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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.
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.

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.
- 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.
  - Creating a New Notation
    Creating a new notation allows you to change the renderings of objects. A notation is assigned to each module (Document modules, Object modules, and Unit test modules). The notation currently assigned to a module is selectable using a combo box in the header of the module.
  - Rendering Expressions
    Rendering expressions are expressions that contain rendering information. They can be created either using the Rendering Editor or by using a function that returns a rendering expression.
  - Rendering Functions
    Renderings can be created in the Rendering Editor, but can also be created using a function. The purpose of a rendering function is to provide a way to generate visual representations of objects that can't be generated using only the renderings that can be created in the Rendering Editor.
- 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.

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.

In Sym, a notation is an object. Like all other objects, notations are defined in Object Modules and have a type definition.

In order for an object to be a valid notation, its object definition must:

Be created in the Notations namespace
Have a type definition of Type: Notation

Object definitions for notations also typically have two properties. The first is a list rendering names that are used in the notation and the second specifies the style sheet that will by used by the notation.

When an expression is rendered, the rendering process will first look to see which notation should be applied. From the notation we can determine which rendering names and styles should be applied. From the rendering names we can find a particular rendering to use for the expression. This is done just by going through the list of rendering names attached to the object definition for the current notation. For each rendering name, we look at the object definition of the expression being rendered to see if there is a rendering with the same rendering name. The first rendering that is found is the rendering that is used for the expression. If no rendering is found in this process, then the default rendering is used.

There are three notations that are predefined, Automatic, Default, and Standard. The Automatic notation plays a special role. A module that is assigned the Automatic notation will use the notation assigned in the Document Options dialog.

In the Default notation, all objects are rendered in the form ObjectName(a, b). So x + y is rendered as Add(x, y) for example.

To assign a notation to a module just select the desired notation from the notations combo box at the top of the module. All of the expressions in the module will be rendered again using the selected notation.

You can also create new notations or change the way expressions are rendered in an existing notation. See Creating a New Notation for more details about creating a new notation and The Rendering Editor for information about creating renderings.