User Guide

How MXML relates to standards 41
MXML tag syntax
MXML has the following syntax requirements:
• The id property is not required on any tag.
• The id property is not allowed on the root tag.
• Boolean properties only take true and false values.
• The <mx:Binding> tag requires both source and destination properties.
• The <mx:Binding> tag cannot contain an id property.
• The <mx:Validator> tag and its subclasses require a field property.
• The <mx:Validator> tag cannot contain an id property.
• The <mx:WebService> tag requires either a wsdl value or serviceName value, and does not
allow both.
• The <mx:RemoteObject> tag requires either a source value or a named value, and does not
allow both.
• The <mx:HTTPService> tag requires either a url value or a serviceName value, and does not
allow both.
• The <mx:operation> tag requires a name value, and does not allow duplicate name entries.
• The <mx:operation> tag cannot contain an id property.
• The <mx:method> tag requires a name value and does not allow duplicate name entries.
• The <mx:method> tag cannot contain an id property.
How MXML relates to standards
MXML uses standards extensively. This section describes how MXML relates to standards for
the following:
• XML
• Event models
• Web services
• Java
• HTTP
• Graphics
• Cascading Style Sheets
XML standards
You write Flex applications in XML documents. XML documents use tags to define pieces of
structured information and the relationships between them. In MXML, the
<mx:Application>
tag defines the root of an application. You define the parts of the application in child tags of the
<mx:Application> tag. Examples of MXML tags include container tags, such as <mx:VBox>,
which define rectangular regions of the user interface, and control tags, such as
<mx:TextInput>,
which define typical user interface controls.