ION Syntax Conventions

Tag Pair: <TAG> content </TAG>

Single Tag: <TAG/>

Note
It is important to note that single tags are closed with />. Don't forget the /, or you will get a syntax error.

The following table lists which ION Script tags are tag pairs, and which are single tags:

Table 5-1: ION Script Tag Pairs

Table 5-1: ION Script Tag Pairs
Tag Pairs	Single Tags
<EVENTS> ... </EVENTS>	<EVENT_DECL />
<IDL> ... </IDL>	<ION_BUTTON />
<ION_BODY> ... </ION_BODY>	<ION_CHECKBOX />
<ION_DATA_OUT> ... </ION_DATA_OUT>	<ION_EVALUATE />
<ION_FORM> ... </ION_FORM>	<ION_ELSE />
<ION_HEADER> ... </ION_HEADER>	<ION_ELSEIF />
<ION_IF> ... </ION_IF>	<ION_INCLUDE />
<ION_IMAGE> ... </ION_IMAGE>	<ION_PARAM />
<ION_LINK> ... </ION_LINK>	<ION_RADIO />
<ION_OBJECT> ... </ION_OBJECT>	<ION_VARIABLE />
<ION_SCRIPT> ... </ION_SCRIPT>	<VARIABLE_DECL />
<VARIABLES> ... </VARIABLES>

Elements of Syntax

Each tag listed in this reference includes a "Syntax" section that defines how the tag is used. The following elements are used in syntax listings:

Table 5-2: ION Script Syntax Elements

Table 5-2: ION Script Syntax Elements
Element	Description
[ ] (Square brackets)	Indicates that the contents are optional.
Italics	Indicates arguments, expressions, or statements for which you must provide values.
{ } (Braces)	Indicates that you must choose one of the values they contain.
\| (Vertical lines)	Separates values from which you must choose.

In this example, ATTRIBUTE1 is required, while all other attributes are optional. ATTRIBUTE3 can be set to either value1 or value2.

Square Brackets ( [ ] )

Content between square brackets is optional.

Do not include square brackets in your statement.

Note
Square Brackets are used in IDL to define an array. When including IDL code as the value of an ION Script tag attribute or the content of an ION Script tag, square brackets that are part of the IDL code must be included. For example, the <IDL> tag might be used as follows:

<IDL> MyArray = [1,2,3,4,5] </IDL>

In this case, the square brackets are included in the statement because they are part of the IDL syntax.

Braces ( { } )

Braces are used to enclose a list of the possible values for an attribute. You must choose one of the listed values, which are separated by a vertical line ( | ). Do not include the braces in your statement. For example, the following syntax indicates that you must choose either TRUE or FALSE for the DISPLAY attribute (if you choose to use DISPLAY):

<ION_EVALUATE EXPR="$X * 5" DISPLAY="TRUE" />

Italics

Italicized words are place-holders for values that you must provide for attributes, as well as for HTML or IDL content.

Case Sensitivity

ION Script is case-sensitive. All ION Script tags and attributes must be entered exactly as shown in this reference. User-defined variables must use consistent case as well. If you declare a variable as $A, you cannot refer to that variable using $a. System variables are not case-sensitive, except for $Browser system variables.

Using Quotation Marks

ION Script requires that values assigned to tag attributes be enclosed in double quotation marks, using the general form ATTRIBUTE="value".

When the attribute is an expression (the EXPR attribute of ION_DATA_OUT or ION_IF), you will often need to mix numeric and string values. Strings can be enclosed in single quotation marks, which can be nested inside double quotation marks, as in the following example:

Single quotation marks must also be nested inside double quotation marks whenever you assign a string literal as the value of an ION Script variable. For example, the following code shows the correct way to assign a string literal to the VALUE attribute of the VARIABLE_DECL tag:

<VARIABLE_DECL NAME="animal" TYPE="STR" VALUE="'dog'"/>

Variable Substitution in Attribute Values

Many ION Script tag attributes can be set to values that contain explicit values and/or variables. For example, the EVENT attribute could be set in the following ways:

To an explicit value:

	EVENT="http://myserver/page1.html"

To a variable:

	EVENT="$MyURL"

To a combination of explicit values and variables:

	EVENT="http://myserver/$mypage"

If an attribute can contain a variable, this fact is indicated in the attribute description.

HTML tag attributes can also contain variables, but you must insert the variable into the HTML attribute by using the ION_VARIABLE tag. For example, the HTML <FONT> tag could be specified as follows:

<ION_HEADER>  
<VARIABLES>  
   <VARIABLE_DECL NAME="FontColor" TYPE="STR" VALUE="'Red'"/>  
</VARIABLES>  
</ION_HEADER>  
<ION_BODY>  
   <FONT COLOR="<ION_VARIABLE NAME="$FontColor"/>">  
   This should be Red  
   </FONT>  
</ION_BODY>

IDL Online Help (March 06, 2007)