default data source of the Tag provider.	String	Query