XML Files

The grammar given here is a simplified overview of the ECML language. ECML is a language based on XML. The ECML DTD is located in <bin_dir>/tools/ews/ChorusOS.dtd file.

Table 7-1 Semantics of Grammar in XML Files

[ a ]	means that the a element is optional and can be omitted
{ a | b }	means that either the a element or the b element can be used
a*	means that the a element can be repeated 0 or more times
a+	means that the a element can be repeated 1 or more times

The Attributes Tables in the sections below describe the XML attributes that can be used with the tags.

Configuration

This is the topmost scope level. A configuration must start with a <configuration> tag.

<configuration>
  [ <description> ] [ <typedef>* ] [{ <definition> | <feature> | <tunable> ]*
  [ <setting>* ] [ <action>* ] [ <constraint>* ]
  [{ <folder> | <folderRef> }]*

Table 7-2 Attributes for Configuration

Attribute	Description
name: string	Name of the configuration

Folder Declaration

A folder is used to scope variables, and to set up a hierarchy in the ChorusOS system configuration. A condition can be used on a folder to disable it (if the condition evaluates to false). Any element located in a disabled folder is also disabled.

<folder>
  [ <description> ] [ <typedef>* ] [ <definition> | <feature> | <tunable> ]*
  [ <setting>* ] [ <action>* ] [ <constraint>* ]
  [ <folder> | <folderRef> ]*

Table 7-3 Attributes for Folder

Attribute	Description
name: string	Name of the folder
visible: 'yes' or 'no'	Default: 'yes'. Specifies if a configuration tool should show this folder or not. If the folder is not visible, all of its content is hidden as well.

Folder Link

A folder link is used to include another file. This is used to split the configuration into several files.

<folderRef>  

Table 7-4 Attributes for Folder Link

Attribute	Description
href: URL	Path of the file to include
visible: 'yes' or 'no'	Default: 'yes'. Specifies if the content of the included file must be visible in a configuration tool.

Description

This is used to bind a description to an element. The description text can be displayed in a configuration tool.

<description> text

Definition

This is used to declare a variable. The declaration is fully typed, and can be conditioned by a <condition> boolean expression. If the condition evaluates to 'false', the variable is not declared.

<definition>
  [ <description> ] [ <condition> ] type_content [{ expression | <value>* }]

Table 7-5 Attributes of Definition

Attribute	Description
name: string	Name of the variable to declare
configurable: 'yes' or 'no'	Default: 'no'. Specifies if the value of this variable can be changed with a configuration tool.
visible: 'yes' or 'no'	Default: 'no'. Specifies if this variable declaration must be visible in a configuration tool.
global: 'yes' or 'no'	Default: 'yes'. Specifies if this variable is scoped into the folder where it is declared.

Feature

This is used to declare a ChorusOS system feature. A feature declaration has the same semantics as a variable declaration, but it is always visible, configurable, and global.

<feature>
  [ <description> ] [ <condition> ] type_content [ <const> | boolean_values ]

Table 7-6 Attributes for Feature

Attribute	Description
name: string	Name of variable to declare

Tunable

This is used to declare a ChorusOS system tunable. A tunable declaration has the same semantics as a variable declaration, but it is always visible, configurable, and global.

<tunable>
  [ <description> ] [ <condition> ] type_content [ <const> | boolean_const ]

Table 7-7 Attributes for Tunable

Attribute	Description
name: string	Name of the variable to declare

Boolean Constants

This defines the 'true' and 'false' boolean constants.

boolean_const
  { <true> | <false> }

Type Content

This is the set of types available for variable declarations.

type_content
  { <bool> | <int> | <string> | <enum> | <struct> | <list> | <type> }

Integers

This is used to declare a variable as an integer. An integer is assigned a value of 64 bits.

<int>

Table 7-8 Attribute for Integer

Attribute	Description
min: integer value	Minimum value authorized for this integer.
max: integer value	Maximum value authorized for this integer.

String

This is used to declare a variable as a string.

<string>

Enumerations

This is used to declare an enumerated value. The <const> sub-elements define all the possible values of the enumeration.

<enum>
  <const>+

Structures

This is used to declare a structured variable.

<struct>
  <field>+

Structure Fields

This is used to describe the characteristics of a structure field.

<field>
  [ <description> ] type_content expression

Table 7-9 Attributes of Field

Attribute	Description
name: string	Name of the field
optional: 'yes' or 'no'	Default 'no'. Specifies if this field can be omitted when setting the initial value of a variable in its declaration.
ref-only: 'yes' or 'no'	Default 'no'. Specifies if this field contains only a references to another variable.

Lists

Used to declare a list variable. The type_content sub-element is used to type the element of the list.

Table 7-10 Attributes of List

Attribute	Description
ref-only: 'yes' or 'no'	Specifies if this list only contains references to other variables.

Boolean Expressions

Boolean expressions are written in a post-fixed notation. They are used wherever a boolean result is expected.

boolean_expression
  { boolean_const | <and> | <or> | <not> | <equal> | <notequal> |
    <ifdef> | <imply> }

Expressions

Generic expressions are an extension of boolean expressions which can produce variable reference, string, or enumeration constants.

expression
  { boolean_expression | <ref> | <vstring> | <const> }

Variable Reference

This is used to reference another variable by its name. The variable must be declared and accessible in the scope of this reference.

<ref>

Table 7-11 Attributes of Variable Reference

Attribute	Description
name:string	Name of the referenced variable.

Test of Variable Existence

This test returns true if the specified variable exists or has been declared.

<ifdef>

Table 7-12 Attribute of Variable Existence

Attribute	Description
name: string	Name of the referenced variable.

Variable value

This allows you to get the current value of a variable. The specified variable must have been declared previously.

<var>

Table 7-13 Attributes of Variable Value

Attribute	Description
name: string	Name of the variable.

Conditions

A condition is used to validate or invalidate an element.

<condition>
  boolean_expression

Typedef

This declares a new type. A type definition is global in the configuration, and can be used in a 'type' reference.

<typedef>
  [ <description> ] type_content

Type

This is used to reference a type definition.

<type>

Table 7-14 Attributes of Type

Attribute	Description
name: string	Name of the referenced type. This type must have been declared in a typeDef.
ref-only: 'yes' or 'no'	Specifies if this type denotes a reference.

Settings

This is the assignment of a variable . The named variable is assigned with the given value. The variable must already have been declared before, and the value must have a correct type.

<setting>
  [ <description> ] [ <condition> ] type_content { expression | <value>* }

Table 7-15 Attribute of Setting

Attribute	Description
name: string	Name of variable

Constraints

A constraint is a boolean expression used to ensure the integrity of the configuration. If a constraint has a false value, the configuration tool considers the configuration to be invalid, and not to be used to generate a ChorusOS system image.

<constraint>
  [ <description> ] boolean_expression

Table 7-16 Attribute of Constraint

Attribute	Description
name: string	Name of the constraint.

Actions

An action takes a parameter which specifies the precise effect that will be performed by a configuration tool.

<action>
  [ <description> ] [ <condition> ] <application> {<definition>|expression}

Table 7-17 Attribute of Action

Attribute	Description
name: string	Name of the action

Action Application

This determines which action of the configuration tool will be applied. Currently, only the configure application exists and uses a variable typed as Configure structure as a parameter.

<application>
   text