Glossary

This glossary defines key terms and concepts used throughout the project. This glossary includes both Bixi specific terms and terminology, and also technical terminology used within the context of this project.

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A

Assign

In the real and simulated Bixi networks, to assign a task is to delegate the responsibility of that task to a driver. In the real Bixi network, drivers are not necessarily informed of this assignment as soon as it is made. In the simulated network, drivers are informed of this assignment as soon as it is made.

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D

Diff Frame

A frame that only contains information that has changed between the previous tick and the given tick of a running simulation.

Dispatch

In the real Bixi network, to dispatch a task is to inform a driver of a new task assignment. In the Bixi network simulation, drivers are informed of new task assignments as soon as tasks are assigned, and so the terms "dispatch" and "assign" become interchangeable in this context.

Dispatch delay

In the context of the Bixi network simulation, dispatch delay is the time between the moment at which the user dispatches / assigns a task to a driver on the client side and the moment at which this dispatch is received by backend (and thus by the simulation) and has an actual effect on the behaviour of entities in the simulation.

Dispatcher

A person responsible for assigning / dispatching tasks to drivers.

Dock

A space for a bike to be parked at or retrieved from at a station. Docks do not exist as entities in the context of the Bixi network simulation.

Driver

A Bixi agent that drives a vehicle between stations to service tasks at those stations. Drivers are tracked throughout the simulation travelling between stations to complete battery swap tasks.

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E

Entity

A entity is anything with distinct and independent existence that may be involved in interactions in the Bixi network simulation. Examples of types of entities include drivers, stations, and tasks.

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F

FPS

Stands for "frames per second" and refers to the rate at which the backend / simulation sends frames to the frontend for rendering. Not to be confused with RPS, or "renders per second".

Frame

A Python / JavaScript object containing information on entities in a running simulation at a given point in time (tick). A frame either contains all entity information at a given tick (this is a key frame or only information that has changed between the previous tick and the given tick (this is a diff frame). The use of the word frame alone most likely refers to a diff frame in the context of this project, given that diff frames are more common than key frames.

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I

In Progress

The state of a task when the driver assigned to it is on-route to completing it.

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K

Key Frame

A frame that contains all information at a given tick of a running simulation.

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R

Real time

The amount of time that passes in our reality, which is independent of how much time has passed in a running simulation. Unlike simulation time, the speed at which real seconds or real minutes occur cannot be controlled. The ratio of simulation ticks per unit of real time is not necessarily constant over the duration of a running simulation. This can also be referred to as the wall clock time.

Resource

A resource is a driver-vehicle pair representing a field-agent and their associated vehicle.

Restock

The action of restocking a driver's vehicle on batteries when its inventory is not maxed out.

Route

The path that a driver takes to some location in order to service a task assigned to them. In the context of the Bixi network simulation, each driver may or may not have a route that directs them to the station at which their next task is located.

RPS

Stands for "renders per second" and refers to the rate at which the frontend refreshes the positions of entities on the map. Not to be confused with FPS, or "frames per second", which is the rate at which simulation frames are forwarded to the frontend. The frontend can achieve a higher RPS than the provided FPS by performing intermediate position interpolation.

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S

Scenario

A scenario is the set of initial conditions / behaviour parameters for a simulation. Many (different) simulations can be run from the same scenario.

Service

The state of a task being serviced at its station. When a driver arrives at a task's station, it starts the process of swapping a battery from its vehicle to the low battery e-bike to complete the task. When a task is in this state, it cannot be reordered nor unassigned.

Simulation

A simulation in the context of this project is a series of events that are meant to represent the behaviour of the actual Bixi network. A simulation is either in progress (evolving from the given scenario, and reacting to user input) or completed, in which case a simulation is represented as simply a collection of sequential states of an imitation Bixi network.

Simulation clock time

See simulation time.

Simulation time

The amount of time that passes in a running simulation, which is independent of how much time has passed in our reality. Unlike real time, the speed at which simulation seconds or simulation minutes occur can be controlled. The ratio of simulation ticks per unit of simulation time is necessarily constant over the duration of a running simulation.

Station

In the Bixi network, stations are made up of docks and a terminal. There may or may not be a bike at every dock at a station. In the context of the Bixi network simulation, stations are simply locations at which battery swap tasks may exist - individual docks and terminals don't exist as simulation entities.

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T

Task

In the context of the Bixi network (or simulation of this network), a task is an atomic piece of work that a driver must carry out to support the network.

Task Pop Up

See task spawn.

Task Spawn

In the context of the Bixi network simulation, tasks spawn or "pop up" at a specific station, at a specific tick. A task only exists once it spawns, and thus can only be assigned and affect driver behaviour after it spawns.

Terminal

A machine from which Bixi customers can rent a bike at a station. Terminals do not exist as entities in the context of the Bixi network simulation.

Tick

A discrete unit of time in the Bixi network simulation. The simulation has a distinct (but not necessarily unique) state at each tick, and this state is recorded in a frame.

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V

Vehicle

A means of transportation used by drivers, and carrying an inventory. In the scope of this project, this inventory is limited to batteries for battery swap tasks.

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W

Wall Clock Time

See real time.