--- title: "Components of system; advantages, disadvantages" subject: "Simulation and Modeling" chapter: 1 key: "semester_8/simulation_and_modeling:system-components-advantages" source: https://www.bctengineer.com/q/semester_8/simulation_and_modeling/system-components-advantages site: BCT Engineering --- # Components of system; advantages, disadvantages Simulation and Modeling · Chapter 1: Introduction to Simulation - Asked in: 2073 Bhadra, 4+4 marks - Video: [Introduction to Simulation and Modeling](https://www.youtube.com/watch?v=9KdC12vwyqY) — Faisal Concepts - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_8/simulation_and_modeling/system-components-advantages - Whole chapter: https://www.bctengineer.com/md/semester_8/simulation_and_modeling/chapter-1 ## Question Explain the different components of a system with example. Write down the advantages and disadvantages of simulation. ## Short answer A system comprises entities (e.g., customer), attributes (account type), activities (transactions), state variables (queue length), events (arrival), and a boundary. Simulation advantages: testing without disruption, time compression, insight into interactions, handling complexity, cost and safety. Disadvantages: need for expertise, output randomness, development cost, risk of misuse when analytical solutions exist, and reliance on good data. ## Answer #### Components of a system A **system** is a collection of entities (people, machines, etc.) that act and interact together toward the accomplishment of some logical end. The components used when describing a system are: - **Entity:** an object of interest in the system, e.g. a customer in a bank. - **Attribute:** a property of an entity, e.g. the customer's account type or the time of arrival. - **Activity:** a time period of specified length, e.g. a withdrawal transaction taking 3 minutes. - **State:** the collection of variables needed to describe the system at any time, e.g. the number of busy tellers and the number of customers waiting. - **Event:** an instantaneous occurrence that may change the state, e.g. an arrival or a departure. - **Endogenous / exogenous:** endogenous activities and events occur inside the system (service completion); exogenous ones occur in the environment and affect the system (customer arrival). - **Environment and boundary:** everything outside the system that affects it; the boundary separates the system from its environment. **Example (bank):** entities are customers and tellers; attributes are account balance and arrival time; activities are deposit and withdrawal; state is the queue length and number of busy tellers; events are arrival and departure. #### Advantages of simulation - Test new designs/policies without disturbing the real system. - Time compression and expansion. - Insight into variable interactions and system bottlenecks. - Handles complex stochastic systems that have no analytical solution. - Cheap and safe compared with real experimentation. - Useful for training. #### Disadvantages of simulation - Model building needs special training and experience; it is an art. - Results can be hard to interpret because outputs are random; it is difficult to separate system behaviour from randomness. - Modelling and analysis can be costly and time consuming. - It may be used when an analytical solution would be quicker and exact. - A poorly validated model gives misleading results that look convincing. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. In a bank system, the customer's time of arrival is a(n): A. Entity B. Attribute C. Activity D. Event Answer: B. An attribute is a property of an entity; the customer is the entity and arrival time is its property. (Key point: Entity, attribute, activity) 2. Which correctly describes an event? A. A time period of specified length B. The variables describing the system at a time C. An instantaneous occurrence that may change the state D. Everything outside the system boundary Answer: C. An event, such as an arrival or departure, is instantaneous and may change the state; an activity has duration. (Key point: State vs event) 3. Customer arrival at a bank is classified as: A. Endogenous, because it occurs inside the system B. An attribute C. An activity inside the boundary D. Exogenous, because it occurs in the environment and affects the system Answer: D. Exogenous events occur in the environment; endogenous ones, like service completion, occur inside the system. (Key point: Endogenous vs exogenous) 4. Which is a disadvantage of simulation? A. Outputs are random, so results can be hard to interpret B. It cannot handle stochastic systems C. It can never be used for training D. It always gives exact analytical results Answer: A. Random outputs make it difficult to separate system behaviour from randomness; model building also needs skill and can be costly. 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