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Distributed Embedded Systems, Fall 2000 PhD Project Report
Lu Luo December 2000
A UML documentation for an elevator system
Lu Luo
A UML documentation for an elevator system
1. Introduction
This paper is a PhD project report for the course Distributed Embedded Systems at Carnegie Mellon University. Throughout this course, a distributed real-time system – an elevator control system– is specified, designed, built, and simulated. Object Oriented Analysis and Design methods, in specific the Unified Modeling Language (UML) are used when designing the system. A lot of corners in the design of this elevator system are cut in the regular class. The existing UML documentations for the elevator lab of this course are pretty lame compared to real elevators. It is therefore not so clear whether UML will really represent the design of an elevator well. In this report, a rigorous UML documentation package for the class project is given, based on current system design. From different points of view how UML can be used in a real-time, distributed system, three groups of UML diagrams are given, the diagrams in these groups differ mostly in their class diagrams, focusing on the viewpoint of object architecture, software architecture and system architecture correspondingly. In the following part of this report, overviews of UML and distributed embedded systems are given in section 2 and section 3, correspondingly. In section 4, the design of our elevator control system is presented from a static structural point of view, i.e. the Use Case diagram and the Class diagrams are presented and analyzed. The Sequence diagrams and State Chart diagrams given in Section 5 emphasize on the dynamic aspects of the system. Section 6 is the conclusion.
2. A Brief Introduction to UML
The Unified Modeling Language (UML) is the industry-standard language for specifying, visualizing, constructing, and documenting the artifacts of software systems, as well as other nonsoftware systems. UML simplifies the complex process of software design, making a "blueprint" for construction, and is now the standard notation for software architecture. UML provides both the structural views and behavioral views of the system. A set of diagrams with different graphical elements is the core part as well as the most expressive presentation in UML. The UML includes nine kinds of diagrams, for the sake of grasp the most representative aspects of the design of elevator system, in this paper only following UML diagrams are used and analyzed: Use Case diagram shows a set of use cases and actors (a special kind of class) and their relationships. Use case diagrams address the static use case view of a system, these diagrams are important in organizing and modeling the behaviors of a system.
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interact with the system. the definitions of real time system. only the sequence diagrams are given in this report. Use cases allow the designers to describe the way in which humans and external devices.A UML documentation for an elevator system Lu Luo Class diagram shows a set of classes. 2 of 29 . but there are clear bounds within which these must be completed. so not only do we have to perform the correct functions. and Embedded Before discussing the detailed problems involved in designing our elevator system with UML. Sequence diagram is an interaction diagram. and Deployment diagram showing the configuration of run-time processing nodes and the components that live on them. the difference between real-time distributed systems and software systems in the common sense that most object-oriented design and analysis pays effort on by UML are briefly stated. and embedded system are necessary to be presented here. Class diagrams are the most common diagrams used in modeling object-oriented systems. a special kind of State chart dia gram showing the flow from activity to activity within a system. consisting of states. As one of the object-oriented techniques. the events which cause the interaction and the detailed system response. The rest four kinds of UML diagrams are: Object diagram. distributed system. An embedded computer system is a system that uses a computer as a component. Activity diagram. and can be transformed from one into the other. the other interaction diagram in UML is the Collaboration diagram. Interaction diagrams address the dynamic view of a system. An Over view at Systems that are Real-time. State chart diagrams address the dynamic view of a system. Sequence diagram emphasizes the time ordering of messages between objects in the system. but whose prime function is not that of a computer. UML is basically suitable for real time system development. Since either of them contributes to the same extend of understanding of our system. in real time systems. describe for a given use case. including timing. class. events and activities. showing a set of objects and their relationships. According to Kopetz. the pros and cons of UML used in designing distributed embedded systems are largely discussed. but also on the physical instant at which these results are produced[1]. a real time computer system is a computer system in which the correctness of the system behavior depends not only on the logical results of the computations. and collaborations and their relationships. which is essential for real time systems. State chart diagram shows a state machine. Class diagrams address the static design view of a system. Component diagram. As the saying goes: "The right answer late is wrong". performance requirements are as important as functional requirements. while sequence diagrams give more ideas of time. Object sequence diagrams. Sequence diagrams and collaboration diagrams are isomorphic. In the rest parts of this paper. transitions. interfaces. State chart diagrams are especially important in modeling the behavior of an interface. Distributed. 3. or collaboration and emphasize the event-ordered behavior of an object. which is especially useful in modeling reactive systems. besides sequence diagram. showing the organizations and dependencies among a set of components. while collaboration diagram emphasizes the structural organization of the objects that send and receive messages. There are techniques within UML definition that are a natural fit for specifying and designing real-time systems.
Modeling the network. such as moving up and down. When the car stops at a floor. task and hardware levels. The car moves fast between floors. or a class. Specifying the time constraints at the object. We've been trying to answer the question during our practice using UML to design the elevator system: "Is UML a suitable modeling language for the development of real-time systems?" We found that based on the features mentioned in last paragraph. open and close doors. A use case diagram models the dynamic design view of systems. These techniques are good enough to capture usage scenarios and identify likely time problems. that a system performs to yield an observable result of value to an actor [2]. For every floor except for the top floor and the lobby. and association relationships 3 of 29 . and both human and actors expect the system to behave in predictable ways. a subsystem. 4. a use case models the behaviors of a system or a part of a system. but it should be able to slow down early enough to stop at a desired floor. The elevator is supposed to be used in a building having floors numbered from 1 to MaxFloor. as follows: • • • The definition of specific hardware elements and their characteristics. and of course. UML is applicable but not yet enough. pick up passengers. In the following sections. including variants. Use case diagrams are central to modeling the behavior of a system. Our elevator has the basic function that all elevator systems have. The main contents of a use case diagram are: • • • Use Cases Actors Dependency. and is a description of a set of sequences of actions. emergency brake will be triggered and the car will be forced to stop under any unsafe conditions. Modeling the static aspects of the system 4. There are some main challenges in the design of real-time embedded system with UML. where the first floor is the lobby.1 A snapshot of the elevator control system The elevator system designed as our class project is rather an "ideal" elevator in which some of the technical corners are cut. There are car call buttons in the car corresponding to each floor. there are two hall call buttons for the passengers to call for going up and down. In order to certificate system safety. generalization. we will attempt to figure out how to use UML for a better description for the elevator system. In UML. Use case diagram shows a set of use cases and actors and their relationships.A UML documentation for an elevator system Lu Luo Class diagrams helps to separate system components and define interfaces between them. Some practical suggestions that might be a useful addition to the standard UML are given out.2 Use Case Diagram All systems interact with human or automated actors that use the system for some purpose. 4. the doors are opened and the car lantern indicating the current direction the car is going is illuminated so that the passengers can get to know the current moving direction of the car. There is only one down hall call button at the top floor and one up hall call button in the lobby.
turns on or turns off the light of car call buttons.A UML documentation for an elevator system Lu Luo According to the requirements document in our class. Indicating Car Position: Similarly. how to make the decision of stop. Trigger Emergency Brake: There is safety mechanism within the car to make sure that an unsafe state is not transiently generated. which will be described in detail in later sections of this paper. as shown in Figure 1: • Process Car Calls: This use case includes several scenarios. The passenger interacts with the Elevator system by making car calls 4 of 29 . Process Hall Calls: Similar to Car Call processing. and driving directions of the car. etc. etc. Move/Stop the Car: The main function of an elevator. updates the record of car calls stored in system controlling parts. These scenarios includes that the elevator receives car calls from the passengers. detailed action will include the changing of driving speed. Indicating Moving Direction: The elevator should have this mechanism to let the passengers know the current moving direction of the car such that the passenger might decide whether to enter the car or not. which is the role that humans play when interacting with the system. The functional areas of this use case should also enable the passengers to make door reversals when the doors are closing and the passenger wants to get in the car. the use case diagram of elevator systems is showed in Figure 1: Elevator Process Car Calls Move/Stop the Car Open/Close the Doors Passenger Indicate Moving Direction Trigger Emergency Brake Process Hall Calls Indicate Car Position Figure 1: Use Case Diagram of Elevator System There are seven use cases based on the requirement documentation of the elevator system in our class. • • • • • • The only actor in elevator system is the passenger. Open/Close the Doors: The elevator should be able to open and close the doors for the passengers to get in and out of the car. updates the record of hall calls in system controlling parts. this use case includes that the elevator receives hall calls from the passengers. the elevator should let the passengers know whether his/her destination floor is reached so that the passenger may decide to leave the car. turns on or turns off the light of hall call buttons.
the ElevatorControl – command the doors to open and close. we build this class diagram from the view of object composition of the system. The static view mainly supports the functional requirements of a system – the services the system should provide to the end users. and detail aspects such as the attributes and operations within a class as well. generalization. three groups of class diagrams are presented and analyzed in detail. We can now get some idea of how the system is composed of from the description of classes in Figure 2. such as the system architecture. The most common contents of a class diagram are: • • • • • Classes Interfaces Collaborations Dependency.4. which is out of the scope of our current view. • • ElevatorControl: The central controlling object in the elevator system. one of the most commonly used diagrams in object-oriented system. 4.2 and according to the requirements of the system. models the static design view for a system. The passenger also makes decision whether to enter/leave the car or not by observing the indication of moving direction and car position. In this regard. We will not go any further into the detailed class components such as attributes and operations of each class. intuitively we get a class diagram as is shown in Figure 2.3.1 Class Diagram – the Object Construction View From the elevator use cases we've got in section 4. 4. and collaborations and their relationships. The corresponding sequence diagrams for each class diagram is introduced in section 4. and Indicate Car Position. A class diagram shows a set of classes. and association relationships Notes and constraints In the following subsections. Class diagrams involve global system description. Indicate Moving Direction. Process Hall calls. the "god" object . Door: There are two doors in the system. interfaces. Therefore the use case diagram shows that the actor has relationship with four use cases of the system: Process Car Calls. The discussion on different views of class diagrams for the system will be put into emphasis later in this paper.3 Class Diagram Class diagram. We will see from our practical experience that lots of fun comes out when modeling out system with class diagrams. 5 of 29 .A UML documentation for an elevator system Lu Luo and hall calls. ElevatorControl communicates and controls all other objects in the system. according to the situation stated in the use case.
Safety: Whenever an emergency happens according to the definition of emergency brake trigger in the requirement documentation. Indicator: There are two kinds of indicators in the system.e. which further generalizes two subclasses CarCallButton and HallCallButton. this class diagram helps understanding the basic design idea of the system. and the control class ElevatorControl. to make stops at floors when necessary. When we tried to go further into the design of our elevator control system. All the classes have interfaces with the central controller.the Object Construction View • • • • Car: The car is being controlled to move up and down (in different speeds). In the context of this report. i. The reason why we know that the class diagram is not quite perfect for a final design before we really meet difficulties MIGHT because of above reasons. whose job is in charge of the actions of other objects. we "inherit" a ready elevator system architecture from the instructor. the order of designing the system with an existing architecture and capturing the UML documentation is reversed. rather than designing the system first using UML. for the passenger to know the position and direction of the elevator. we have the Button classes. and thus find our way toward a detaile d design then a good implementation of our system starting from this class diagram. and have part of the software design in hand before working on the UML. the CarLantern). Button: The ElevatorControl class also controls the button class. we also have the Safety class fulfilling the system need of emergency brake processing. we have Indicator class.A UML documentation for an elevator system Lu Luo Door 2 1 ElevatorControl 1 1 Car control 1 1 1 control Button * * Indicator communicate & control control 1 CarCallButton HallCallButton Safety control CarPositionIndicator CarLantern Figure 2: Class Diagram . The indicators are controlled to show the information about the current position and moving direction of the car. but it is almost certain in other cases that the 6 of 29 . the CarPositionIndicator and the CarDirectionIndicator (i. From the point of view of object division and system functioning. get the information whether a button is pressed and in turn controls the illumination of Button lights. for the passenger to make car calls or hall calls.e. we have the class Door.2. we have the class Car. for opening or closing the doors. The classes captured in this diagram can cover all the functional aspects of the system: for moving or stoppin g the car. the ElevatorControl commands the Safety This version of class diagram is derived directly from the use cases stated in section 4. The control object communicates with the Button objects. problems arose.
each controls a CarLantern indicating the current moving direction of the car.2 Class Diagram – the Software Architecture View Based on the analysis of last section and based on the software architecture from the class project. i. it is inevitable that these objects compete for the limited computing resources of the controller. central node controlling is still not an efficient solution for a distributed system like the elevator. DriveControl controls the elevator Drive . Considering the current class diagram in hand. • • • DoorControl controls the action of DoorMotor. The control objects share (some of) the property of ElevatorControl. all other control objects are derived from the super class ElevatorControl. some of the other objects. Low efficiency for the whole system: Even if the computing resources in the controller are fast/large enough such that every control need is processed and taken into action in time. Competing for computing resource: When more than one object want to get controlled by the central object at the same time. or make a door reversal. the software design is going to be a failure. Except for Dispatcher. The objects controlled by the control objects are defined as environmental objects. However. each of the two DoorMotors on a car is controlled by a DoorControl object. sooner or later. which is simulated and proved to be practically suitable of being the control system for an elevator. a class diagram is derived from this point of view. which although exist in the elevator system. they are outside the scope of the software system. the "hardware". LanternControl are in the number of two.e. 7 of 29 . as objects like the Door and the Car are actually part of the system. • • 4. All the computing and controlling tasks have to be done within this object Idleness of some other objects: While the ElevatorControl keeps working all the time. If a better solution is not found. Provided our system under discussion is a normal centralized system where every component (software and/or hardware) is controlled by one processor. even worse. The software architecture of the actual elevator control system is reflected accurately in this diagram. our current class diagram solution may not cause future design defects. such as Button and Indicator only act as system interface. the nature of being a distributed embedded system determines that the class diagram merely from the point of view of objects in the elevator system is not adequate. and some of the objects may not get timely control messages for it to keep normal operation. are in fact not belong to the software control system. and stopping at floors when necessary.A UML documentation for an elevator system Lu Luo designers will find this the inappropriateness of this design for future development stages. from the point of view of control software. In next section we will discuss these noncontrol objects in detail from the system architecture point of view. potential defects of our future software design are stated as following. • • Overburden of the central object: From above analysis we can see that the ElevatorControl object has to act as the central controller that interacts with all other objects. DoorMotor can be commanded to open.3. This class diagram provides the solution for how to design and implement the control software. and has its own attributes and operations used for the object it controlled. close. which will cause a fatal defect in realtime system. which acts as the main motor moving the car up and down.
the safety actions vary if the • 8 of 29 .the Software Architecture View There are two non-control objects in the system: • Dispatcher does not control actual elevator components. The Dispatcher interacts with nearly all the control objects in the system except for LanternControl. where one controls the Up HallCallButton and the other Down. EmergencyBrake 1 1 Safety 1 1 ElevatorControl 1 1 Dispatcher control 1 communicate 1 * 1 * LanternControl * CarPositionControl DoorControl DriveControl ButtonControl 1 control 1 DoorMotor control 1 1 1 control 1 1 1 control 1 CarPositionIndicator Drive Lantern * HallButtonControl * CarButtonControl control 1 1 HallButton 1 1 CarButton control Figure 3: Class Diagram . There is one Dispatcher for each car.A UML documentation for an elevator system • • • Lu Luo HallButtonControl exists in pair on each floor. Safety is also an environmental object. CarPositionIndicator gives value to the CarPositionIndicator so that the passengers might know the current position of the car. but it is important in the software system. CarButtonControl is one for each floor and all locate in the car. which does not belong to the control software but is an important part of the system. whose main function is to calculate the target moving direction and destination for the car. as well as to maintain the opening time for the doors. In the real world. The HallButtonControl accepts hall call button presses controls as well as gives feedback to hall call lights. The CarButtonControl accepts CarCallButton calls and is in charge of turning on/off the corresponding car call lights.
though. DoorControl. But as the class diagram is an excellent way of describing the static structural aspects of a system. From the system architecture view. as following: • • • How do the control objects control the environmental objects? How does one object get necessary information from other objects? How to model the network? From the view of the system architecture. the class diagram is further detailed with classes as the network and sensors/actuators added to model the actual system architecture. starting from this class diagram issues about the implementation detail of our system will still arise. as follows: Control Objects • We have stated a lot on the control objects in our system in previous sections. In our system. the passenger object is not shown (unlike other environmental objects) in Figure 3. Passengers interact with hall call buttons and car call buttons. Control objects controlling an system entity (such as the Doors and the Buttons) are connected to sensors and actuators. no one is overburden or idle. 4. in our elevator simulation system. However. only some message is displayed. observe the direction and position of elevator. Network is the 9 of 29 . There is no need competing for the computing resources of the central controller since the controllers are devoted to their controlled objects.A UML documentation for an elevator system Lu Luo emergency brake of an elevator is triggered. CarButtonControl. getting messages from sensors and send feedback to actuators to perform the control function. in this view of the system. Strictly. For the sake of simplicity.3 Class Diagram – the System Architecture View For answering the question brought out in last section. HallButtonControl and Dispatcher. make door reversals. the class diagram does not contain exactly the same meaning as in normal UML class diagrams. if an emergency brake is triggered. these questions will be answered. The software view of class diagram solved most of the problems put forward in last section.3. All the control objects connect to the network. the control objects including CarPositionControl. Since the control tasks are distributed to several control objects. etc. getting input messages from the network. which is modeled as the network class in the middle of the diagram. passenger is also modeled as an environmental object. • • Network • All the control objects are connected with the communication network. DriveControl. LanternControl. and sending output messages to the network for other objects to use. why not use it to help express better the system architecture? The components in the class diagram shown by Figure 4 can be sorted into eight categories. each controlling one or a couple of environmental objects.
DoorReversal. and DriveSpeed. HallCall.A UML documentation for an elevator system Lu Luo Car CarPositionIndicator CarPositionControl CarLantern CarCall CarLight CarButtonControl LanternControl Dispatcher Dispatcher Network 1 Floor HallCall HallButtonControl HallLight 2 AtFloor Door DoorOpen 1 DoorReversal DoorControl DoorPosition DoorClose DoorMotor 1 Drive DriveSpeed DoorMotor HoistwayLimit 1 DriveControl Drive CarPosition Safety Safety 2 Drive 1 EmergencyBrake 2 Figure 4: Class Diagram . DoorClosed. DoorOpen.the System Architecture View System Sensors • • System values are available for use by the control system. The system sensors in the class diagram include AtFloor. 10 of 29 . On the class diagram the system sensors are connected with the control objects with an arrow pointing to the control objects. CarCall.
Door. The environmental objects are accessible to the control system indirectly via manipulation of actuators. we can make a comparison of Figure 5 and Figure 2. • Grouped objects • • • Grouped objects are Car. Having a look at the very beginning. all system sensors are connected to their control objects via physical network interface. and Drive. CarPositionIndicator. Instead of having one central object taking care of every control task in the system. The cla ss diagram as we got in Figure 5 is an evolution of the original one. each with a dashed box surrounded. HallLight. Floor. and DoorMotor illustrated in the class diagram with shadow are environmental objects. each (group of) object has it own functional area and communicate and collaborate with other objects in the system.A UML documentation for an elevator system • Lu Luo Except for AtFloor. CarLight. the control objects get the message from both the sensors and the network to give out correct control messages. They are illustrated with a dashed arrow line connected to the control objects. but used in the simulation. Dispatcher. CarLantern. We find that the object structure showed in Figure 5 is improved towards a more distributed system. as implicated in Figure 2. 11 of 29 . Environmental objects • The Safety. System Actuators • • System actuators on the class diagram are connected with the control objects with an arrow pointing from the control objects. The relationship of grouped objects in the system architecture is illustrated in Figure 5. It is connected to the Safety object with dashed arrow line. Drive. Drive. The system actuators in the class diagram include DoorMotor. DoorPosition and CarPosition in the system. Environment-only Sensors • • There are two environment-only sensors. Environme nt-only Actuators • The EmergencyBrake is the environment-only actuator in the diagram. and Safety. Environment-only sensors are pseudo-sensors and are not accessible to the control system. with the environmental class "Passenger" added to.
most of the future design of the software can be figured out. the class diagram describes a solution to the problem as the object architecture. three different class diagrams emphasizing on different views of the elevator system are given in an evolutionary way. and gives a skeletal describing for the system. it is very important to know in distributed embedded systems how the system components are working together. individually. Objects that share the same responsibilities are generalized into a class. The class diagram generated from this view grasps the main functional area of the system design. each represents just one aspect. The software design is captured by describing a collection of objects communicating and collaborating to implement a specific function.3. Each of the three views captures one aspect of the system. Objects communicate by sending messages to each other. From the view of object construction. and gives an overall understanding of the system design when combined together. 12 of 29 .the Revised Object Construction View 4. every class diagram is just a graphical presentation of the static design view of a system. Collectively. Compared to normal software systems. all the class diagrams of a system represent the system's complete static design view. Based on the class diagram derived from this view.4 The Static Structure – Brief Summary In section 4. The system architecture view provides the most complicated yet the most delicate description of not only the software. much more design and implementation details are captured. but also the structure of the whole system. From the view of software architecture . No single class diagram can capture everything about a system's design view.A UML documentation for an elevator system Lu Luo 2 Door 2 1 Car 1 * Passenger 2 1 Safety 1 1 1 1 Drive * * Floor 1 * 1 Dispatcher 1 1 Figure 5: Class Diagram . After all.
which shows an interaction among a set of objects and their relationships (another kind of interaction diagram is collaboration diagram). the other is vice versa. The purpose of the Sequence diagram is to document the sequence of messages among objects in a time based view. some experiential methods are given on how to migrate from the requirement to design. the only difference is the driving time before the passenger could get on. UML provides Sequence diagrams and Collaboration diagrams. 13 of 29 . only the Sequence diagrams for the elevator system are given. The state diagrams commonly contain: • Objects • Links • Messages • Respond Time (especially useful in real-time systems) The vertical "lifelines" represents objects of interest.A UML documentation for an elevator system Lu Luo 5. where many technical details obstruct a quick understanding of interaction among objects. based on the class project design of this semester. the collaboration diagrams can be derived from the sequence diagrams without too much effort. the (x sec) in the diagram reflects the travel time of the elevator. i. In the context of this paper.e. one scenario is that the elevator is moving the same direction as the passenger's destination. Modeling the dynamic aspects of the system To model the dynamic aspects of a system. 5. the objects in sequence diagrams are based on the class diagram from the software architecture view. one per use case scenario.1. From our design practice. There may be multiple sequence diagrams per use case. since some of the messages are coming out from the passengers.1 Sequence Diagram Sequence diagram is one kind of interaction diagrams. UML supports the notation of respond time in the sequence diagrams. nor go too further in the system architecture view. Scenario 1. In some sequence diagrams the passenger appear to be an object of the system. State chart diagrams for the elevator system are also given in this section. Time flows from top to bottom. The reason for doing that is we want to neither stay in the object construction view. The scope of a typical sequence diagram includes all the message interactions for (part-of) a single use case.1 Use Case 1 – Process hall calls There are two scenarios for this use case: when the passenger requests a hall call service by pressing hall call button(s). which makes it feasible to specify the performance requirements for a real time system.1 Hall Call service – the elevator is moving towards the same direction as the passenger's destination. in which the functions of objects are obscure and inadequate. Messages are shown flowing between object lifelines. In following sections. 5. The two scenarios can share the same sequence diagram.
A UML documentation for an elevator system Lu Luo Scenario 1. Again.2 Hall Call service – the elevator is moving towards the opposite direction as the passenger's destination.2 Car Call service – the elevator is moving towards the opposite direction as the passenger's destination. Scenario 2.1&1.Hall Call Service 5.2 Use Case 2 – Process car calls There are two scenarios for this use case: the passenger enters the car. the passenger will either get to the destination floor when the elevator passes by it. or when the elevator turns around. the two scenarios can share the Scenario 2.1 Car Call service – the elevator is moving towards the same direction as the passenger's destination. Passenger HallButton press() HallButtonControl Dispatcher DriveControl Drive DoorControl Door HallCall() TurnOn() Update() DesiredFloor() Move() AtFloor() Stop() AtFloor() TurnOff() DesiredDwell() Close() AtFloor() Open() (x sec) Figure 6: Scenario 1. presses a car call button.1. 14 of 29 . depending on the current moving direction of the elevator.2 . The passenger may either want to go to a upper floor or a lower one.
Within a safe scope.1&3. and Scenario 3.1. Scenario 3.2 .Car Call Service 5.A UML documentation for an elevator system Lu Luo Passenger press() CarButton CarButtonControl Dispatcher DriveControl Drive DoorControl Door CarCall() TurnOn() Update() DesiredFloor() Move() AtFloor() Stop() AtFloor() TurnOff() DesiredDwell() Close() AtFloor() Open() (x sec) Figure 7: Scenario 2.3 Use Case 3 – Move/Stop the car There are two scenarios for this use case: Scenario 3.2 Move the car – the elevator is commanded to start moving from stop status.2 for moving Down. The moving direction and desired floor of the car are given by the Dispatcher.1 is for moving Up. 15 of 29 .1&2. the car should move from slow speed to a fast speed.
4 .Up/Down() Drive AtFloor .Moving the Car from Stop to Slow then to Fast Scenario 3.1.3&3. which can share one sequence diagram: 16 of 29 . DriveControl MoveFast .A UML documentation for an elevator system Lu Luo Dispatcher Door DriveControl Stop() Drive Closed() Closed() DesiredDirection() DesiredFloor() MoveSlow .Down/Up() MoveSlow .Moving the Car from Fast to Slow then to Stop 5. it should be commanded to slow down its drive speed.1&3.2 . and at last stop at the floor.Up/Down() MoveFast-Up/Down() Figure 8: Scenario 3.Up/Down() Stop() Figure 9: Scenario 3.3&3.4 Stop the car – when the elevator is approaching the desired floor.4 Use Case 4 – Indicate car position There are two scenarios for this use case.
Indicating the Car Position 5. the DOWN CarLantern is illuminated. Scenario 4. the CarPositionIndicator should be commanded to indicate the desired floor.A UML documentation for an elevator system Lu Luo Scenario 4.2 . the CarPositionIndicator should be commanded to illuminate to indicate the current car position.CurrentFloor() Closed() DesiredFloor() Indicate . 17 of 29 .1 Indicating moving direction (up) – When the doors of the elevator are open and the desired direction of the car is UP. the UP CarLantern is illuminated.1&4. Scenario 5.DesiredFloor() Figure 10: Scenario 4. When the doors are closed. the CarLantern is turned off. the CarLantern is turned off. Door DoorControl AtFloor() Open() Drive CarPositionControl AtFloor() CarPositionIndicator Dispatcher DesiredDwell() DoorOpened() CurrentFloor() Close() Indicate . which can share one sequence diagram: Scenario 5.2 Finish indicating car position – when the doors are closed.1 Indicating car position – whenever the doors of the elevator are open.1.5 Use Case 5 – Indicate moving direction There are two scenarios for this use case.2 Indicating moving direction (down) – When the doors of the elevator are open and the desired direction of the car is DOWN. When the doors are closed.
1&5.2 .6 Use Case 6 – Open/Close the doors There are three scenarios for this use case: Scenario 6.1. the doors should open for a period of time (DesiredDwell).1 Open the doors – When the car stops at a floor. 18 of 29 . so that the passengers may get in the car. the doors should close so that the car can move to the next destination. Scenario 6.A UML documentation for an elevator system Lu Luo Door DoorControl AtFloor() Open() Drive LanternControl AtFloor() CarLantern Dispatcher DesiredDwell() DoorOpened() CurrentDirection() Close() Turn On() Closed() Turn Off() Figure 11: Scenario 5.Indicating the Moving Direction 5.2 Close the doors – After opening for a specific period of time (Desiredperiod).
2 .A UML documentation for an elevator system Lu Luo Dispatcher AtFloor() Drive AtFloor() DoorControl Door DesiredDwell() Open() DoorOpened() Close() DoorClosed() Figure 12: Scenario 6. if there are passengers who want to get into the car.3 .3 Door reversals – When the doors are closing but not fully closed.Door Reversal 19 of 29 .1&6. Passenger Dispatcher DoorControl Close() Door DoorReversal() StopClosing() Open() DesiredDwell() Close() DoorClosed() DoorClosed() Figure 13: Scenario 6. the doors should open again for another period of time. then close again.Open and Close the doors Scenario 6.
A UML documentation for an elevator system Lu Luo 5. the emergency brake will be triggered.7 Use Case 7 – Trigger emergency brake There are five scenarios for this use case: Scenario 7.Emergency Brake .The car won't move 20 of 29 . Dispatcher DriveControl Drive Safety EmergencyBrake DesiredFloor() Move() AtFloor() Stop() Not Stopped() Emergency Brake() Figure 14: Scenario 7.2 .Emergency Brake .1 .2 Emergency Brake 2 – If the car is commanded to move but it does not move. DriveControl Move() Drive Safety EmergencyBrake Not Moving() Emergency Brake() Figure 15: Scenario 7. the emergency brake will be triggered.1 Emergency Brake 1 – If the car is commanded to stop but it won't stop at a desired floor.1.The car won't stop at desired Floor Scenario 7.
4 .3 Emergency Brake 3 – If the doors are commanded to open when the car stops at a floor. but the doors won't open. DriveControl Drive DoorControl Close() Door Safety EmergencyBrake DoorClosed() Move() DoorOpened() Emergency Brake() Figure 17: Scenario 7. Dispatcher DriveControl Drive DoorControl Door Safety EmergencyBrake DesiredFloor() Move() AtFloor() Stop() AtFloor() Open() Cannot Open() Emergency Brake() Figure 16: Scenario 7. the emergency brake will be triggered.Emergency Brake .4 Emergency Brake 4 – If the doors open when the car is moving.The doors won't open when the elevator stops at desired floor Scenario 7.A UML documentation for an elevator system Lu Luo Scenario 7.The doors open when the elevator is moving 21 of 29 .Emergency Brake .3 . the emergency brake will be triggered.
DriveControl Drive Safety EmergencyBrake Move() Reach Hoistway Limit() EmergencyBrake() Figure 18: Scenario 7.Emergency Brake .5 . Usually the state machine in a state chart models the behavior of a reactive object. These methods may not be as serious as rules or instructions of how to draw state chart diagrams from the requirement document. some practical methods used during our designing the state charts for the elevator system are introduced.1 State chart for DoorControl 22 of 29 . the emergency brake will be triggered.A UML documentation for an elevator system Lu Luo Scenario 7. State chart diagrams are important for constructing executable systems through forward and reverse engineering.The elevator keeps going when hoistway limit is reached 5. not enough direction methods can be followed when drawing the state chart diagram from the requirements. The object has a clear lifetime whose current behavior is affected by its past.2. whose behavior is best characterized by its response to events dispatched from outside its context. In this section.2 State chart Diagram A State chart diagram shows a state machine. It is admitted that there exists a gap in the process of designing a system from requirements to state charts. but they are helpful in practice.5 Emergency Brake 5 – If the car keeps going when the hoist way limit is reached. 5.
2 State chart for DriveControl Emergency Stop EmergencyBrake EmergencyBrake EmergencyBrake DriveSpeed Fast Down Slow Down DesiredFloor / DriveSpeed DesiredDirection = Up DriveSpeed = Stop DriveSpeed = Slow Fast Up AtFloor = DesireFloor Normal Stop AtFloor = Stop AtFloor = Stop Slow Up AtFloor = DesireFloor DoorMotor = Open DoorClosed = False Figure 20: Statechart for DriveControl 23 of 29 .A UML documentation for an elevator system Lu Luo DoorOpen Motor Open DoorReversal AtFloor Motor Stop/Open AtFloor Motor Stop/Open DoorClosed CountDown Motor Close Figure 19: Statechart for DoorControl 5.2.
6 State chart for CarPositionControl DoorClosed = True Off DoorClosed = False On Figure 24: Statechart for CarPositionControl 24 of 29 .2.2.5 State chart for CarButtonControl CarCall Off Arrive at Desired Floor On Figure 23: Statechart for CarButtonControl 5.2.4 State chart for HallButtonControl HallCall Off Arrived at DesiredFloor On Figure 22: Statechart for HallButtonControl 5.3 State chart for LanternControl Lu Luo DoorClosed = False Arrive at Desired Floor Off DoorClosed = True On Figure 21: Statechart for LanternControl 5.A UML documentation for an elevator system 5.2.
provided a good enough requirement document is already there. the state machine for each object will be used. on each one different attention should be paid. as follows: Step 1: Make thorough analysis on the object structure and system architecture. there are several items in the requirement document of our elevator system. or the system as a whole. Instantiation: The initial state can be chosen by the information given here. I am trying to summarize here some practical methods that are used when producing the state charts from the requirement documents. the state chart diagram is chosen to model the behaviors of each object in the system. There is no detailed process in UML telling us how to draw state charts from the requirements documentation or UML diagrams such as class diagrams. a use case. read the requirement carefully. I am not sure whether there is any standard for the format of requirement documents. Take the HallButtonControl as an example. • Replication: this part briefly declares the main function as well as the existence conditions of this specific object.3 Practical methods that fill in the gap between requirements to state charts State chart diagrams can model the behavior of a class. the Instantiation is "All HallCalls are false at • 25 of 29 . but could be used to check when the state charts are finished whether the functions are fulfilled or not. if you want to draw state chart diagrams for each object. This part doesn't help too much when drawing the state charts. From the experience on the course project. In the context of this paper. Step 2: For each class or object in the system. in the periods later on. Most of the information needed for the state charts can be found by this way. In the context of our class project.A UML documentation for an elevator system Lu Luo 5. this part of work is well done by the instructors before we started working on the project by ourselves.7 State chart for Dispatcher DoorClosed = True DoorsOpen DoorClosed = False DoorsClosed AtFloor=none InitState Figure 25: Statechart for Dispatcher 5.2. Taking the one used in our class for example. such as the implementation period and testing period.
Step 8: Draw out the state charts for each object. post-conditions.e. but it's not complete. so the state in our future state chart will probably have two states: On and Off. State: This state has nothing to do with the state chart. i. item by item. The information here helps build what the states will be in the state chart. The state machine stays there waiting for a new hall call to come.d is Stop.A UML documentation for an elevator system Lu Luo initialization" and "All HallLights are off at initialization". execute the state machine by hand. at the same time does not break the constraints. Make sure that nothing is missing or redundant. For the HallButtonControl. actions. Step 5: Check whether all the states are reachable under the combination of events. the Hall Light can be turned on and off. "If DesiredFloor. From these statements we can at least conclude that the init ial state will at least be either in "Hall Call is False" or "Hall Light is off". command both HallLight to Off" makes it change from On state back to Off. Constraints and Behaviors: Both of them will be used to check whether the state machine of this object fulfills the functional requirements of the system. guard conditions. From the information given in the Instantiation part. The original state machine can be now generated. d] is True. In the HallButtonControl example. The input variables will be the triggers of state changes. Let's wait to see whether something else needs to be added. let's continue. • • • Step 3: Now we have some ideas from the requirement items. modifies variables correctly. transitions in the state charts. We can think how many states could the HallLight be in. What is important. entry/exit codes and transitions correctly. The behavior definition says "When HallCall[f. similarly. Step 6: Check whether there is dead state that no (combination of) events can rescue the state machine from being stuck in that state. entry codes and exit codes for the state machine we've got according to the Constraints and Behaviors from the requirement document. Step 7: According to the behaviors. the change of the values of DesiredFloor and HallCall build the set of events triggering all the state changes in our future state chart. the HallLight is the single output this object deals with. In our example. Output Interface: States what will the object being studied do to the outside world. the initial state should be "Hall Light is Off". Step 4: Decide and add the pre-conditions. record the corresponding requirement for tracing. • Input Interface: The input messages that this object will get from other objects. takes actions. which makes up the first state change from On to Off. 26 of 29 .d] to On". label the states. command HallLight[f. we have two states: "Hall Light is On" and "Hall Light is Off". we know how the state machine change are fired from the behaviors description. Intuitively. in this item some notation of variables used for shorthand in the description of behaviors. make sure all the requirement conditions are traversed and the state machine changes states.
Sequence Diagram. Modeling of the network. which are demanding a more pragmatic and comprehensive approach to system development. No single diagram could capture everything about a system's design view. and State Chart Diagram. we use three different views to model the structure of the system: the object construction and the software structure view focus on the software architecture of the system. For example. It is not clear whether in a normal analysis and design process. if used properly with attention paid to the real-time features of a system and combination of different notes. UML supplies sequence diagrams and collaboration diagrams. The UML diagrams used in this documentation are Use Case Diagram. The question here is: does UML notation good enough to design the system architecture provided that we don't have this architecture diagram? The functions of the elevator system described in this paper are still limited to the class project. helps a lot the design and analysis of real-time system and can to some extend address above real-time system aspects. in which no standard UML notation is used. When creating the UML diagrams for the system.A UML documentation for an elevator system Lu Luo 6 Conclusion In this report. which may help filling the gap between requirement and design. Given the popularity and notational robustness of the current version of UML. OO technology can be reasonably exploited in real time developments. with little additional features that are more likely needed in the real world. the systemarchitecture-viewed class diagram is based on the Elevator Architecture by Phil Koopman (attached to this report). Every diagram in UML is just a graphical presentation of some of the aspects of a system. Time constraints. there already exist some components such as the system structure and the state charts. while the system architecture view gives out an sketch of the system hardware and the communication method among system components. which are able to specify the real-time feature of the system by way of marking time constraints aside by the names of message and object. To describe the time constraints. Throughout the process of working on the class project. Definition of task and task communication. UML. To describe the hardware elements and model the network. The UML diagrams have to be combined to express a complete description of a real-time system. which is not quite acceptable to real y time systems. Current object-oriented analysis and design methods focus solel on the software of a system. rather than just software. however. the successful results of our project can be a good answer for the question. The three different views of class diagrams of the system can help to understand better the structural aspect of the system. such as a fire alarm 27 of 29 . the methods concluded above will be still valid or not. how can UML be used in real time systems are paid great attention to. There are some aspects of real-time systems that need to be addressed: • • • • Definition of hardware elements and their characteristics. Some pragmatic methods are given in this paper based on my project experience. a detailed UML documentation for a simulated elevator control system is given. Class Diagram.
given the skeleton of the system. and Patterns. A white paper from Artisan Software Tools. Software Engineering with Objects and Components. [6] Desmond F. Design Principles for Distributed Embedded Applications. UML Distilled. However. A Brief Guide to the Standard Object Modeling Language. Objects. 28 of 29 . these additional functional modules can be added to both the static and the dynamic descriptions of the system. 7 Reference [1] Hermann Kopetz. The Unified Modeling Language User Guide. [5] Bruce Powel Douglass. Objects. Using UML. without too much effort. D'Souza and Ala n Cameron Wills. Developing Real-Time Systems using Object Technology. [7] Alan Moore and Niall Cooling. [3] Perdita Stevens and Rob Pooley. James Rumbaugh and Ivar Jacobson. Frameworks. [4] Martin Fowler and Kendall Scott. and Frameworks with UML. Doing Hard Time: Developing Real-time Ssystems with UML.A UML documentation for an elevator system Lu Luo button or a fan lock. Real-Time Systems. [2] Grady Booch. Components.
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Police oppose plea for CBI probe into cop`s death
New Delhi: The city police on Wednesday opposed in the Delhi High Court a plea seeking a CBI probe into death of Constable Subhash Tomar owing to alleged injuries received by him during the anti-rape stir here, saying the third party "intervention" should not be allowed in a criminal case.
"The petitioner is a lawyer. He is neither an accused nor a witness nor the complainant in the instant case," Additional Solicitor General (ASG) Siddharth Luthra, appearing for Delhi police, submitted before Justice G P Mittal.
Citing a Supreme Court judgement, the ASG said "it has been held that a third party intervention cannot be allowed in a criminal case. Moreover, the petition is not a PIL and the entire case is based on media reports."
He also said the details of ongoing investigation "cannot be shared" with a third party and their disclosure would "prejudice" the investigation. "However, we can share the case diary and other details in a sealed cover if the court asks."
The court was hearing the plea of advocate Gaurav Kumar Bansal seeking a CBI probe into the case alleging contradictions in the statements of various officials, including Delhi Police Commissioner Neeraj Kumar, eye witnesses and the medical expert on the reasons of Tomar`s death.
Earlier, the court had issued notices to police, Delhi government and the Ministry of Home Affairs on the plea that had also alleged that Tomar`s death was portrayed as murder to ensure that the protest against the December 16 gangrape of a 23-year old girl in a moving bus dies down.
During the hearing today, Bansal also cited some judgements and said a probe by CBI was needed as the action of police, which is probing the case, was "suspect".
There are eye witnesses and the doctor who said Tomar died a natural death and he had no injury marks, he said.
The court has posted the matter for hearing on March 12.
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Hotel description Baja Romantica
Boasting an idyllic setting in the tourist resort of Bosa Marina, within walking distance from the beach and just 1 km from the historical centre of Bosa, this elegant hotel offers a perfect combination of classic charm and modern comforts in a beautiful environment. The building presents a Mediterranean style and features spacious, air-conditioned guest rooms, equipped with a bright, charming décor and excellent facilities to make guests' stay as enjoyable a possible. Depending on their needs, guests may choose between different types of accommodation units, ranging from classic and family rooms to more luxurious suites. The property serves a delicious continental breakfast every morning and guests can choose between different dining options in the surrounding area. Travellers may also avail for private on-site parking and benefit of Internet access in public areas.
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Disability-friendly bathroom
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This bright hotel is located in a residential neighbourhood in the heart of Alghero, a town situated in northwestern Sardinia. Guests will find themselves close to the port of Alghero, located some 100 metres away, and within walking distance from the nearest beaches. The airport is to be found 10 kilometres away. This charming property is the ideal accommodation for those wishing to experience all this city has to offer and enjoy the ultimate experience in comfort. The hotel is the perfect choice for tourists visiting Alghero for the first time, or for those who travel for business and have the opportunity to enjoy the charm, natural beauty and traditions of Sardinia despite having little time. The accommodation units range from single to triple and have been tastefully decorated in soothing tones. The onsite services and facilities include complimentary Wi-Fi internet connection and parking.Customer reviews3.4/5of 1 Opinions
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Joe Mauer hit a three-run homer and drove in six runs as the Twins pounded the Blue Jays 14-5 in Fort Myers. Justin Morneau and Brian Dozier both added two-run homers for Minnesota . P.J. Walters gave up three runs over three-plus innings. The Twins host the Cardinals today. Listen for coverage beginning at 12:30pm on 860 AM KNUJ.
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Here's a classic celery science experiment that uses celery and food coloring to demonstrate how plants absorb water.
Your child will be hooked on chemistry after she builds a model volcano by combining an acid and an alkaline substance.
Is it solid or liquid? Create oobleck and witness the amazingly weird oscillation between the two!
A homemade lava lamp gives any room a retro flair. Find out how to make a homemade lava lamp, and learn some science too, with this educational activity.
Help your child measure breezy weather in her environment by making a wind vane for kids, a simple version of the classic scientific measurement tool.
Think you can blow up a balloon without using your mouth? This isn't just a cool trick, it's also a great way to introduce chemistry and biology concepts.
Here's a science experiment that gives your kids a chance to see how fire needs oxygen to burn, with a little math and writing practice thrown in.
Here's a first grade ladybug game that explores how air can move solid objects, and adds some measurement practice, too. Play, learn, and enjoy!
An hour glass, also known as a sand clock, keeps time. In this activity, your child will make her own sand clock and measure the time it keeps.
Did you ever think you could make colors disappear right before your eyes? This science experiment is just like a magic trick: now you see it, now you don't!
Your kid will be captivated as she watches liquids change color before her very eyes during this fun science project that introduces some chemistry basics.
This taste buds science experiment demonstrates how strongly our sense of smell controls what we taste.
Chemistry isn't just incredible ... sometimes its edible! These crystal lollipops are a delicious introduction to chemistry concepts.
Chemistry is a blast with this backyard bomb made from a sandwich bag. All you need are ingredients from the pantry to create a satisfying, and safe, explosion.
This 4th of July, explore fourth grade science and make some safe fireworks in your own backyard using soda pop!
Show your child how and why the microwave works, while demonstrating just how strangely foods can behave while inside the crazy cooker.
Try this chemistry experiment with your curious kid and get some "shocking" results!
How do we know that air exists when we can't see it, taste it, or touch it? Here's a classic experiment that will teach your kid some basics of aerodynamics!
Create a habitat for a butterfly right in your own backyard, and build your first grader's science knowledge while you're at it.
Show your child that the simplest ingredients (salt and water) can be used to illustrate the concept of density!


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Hotels near Nova Southeastern University
Search hotels near Nova Southeastern University in Fort Lauderdale
Trending now in Fort Lauderdale
Hotels within 2 miles of Nova Southeastern University
88 people looked at this hotel in the last hour
Most recent review
"We were pleased with the size of the rooms and the staff is very friendly and helpful. we did have a minor issue and it was taken care of to our satisfaction. if you come in late parking could be an issue but their staff allowed us to park along the side of the entrance and assure us we would n..."
A Traveller, Jul 2016, US
63 people looked at this hotel in the last hour
Most recent review
"Good convince close to a lot restaurants and shops"
A Traveller, Jul 2016, US
49 people looked at this hotel in the last hour
Most recent review
"It's a brand new place. Everything is still new. Only thing I did not like about this place is that you hear everything. Just people having casual conversation, etc. Luckily for me everyone was quiet and well-mannered so it didn't become an issue. But being woken by the next room's alarm clo..."
A Traveller, May 2016, US
Hotels within 3 miles of Nova Southeastern University
325 people looked at this hotel in the last hour
Most recent review
"Improv comedy show brilliant! Lots of options for a night out. Clean and very comfortable."
A Traveller, Jul 2016, GB
101 people looked at this hotel in the last hour
Most recent review
"Nice updated rooms, very stylish lobby, bar & cafe areas. Exceptional value for $, would highly recommend considering I found it on hotels.com for a price that was close to many lesser quality hotels. Very happy with our stay had a late check in and they were very gracious to give us a late che..."
A Traveller, Jun 2016, US
88 people looked at this hotel in the last hour
Most recent review
"Room was for my daughter's 17th Birthdays with friends for a girls sleepover. She love love loved the room."
B, Jul 2016, US
84 people looked at this hotel in the last hour
Most recent review
"Three days two nights for a swim meet. Drove up from Miami. Got early check-in no problem....Staff very friendly. Breakfast more than good enough. Nice spacious room with outstanding Wi-Fi for work... Heard another customer complaining that she would not stay there again because the hallways wer..."
A Traveller, Jun 2016, US
84 people looked at this hotel in the last hour
Most recent review
"Everything was perfect the room was perfectly clean the breakfast was real good the pool was good "
A Traveller, Jul 2016, US
81 people looked at this hotel in the last hour
Most recent review
"The hotel needs to put a sign out front with the hotel name so that went guests arrive especially at night they can see the sign out front from the road and not drive pass the hotel. I understand the sign is out front on the building, but the pam trees are covering the sign, therefore it cannot b..."
A Traveller, Apr 2016, US
71 people looked at this hotel in the last hour
Most recent review
"Rooms need a safe. Other wise all is good. Great location and friendly staff.😀"
D, Jul 2016, US
Map of hotels near Nova Southeastern University
- Sawgrass Mills Mall
- Las Olas Beach
- Seminole Hard Rock Casino Hollywood
- Las Olas Riverfront
- Fort Lauderdale Beach Park
- Greater Fort Lauderdale-Broward County Convention Center
- BB&T Center
- Gulfstream Park Racing and Casino
- Hollywood North Beach Park
- Deerfield Beach Pier
- Westfield Broward Mall
- Diplomat Country Club Golf Course
- Broward Center for the Performing Arts
- Seminole Casino Coconut Creek
- Hollywood Beach Golf Resort
- Broward County Library
- Museum of Art Fort Lauderdale
- The Gallery at Beach Place
- Isle Casino and Racing
- Galleria
Hotels in Fort Lauderdale near Nova Southeastern University
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When you search for hotels near Nova Southeastern University with Hotels.com, you need to first check our online map and see the distance you will be from Nova Southeastern University, Florida.
Our maps are based on hotel search and display areas and neighborhoods of each hotel so you can see how close you are from Nova Southeastern University and refine your search within Fort Lauderdale or Florida based on closest public transportation, restaurants and entertainment so you can easily get around the city. All the hotels details page show an option for free or paid onsite parking.
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Make the most out of your family vacation when you book your accommodation with Hotels.com – book your hotel near Nova Southeastern University, Fort Lauderdale after reviewing the facilities and amenities listed for each hotel.
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