data_dictionary.html

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">

<!--
 Documentation of Defining a Data Dictionary.
 
 @author becker
 @ConQAT.Rating GREEN Hash: C359C5FBF27AA4D36ECA49D9504DA64A
-->
 
<html>
<head>
	<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
	<title>Defining a Data Dictionary using AutoFOCUS3 (AF3)</title>
</head>
<body>

<h2><u><font color="#336699">Data Dictionary: Types and functions</font></u></h2>

AF3 allows you to define your own datatypes and functions by using a socalled "Data Dictionary".
<br>
To create such a Data Dictionary, right-click at the root of your project and select "Data Dictionary", as shown below:

<br><br>
<img src="./pictures/DataDictionary.Add.png">
<br><br>

You can then add the following elements to your Data Dictionary:
<ul>
<li>Enumeration</li>
<li>Structure</li>
<li>Array</li>
<li>Function</li>
</ul>
These can be added by drag-and-drop from the model elements palette or by the context menu (right-click)
<br>of the data dictionary itself in the model navigator. 

We describe below every of these elements in more details: what they consist of, how to define them,
<br>as well as the <i>syntax</i> to use to refer to the data items they define. The latter is particularly
<br>useful, e.g., in Guards and Actions of <a href="state_automaton.html"><i>State Automata</i></a>, in <a href="code_specification.html"><i>Code Specifications</i></a>,
or in <a href="tl_specification.html"><i>Temporal Logic Specifications</i></a>.

 <h3>Enumeration</h3>

An enumeration is a data type defined as a finite list of values. Variables of this type can only contain a value which belong to this list.
<br>This is similar to "unions" in C, or to "sum types" in functional languages.
<br>After having created an enumeration, you can add elements to it by drag and dropping "enumeration members" from the
<br>palette or by right-clicking the enumeration in the data dictionary editor.

<p><i>Syntax</i>: an enumeration member can be accessed by writing its name followed by "()" (this allows to distinguish enumeration members from ports).
<br>For instance, referring to the elements of the enumeration defined below is done by writing "Green()", "Red()", "RedYellow()", "Yellow()".

<br>
<img src="./pictures/DataDictionary.Enumeration.png">
<br><br>

<h3>Structure</h3>

A structure is a data type which allows to gather various values in one variable, each value being uniquely identified by a structure member <i>name</i>.
<br>One can for instance state a value shall always have a member called "x" of type integer and a member called "y" of type boolean.
<br>This is similar to "records" in C, or to "product types" in functional languages.
<br>After having created a structure, you can add elements to it by drag and dropping "structure members" from the
<br>palette or by right-clicking the structure in the data dictionary editor.

<p><i>Syntax</i>: a structure member of a variable "v" can be accessed by writing "v.MEMBER_NAME".
<br>For instance, for the example structure mentioned in the previous paragraph, one would access the integer by "v.x" and the boolean by "v.y".
<br>Creating a structure is done with the syntax "{member_name_1: value_1, member_name_2: value_2, ...}". With the same example above: "{ x: 1, y: true }".
</p>


<h3>Array</h3>

Arrays are like usual C arrays, but <i>their size is defined in the datatype itself</i>.

<p><i>Syntax</i>: Given a variable "v" whose type is an array, the i-th element can be accessed by the expression
<br>"v[i]". The index starts from 0. Assigning a value x to the i-th element is done with the syntax "v[i] = x".</p>

<h3>Function</h3>

Functions denote small functions which can be used in various places in an AF3 project.
<br><i>Note:</i>Functions are not a type but are still defined in the data dictionary.

<p>Functions have:
<ul>
<li>parameters
<li>a return type
<li>a definition

<i>Note:</i> the definition cannot contain local variables!
<br>(this means that practically, most function definitions contain only "if" and "return" statements.)
</ul>
(see next figure for an example). 
</p>

<img src="./pictures/DataDictionary.Definitions.png">
<br><br>

<h3>Evaluator</h3>
If you want to check your defined functions, AutoFOCUS provides an Evaluator for the Data Dictionary.
<br>Simply click onto the Evaluator-Tab and insert commands into the lower field. The upper field shows the results of your inputs. 
<br>As you can see in the following Example, the Function "tRed()" returns 5 as defined. 

<br><br>
<img src="./pictures/DataDictionary.Evaluator.png">
<br><br>

</font>
</body>
</html>