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[[Category: Analytica Scripting Guide]]
[[Category: Objects]]
[[Category: Attributes]]

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===Creating New Objects===
An Analytica model consists of a set of '''''Objects''''', such as variables, modules, and functions. The Analytica language also contains Objects, including attributes, system functions, and commands.  Each object has a unique Identifier, and a set of properties known as Attributes.  For example, a Variable has a Title, Units, Description, and Definition attribute.   Each object belongs to a general category, called a Class.  Object classes include variables, functions, modules, and attributes.

You can create new objects of the following base classes: variable, Function, attribute, and model.  Some classes form a hierarchy.  There are additional variable and model classes.  The usual way to create a new object is to specify the Object class, followed by a unique identifier.  For example, in the Typescript window:

:<code>Example>variable life</code>  

<tip title="Note">Analytica will not be able to evaluate variables in the :model until it understands the definitions of all of the objects it contains.</tip>

When creating a new object, you should also specify the following '''user-specified attributes''' by default:

'''Variable'''  Title, Units, Description, Definition.<br>
'''Module'''    Title, Description, Author.<br>
'''Attribute''' Title, Description.<br>
'''Function'''  Title, Description, Definition, Parameters.<br>
'''Button'''    Title, Description, Script.<br>
 
==Attribute values That are Longer Than One Line==

User-specified attributes may be longer than one line.  To continue a Definition, Description, or other attribute over several lines, you place a tilde (“~”) or continuation character (option-L, “¬”) at the end of each line to be continued (Analytica will finish the Description or Definition when it receives a line that does not end with a tilde).

Analytica will also allow you to continue an attribute over several lines if you leave an open parenthesis on the first line of the attribute.  When you close the parentheses, Analytica will assume that you have finished typing in the attribute.

*Note	When entering attributes using the Analytica user interface (the Object window, Diagram window etc.), you do not need to specify a continuation character.
	
In ADE, it is best to build a large string, and then pass that string directly to the Command property, without using the continuation characters.  For example,

:<code>s = “very long string…..”</code> 
:<code>Ana.Command = “title: “ & s</code>
:<code>Ana.Send</code>
 
==Object classes==
As an Analytica user, you can create objects of these classes as part of a model:

* '''Variable''': An element of a model that can have a value. Variable has subclasses Chance, Decision, Objective, Index, and Determ.

* '''Module''': An object that contains a set of variables and other user-defined objects. A Model, Library, LinkModule, and LinkLibrary are subclasses of Module.

* '''Function''': A user-defined mathematical function that may have one or more parameters and returns a value.

* '''Alias''': A node in a diagram that depicts an object in a different module -- and so whose original node is in a different diagram. The text in an Alias node is italic.

* '''Attribute''': A property of an object, such as Class, Title, Identifier, or Description.

The Analytica language includes objects of these classes, which you cannot create: 

* '''Command''': An instruction to Analytica. You may use commands used only in [[Typescript]], not in normal Analytica expression.

* '''Keyword''': A textual word used in some language constructs -- such as,  IF THEN ELSE, FOR DO, or BEGIN END. 

* '''Sysfunction''': A standard built-in function, such as Sine (Sin), Standard Deviation (SDeviation), etc.

* '''Sysvar''': A pre-defined variable that controls formats or options, or designates version. Examples include: AnalyticaEdition, Run, SampleSize, and Time.

Classes are organized into a hierarchy, where subclasses inherit properties of their parent classes:

[[Image:Class Hierarchy.PNG]]

==Identifiers==

Each object has a unique identifier {{Release|6.5||within its namespace. Identifiers can start with letters (Unicode categories Ll, Lm, Lo, Lt, Lu) and "letter numbers" (Unicode category Nl). Some built-in or internal identifiers start with an underscore '_', but user identifiers cannot. After the first character, subsequent characters include all the starting categories as well digits, underscores and Unicode categories Mc, Mn, Nd and Pc (spacing marks, non-spacing marks, decimal numbers and connector punctuation). These categories capture a natural sense of words in pretty much any language. In general, you can't use spaces or punctuation characters in identifiers (but you can in titles). You can also use [[Identifier#Backquotes_for_arbitrary_characters_in_an_identifier|backquoted identifiers]] to include nearly any character in the identifier, including spaces and punctuation (not newlines or backquote).}}{{Release||6.3| of up to 20 characters. (Analytica ignores any characters beyond the 20th.)  The first character must be a letter. The rest may be letters, digits, or underscore ("_"). An identifier may not include other characters, including space (" ") or accented characters. }} Analytica treats upper and lower case letters as equivalent (i.e., it is case-insensitive). These are examples of legal identifiers: 
  
:<code>a,    Alpha1,{{Release|6.5|| α,}} OOOOO,    B_B_C,    X12345678901,    net_value</code>

See the [[Identifiers Already Used]] for a list of all predefined identifiers. See [[Identifier#Legal_names_for_Identifiers|Legal names for Identifiers]].

==Abbreviations of Identifiers==

Analytica permits abbreviation of identifiers in many, but not all, cases.  You can abbreviate the identifier of an object when you type it at the prompt (">"). If your abbreviation is ambiguous, Analytica will report an error and will not execute the command.  In such cases, you must type the full identifier of the object. For example:

:<code>Fishinapond>sh</code>
:<code>Syntax error:</code> 

:<code>?The Identifier 'Sh' is ambiguous.  Choose one of:</code>
:<code>Show           Showhier       Showkey        Showundef</code>

You cannot abbreviate identifiers of variables or other objects when you put them in the Definition of another object.

==See Also==
* [[Objects and Values]]
* [[Attributes]]
* [[Attrib of Obj]]


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