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Concepts
This section of the documentation covers the use of Objects, Libraries and References, Notations, Styles and Types and how each is created, edited and used in the Sym application.
Objects
An object is the basic building block of all of the symbolic content contained in a document - every term in every symbolic expression in Sym is an instance of an object. Many of the objects used in Sym have an object definition that specifies how the object looks and behaves, but it's also possible to create objects that don't have object definitions. All objects are identified by their name and object names are always defined in a specific namespace. All object definitions contain a type definition. Optionally, objects can also contain Properties, Clauses, Renderings, and a Description.
Property Objects
Command Properties
These properties are designed to be used on object definitions that define commands.

Concepts
This section of the documentation covers the use of Objects, Libraries and References, Notations, Styles and Types and how each is created, edited and used in the Sym application.
- Objects
  An object is the basic building block of all of the symbolic content contained in a document - every term in every symbolic expression in Sym is an instance of an object. Many of the objects used in Sym have an object definition that specifies how the object looks and behaves, but it's also possible to create objects that don't have object definitions. All objects are identified by their name and object names are always defined in a specific namespace. All object definitions contain a type definition. Optionally, objects can also contain Properties, Clauses, Renderings, and a Description.
  - Object Modules
    An Object Module contains object definitions. Object definitions contain the name, type definition, renderings, code and properties that define the functionality of every object. Object Modules are created, edited and managed using the Document Explorer.
  - Creating and Editing Objects
  - Objects Used in Code
    Objects that are commonly used in clauses in function are listed below.
  - Property Objects
    - Object Definition Properties
      These properties are normally used in the definitions of objects that are not either commands or functions.
    - Command Properties
      These properties are designed to be used on object definitions that define commands.
    - Function Properties
      These properties are intended to be used in object definitions that are also functions (have clauses included in the object definition).
  - Special Objects
  - Autogenerated Objects
  - Monoids
    Monoids are typically defined as a binary mapping that has an identity element and is associative. In the construction of the Sym application, we have taken an equivalent, but different approach to defining and handling monoids. It may be surprising to see something so fundamental defined in a non-standard way, so the reasoning for taking this approach is explained below.
- Library Locations and References
  Locations are used to manage groups of libraries and documents. The purpose of locations is to make documents portable from one machine to another. To do that, locations can be online as well as on your local machine. If a document references online libraries, the required libraries will be downloaded automatically when the document is opened.
- Notations and Rendering
  The purpose of notations is to make it possible to easily change the way expressions are displayed. Notations are assigned to Document Modules, Unit Test Modules and Object Modules. The notation assigned determines which renderings are selected for each expression in the module.
- Styles
  Each notation refers to a stylesheet. Stylesheets define Styles. Styles are used in two places. First, they can be used to style text. Second, they can be used to style parts of an expression in a rendering. You can create new style and new stylesheets.
- Types
  Every term in every expression in a Sym document has a type assigned to it. Every object definition has a type definition as one of its components. Since type definitions can include things like type variables, Sym uses a type inferencing process to determine the explicit types assigned to each term in every expression.

Command Properties

These properties are designed to be used on object definitions that define commands.

An object definition defines a command if it is in the Commands namespace and has type Command.


Property	Library	Usage
CommandParameters	Basics	The CommandParameters property determines what expressions are passed into the function that is executed by a command. See Command Parameter Objects for details.
Function	Basics	Defines the function executed by the command.
SetHasChanged	Basics	Some of the commands don't really "change" the document. For example the shift right and left arrow commands only change the highlighting. For these commands, we include the SetHasChanged property with False in the parameter. If this property isn't attached to a command, SetHasChanged will default to True.
ShortcutKey	Basics	Used in object definitions that define commands. Defines the shortcut key for the command. The keystroke can be a Key object, a Keystroke object which takes a key and a modifier as parameters or it can be a Character object.