Lecture 10: Specifying systems - intro. The main contents of this chapter include all of the following: Domains, phenomena; states, events; context diagrams; systems and system descriptions; basic formalisms for specifications. | Ivan Marsic Rutgers University LECTURE 10: Specifying Systems - Intro Topics Domains, Phenomena States, Events Context Diagrams Systems and System Descriptions Basic Formalisms for Specifications Boolean Logic Finite State Machines World, Parts, Phenomena Example of a Problem Domains Example of Problem Domains Example of Problem Domains Software-to-be (1) Tenant (4) List of valid keys (3) Lock (6) Photosensor (7) Light (8) Alarm bell (9) Desktop computer (2) Landlord (3) Key (5) Device preferences (10) Tenant accounts (11) Log of accesses Definitions A phenomenon is a fact, or object, or occurrence that appears or is perceived to exist An event is an individual happening, occurring at a particular point in time Events are indivisible and instantaneous A state is a relation among individual entities and values, which can change over time Individuals are in relation if they share a certain characteristic RelationName(Individual1, , . | Ivan Marsic Rutgers University LECTURE 10: Specifying Systems - Intro Topics Domains, Phenomena States, Events Context Diagrams Systems and System Descriptions Basic Formalisms for Specifications Boolean Logic Finite State Machines World, Parts, Phenomena Example of a Problem Domains Example of Problem Domains Example of Problem Domains Software-to-be (1) Tenant (4) List of valid keys (3) Lock (6) Photosensor (7) Light (8) Alarm bell (9) Desktop computer (2) Landlord (3) Key (5) Device preferences (10) Tenant accounts (11) Log of accesses Definitions A phenomenon is a fact, or object, or occurrence that appears or is perceived to exist An event is an individual happening, occurring at a particular point in time Events are indivisible and instantaneous A state is a relation among individual entities and values, which can change over time Individuals are in relation if they share a certain characteristic RelationName(Individual1, , Individualn) Events Events take place at transitions between the states Relations: Examples Relation: Neighbors (Person_i, Person_j) Relation: Sandwich (Bread-slice, Ham-slice, Bread-slice) Example: States of a DVD Player State 1: NotPowered (the player is not powered up) State 2: Powered (the player is powered up) State 3: Loaded (a disc is in the tray) State 4: Playing State 1: NotPoweredEmpty (the player is not powered up and contains no disc) State 2: NotPoweredLoaded (the player is not powered up and a disc is in the tray) State 3: PoweredEmpty (the player is powered up and contains no disc) State 4: PoweredLoaded (the player is powered up and a disc is in the tray) State 5: Playing Different Abstractions DVD player Power button Play button Disc tray DVD player Atomic object Object composed of parts (Level of detail) Example: States of a DVD Player System Part (Object) State Relations Power button {Off, On} Disc tray {Empty, Loaded} Play .
