## Language tutorial

This tutorial introduces the CIF language. It explains the general idea behind the concepts of the language, and shows how to use them, all by means of examples. The tutorial is focused on giving a short introduction to CIF, and does not cover all details. It is recommended reading for all CIF users.

### Introduction

CIF is primarily used to create models of physical systems and their controllers, describing their behavior. However, CIF is a general-purpose modeling language, and can be used to model practically anything, ranging from physical real-world systems to abstract mathematical entities.

CIF supports discrete event models, that are mostly concerned with what happens, and in which order. CIF also supports timed systems, where timing plays an explicit role, and hybrid systems, which combine the discrete events with timing. This makes CIF suitable for modeling of all kinds of systems.

The CIF tooling puts a particular focus on supporting the entire development process of controllers. However, just as the CIF language, the CIF tooling can be applied much more generally. The tooling allows among others specification, supervisory controller synthesis, simulation-based validation and visualization, verification, real-time testing, and code generation.

CIF originally stood for Compositional Interchange Format for hybrid systems. As the language has since evolved beyond its original purpose, the name 'CIF' is nowadays only used in its abbreviated form.

### Lessons

Several lessons are available, grouped into the following categories:

- Basics

- Data

- Types and values

- Scalable solutions and reuse (1/2)

- Time

- Channel communication

- Functions

- Scalable solutions and reuse (2/2)

- Stochastics

- SVG visualization and interaction

- Text

- Language extensions

The lessons introduce new concepts, one by one, and are meant to be read in the given order.

Basics

Automata

  Explains automata, locations, events, edges, transitions, and more.

Synchronizing events

  Explains event synchronization, enabledness, traces, and state spaces.

Non-determinism

  Explains multiple causes of non-determinism.

Alphabet

  Explains alphabets for both individual automata and entire specifications.

Event declaration placement

  Explains the placement of event declarations.

Shorter notations

  Explains several shorter notations, including self loops, declaring multiple events with a single declaration, multiple events on an edge, and nameless locations.

Data

Discrete variables

  Explains discrete variables, guards, and updates.

Discrete variable value changes

  Explains how and when discrete variables can change value.

Location/variable duality (1/2)

  Explains the duality between locations and variables using a model of a counter.

Location/variable duality (2/2)

  Explains the duality between locations and variables using a model of a lamp.

Global read, local write

  Explains the concepts of global read and local write.

Monitoring

  Explains monitoring, self loops, and monitor automata.

Old and new values in assignments

  Explains old and new values of variables in assignments, multiple assignments, and the order of assignments.

The `tau` event

  Explains the `tau` event.

Initial values of discrete variables

  Explains initialization of discrete variables, including the use of default values and multiple potential initial values.

Initialization predicates

  Explains initialization in general, and initialization predicates in particular.

Using locations as variables

  Explains the use of locations as variables.

State (exclusion) invariants

  Explains state (exclusion) invariants.

State/event exclusion invariants

  Explains state/event exclusion invariants.

Types and values

Types, values, and expressions

  Explains the concepts of types, values, and expressions, as an introduction for the other lessons in this category.

Values overview

  Provides an overview of the available values, and divides them into categories.

Integers

  Explains integer types, values, and commonly used expressions.

Ranged integers

  Explains ranged integers.

Reals

  Explains real types, values, and commonly used expressions.

Booleans

  Explains boolean types, values, and commonly used expressions.

Strings

  Explains string types, values, and commonly used expressions.

Enumerations

  Explains enumeration types, values, and commonly used expressions.

Tuples

  Explains tuple types, values, and commonly used expressions.

Lists

  Explains list types, values, and commonly used expressions.

Bounded lists and arrays

  Explains bounded lists, arrays, and their relations with regular lists.

Sets

  Explains set types, values, and commonly used expressions.

Dictionaries

  Explains dictionary types, values, and commonly used expressions.

Combining values

  Explains how to combine values of different types.

If and switch expressions

  Explains `if` and `switch` expressions.

Scalable solutions and reuse (1/2)

Constants

  Explains the use of constants.

Algebraic variables

  Explains the use of algebraic variables.

Algebraic variables and equations

  Explains the use of equations to specify values of algebraic variables.

Type declarations

  Explains the use of type declarations.

Time

Timing

  Introduces the concept of timing.

Continuous variables

  Explains the use of continuous variables.

Continuous variables and equations

  Explains the use of equations to specify values of continuous variables.

Equations

  Show the use of equations for both continuous and algebraic variables, by means of an example of a non-linear system.

Variables overview

  Provides an overview of the different kinds of variables in CIF, and their main differences.

Urgency

  Explains the concept of urgency, as well as the different forms of urgency.

Deadlock and livelock

  Explains the concepts of deadlock and livelock.

Channel communication

Channels

  Explains point-to-point channels and data communication.

Dataless channels

  Explains `void` channels that do not communicate any data.

Combining channel communication with event synchronization

  Explains how channel communication can be combined with event synchronization, further restricting the communication.

Functions

Functions

  Introduces functions, and explains the different kind of functions.

Internal user-defined functions

  Explains internal user-defined functions.

Function statements

  Explains the different statements that can be used in internal user-defined functions.

Functions as values

  Explains using functions as values, allowing functions to be passed around.

Scalable solutions and reuse (2/2)

Automaton definition/instantiation

  Explains using automaton definition and instantiation for reuse.

Parametrized automaton definitions

  Explains parametrized automaton definitions.

Automaton definition parameters

  Explains the different kinds of parameters of automaton definitions.

Groups

  Explains hierarchical structuring using groups.

Group definitions

  Explains groups definitions and parametrized group definitions.

Imports

  Explains splitting CIF specifications over multiple files using imports.

Imports and libraries

  Explains how to create libraries that can be used by multiple CIF specifications using imports, as well as how to use imports to include CIF specifications from other directories.

Imports and groups

  Explains how imports and groups interact.

Namespaces

  Explains namespaces, and how they can be used together with imports.

Input variables

  Explains input variables, how they can be used for coupling with other models and systems, and their relation to imports.

Stochastics

Stochastics

  Introduction to stochastic distributions, which allow for sampling, making it possible to produce random values.

Discrete, continuous, and constant distributions

  Explains the different categories of stochastic distributions: discrete, continuous, and constant distributions.

Pseudo-randomness

  Explains how computers implement stochastics using pseudo-random number generators, and how this affects the use of stochastics in CIF.

SVG visualization and interaction

SVG visualization

  Introduction to SVG visualization, which allows to connect an image to a CIF model and update the image based on the state of the model.

First example

  A first simple example of SVG visualization.

Inkscape

  Explains how to use the Inkscape drawing program to edit SVG images.

Sun/moon example

  An example of using groups of SVG objects, as well as controlling the visibility of objects based on the current locations of automata.

Walk example

  An example of using groups of SVG objects, positioning them, and changing their position using an output mapping, as well as using the `scale` standard library function, text formatting, multiple values in an output mapping, and multiple format specifiers in a format pattern.

Rate example

  An example of using literal values in output mappings, as well using simple solution to solve visualization problems.

Workstation example

  An example of fixed-value and clock-based object widths, changing the fill color of objects, updating multiple attributes of an SVG object, specifying colors in SVG, and improving scalability by reusing mappings.

Tank example

  An example of using the `scale` standard library function, as well as how inverting the y-axis can reduce the number of output mappings.

Lamps example

  An example of hierarchical scalability of SVG images by reusing mappings, as well as copying elements and moving them to the desired position.

Buffers/products example

  Another example of hierarchical scalability of SVG images by reusing mappings, as well as copying (copied) elements and moving them to the desired position.

SVG interaction

  Explains how to extend a model to couple it to an image for interaction via a visualization.

Text

Print output

  Introduces print output by means of print declarations, which allows to print custom text from the model at runtime, either to the console or to a file.

Print output examples

  Explains print output by means of examples.

Text formatting

  Explains text formatting by means of examples.

Language extensions

Supervisory controller synthesis

  Explains how to extend a model to make it suitable for supervisory controller synthesis.

Annotations

  Explains how to annotate elements of the specification with extra information.