This topic describes the syntax rules for referring to properties and for creating expressions within various DTL actions.
When you assign a value to a target property, you often specify a literal value. Literal values are also sometimes suitable in other places, such as the value in a trace action.
A literal value is either of the following:
XML Reserved Characters
Because DTL transformations are saved as XML documents, you must use XML entities in the place of XML reserved characters:
|To include this character...
|Use this XML entity...
For example, to assign the value Joe’s "Good Time" Bar & Grill to a target property, set Value equal to the following:
"Joe's "Good Time" Bar & Grill"
This restriction does not apply inside code and sql actions, because InterSystems IRIS® automatically wraps a CData block around the text that you enter into the editor. (In the XML standard, a CData block encloses text that should not be parsed as XML. Thus you can include reserved characters in that block.)
Separator Characters in Virtual Documents
In most of the virtual document formats, specific characters are used as separators between segments, between fields, between subfields, and so on. If you need to include any of these characters as literal text when you are setting a value in the message, you must instead use the applicable escape sequence, if any, for that document format.
See the following topics:
In a data transformation, the separator characters and escape sequences can be different for the source and target messages. InterSystems IRIS automatically adjusts values as needed, after performing the transformation. This means that you should consider only the separator characters and escape sequences that apply to the source message.
When XML Reserved Characters Are Also Separators
If the character (for example, &) is a separator and you want to include it as a literal character, use the escape sequence that applies to the virtual document format.
In all other cases, use the XML entity as shown previously in XML Reserved Characters.
Numeric Character Codes
You can include decimal or hexadecimal representations of characters within literal strings.
The string &#n; represents a Unicode character when n is a decimal Unicode character number. One example is é for the Latin e character with acute accent mark (é).
Alternatively, the string &#xh; represents a Unicode character when h is a hexadecimal Unicode character number. One example is ¿ for the inverted question mark (¿).
When you assign a value to a target property, you can specify an expression, in the language that you selected for the data transformation. You also use expressions in other places, such as the condition for an if action, the value in a trace action, statements in a code action, and so on.
The following are all valid expressions:
Literal values, as described in the previous section.
Function calls (InterSystems IRIS provides a set of utility functions for use in business rules and data transformations. For details, see Utility Functions for Use in Productions.) InterSystems IRIS provides a wizard for these.
References to properties, as described in References to Properties.
References to the aux variable passed by the rule. If the data transformation is called from a rule, it supplies the following information in the aux variable:
aux.BusinessRuleName—Name of the rule.
aux.RuleReason—Reason that the rule was fired. It is the same name as used in the logging. An example value is 'rule#1:when#1'. If the RuleReason is longer than 2000 characters, it is truncated to 2000 characters.
aux.RuleUserData—Value that was assigned in the rule to the property 'RuleUserData'. The value of 'RuleUserData' is always the last value that it was set to.
aux.RuleActionUserData—Value that was assigned in the rule when or otherwise clause to the property 'RuleActionUserData’.
If the data transformation is called directly from code and not from a rule, the code can pass the auxiliary data in the third parameter. If your data transformation may be called from code that does not set the third parameter, your DTL code should check that the aux variable is an object in an if action using the $ISOBJECT function.
Any expression that combines these, using the syntax of the scripting language you chose for data transformation. See Specifying Transformation Details. Note the following:
In ObjectScript, the concatenation operator is the _ (underscore) character, as in:
To learn about useful ObjectScript string functions, such as $CHAR and $PIECE, see the ObjectScript Reference.
For a general introduction, see Using ObjectScript.