Booch [Booc91] feels that: "Because object-oriented design is a relatively young practice, a discipline for effectively applying the elements of the object model has not yet emerged."
This report will take a look at some of the better established object oriented methods currently available, giving an overview of their operation and comparing the notation that they use. It will also mention some of the tools that are available to support the object oriented methods under consideration.
1) Abstraction, including rules, guidelines, heuristics for the separation of the problem domain into different abstractions; methods for identifying state, services and interfaces for encapsulating objects; and strategy for abstracting commonality for abstract superclasses.
2) Notation and representational verisimilitude, including notation for representing aggregation, inheritance and functional hierarchies, message sending/calling/parameter passing between objects in a seniority hierarchy; representation of autonomous objects and asynchronous message passing; and support for constraint representation and enforcement.
3) Validation, including transformation rules between alternative representations of the design; validation between message sends and interface protocols; overcoming implementation language shortcomings; and support for test generation and metrics for test coverage.
4) Reuse, including heuristics for identifying pre-existing classes from which to develop new application classes; support for different categories of object class and their reusability characteristics; and language independence for logical or architectural design phase.
This report will consider six main object oriented methods, first giving a general overview of the method itself, considering such particulars as: what levels of abstraction the method covers; how the method is applied; what are the goals of each stage; what deliverables and diagrams will be produced by the method; what verification and validation techniques can be employed; and how the method attempts to support reuse. The next sub-section will look at the notation used in the method. This will be done by use of a simple design to describe how a company functions. An overview of the symbols used is given, followed by the design in the notation for the method being considered. Finally, each method will be analysed to attempt to show some of the good, and not so good, features of the method. A list of tools currently available to support each method will also be given. An appendix is provided which highlights the differences in the use of each method by showing a home heating system in the various notations associated with the methods.
In his earlier text Software Engineering with Ada [Booc87], Booch suggests the following steps for analysing a system in preparation for designing a solution in an object-oriented manner:
These steps are based on the earlier work of Abbott [Abbo83]. The problem is defined in a concise, informal textual description, then information on the objects and operations represented in the system can be obtained from this description. Objects are represented by nouns, and operations by verbs. Pressman [Pres87] notes that the first two steps are actually performed during the software requirements analysis stage of development, rather than the design. Booch [Booc86], however, had already noted that object- oriented development, as he described it, is not a complete lifecycle method, but rather, it concentrates on the design and implementation stages.
In his later work [Booc91], Booch suggests the following order of events for the formalisation of the strategy:
Identifying the classes and objects involves finding key abstractions in the problem space and important mechanisms that offer the dynamic behaviour over several such objects. These key abstractions are found by studying the terminology of the problem domain.
Identifying the semantics involves establishing the meanings of the classes and objects identified in the previous stage. The developer should view the objects from the outside, define the object protocol and investigate how each object may be used by other objects.
Identifying relationships extends the previous work to include the relationships between classes and objects and to identify how these interact with each other. Associations such as inheritance, instantiation and uses between the classes are defined, as are the static and dynamic semantics of the mechanisms between the objects. The visibility between classes and objects is also decided upon.
Implementing classes and objects involves delving into the classes and objects and determining how to implement them in the chosen programming language. This is also the step where components are used, and the classes and objects are structured into modules.
In the design method, Booch emphasises the distinction between a 'logical view' of a system, in terms of classes and objects, and a 'physical view' of a system in terms of modules and processes. He also makes a distinction between static and dynamic models of the system. The method he proposes is, however, geared more towards static system descriptions, with less support for dynamic descriptions.
One of the major strength's of Booch's method is the rich notation available. There are diagrammatic notations for producing:
Figure 1.2.1 - A Key to the Booch Class Diagram notation
Figure 1.2.2 - A Booch Class Diagram for a Company
Walker [Walk92] has this to say about Booch's object-oriented approach: "One possible problem is undoubtedly the lack of significant partitioning and layering of diagrams in the Booch method. Booch employs a variety of diagrams for different purposes (e.g. class diagrams, state transition diagrams, object relationship/visibility and message synchronisation diagrams etc.), but within some diagrams, he appears to attempt to cover too much of the system (at least, this appears to be the case in the examples and cases he uses)." He then goes on to say: "Perhaps the criticism of Booch's strategy can be encapsulated in the phrase breadth rather than depth. Booch's diagram notation has sacrificed detail or depth for breadth; this can be useful at the early stages of the design process, but needs to be capable of being reworked to increase the level of detail. In part, this is performed by the textual templates, but they are not structured so as to relate detail in a helpful way to the diagrams; indeed, in some respects, they also lack essential information for the resolution of fine structure within the application."
In terms of designing with reuse, Booch is a little more vague. He states that "Actively looking for reusable software components that are relevant to a new system is a very important activity in any development." He goes on to say that "If we can find a component that is relevant to our to our problem, that component becomes a primitive abstraction with which we can compose the system; thus we are left with a smaller problem to solve." However, the details are hidden in the examples given, and no overall recommendations are given. Booch also advocates the use of application generators where applicable.
The main process in HOOD is called the Basic Design Step. Robinson [Robi92a] describes it admirably: "A Basic Design Step has as its goal the identification of child objects of a given parent object, and of their individual relationships to other existing objects, or the refinement of a terminal object to the level of the code. This process is based on the identification of objects by means of object-oriented design techniques."
In another text [Robi92b], he goes on to further define the Basic Design Step: "A basic design step process is further split into four phases, thus defining a micro life-cycle for a design step." The phases can be summarised as follows:
The context of the object to be designed is stated, with the goal of organising and structuring the data from the requirement analysis phase. This is an opportunity to provide a completeness check on requirements and traceability to design.
1.1 Statement of the problem - the designer states the problem in correct sentences which provides:
1.2 Analysis and structuring of requirement data - the designer gathers and analyses all the information relevant to the problem, including the environment of the system to be designed.
2. Development of solution strategy.
The outline solution of the problem stated above is described in terms of objects at a high level of abstraction.
3. Formalisation of the strategy.
The objects and their associated operations are defined. A HOOD diagram of the proposed design solution is produced, allowing easy visualisation of the concepts and further formalisation. There are five subphases in the formalisation of the strategy:
3.1 Object identification.
3.2 Operation identification.
3.3 Grouping objects and operations (object operation table).
3.4 Graphical description.
3.5 Justification of design decisions.
4. Formalisation of the solution.
The solution is formalised through:
Figure 1.3.1 - A Key to the HOOD Diagram notation
Figure 1.3.2 - A HOOD Diagram for a Company
One of the major criticisms of HOOD is its lack of support for some of the more object-oriented techniques available. Support for inheritance is very poor, as evidenced by the lack of any notation to graphically represent it. The method is perhaps more object based than truly object- oriented.
The only suggestion Robinson gives of designing with reuse is a very vague reference when describing how to produce class objects. "A class object has to be designed separately from the main design as a root object, and either:
The object model, which describes the static structure of the objects in a system and their relationships. The main concepts are:
1) Analysis - the building of a model of the real world situation, based on a statement of the problem or user requirements. The deliverables of the analysis stage are:
2) System design - the partitioning of the target system into subsystems, based on a combination of knowledge of the problem domain and the proposed architecture of the target system (solution domain). The deliverables of the system design stage are:
3) Object design - construction of a design, based on the analysis model enriched with implementation detail, including the computer domain infrastructure classes. The deliverables of the object design stage are:
4) Implementation - translation of the design into a particular language or hardware instantiation, with particular emphasis on traceability and retaining flexibility and extensibility.
Figure 1.4.1 - A Key to the OMT notation
Figure 1.4.2 - An Object Model of a Company
The concept of using three views to represent a system presented in the OMT is potentially very powerful, but can also be considered to be very complex. It is unclear whether the views are to be developed independently of each other, or whether knowledge of one model should be used to influence construction of another. It would seem logical to ensure that the concepts in the different views are properly defined and interrelated, or much confusion could occur at the design stage of the development where the models are to be integrated.
Walker [Walk92] notes two main areas in which the OMT method is lacking. First, "there is no serious attempt to address the systematic reuse of software or design components. Secondly, the management of the software development process, including the establishment of suitable metrics for the measurement of progress and quality, is almost totally neglected." He feels, however, that, in terms of a technical approach to object-oriented software development, "Rumbaugh et al. have clearly established the current state of the art."
It is interesting to note that Rumbaugh is now advocating the inclusion of Jacobson's use cases (see section 1.8.1) as a 'front-end' to the OMT method [Rumb94]. He says, "We feel that use cases fit naturally on the front end of the published OMT process and supplement the existing user-centered features of the method." He goes on to qualify his recommendation of use cases, feeling that "a combination of direct domain analysis and use cases is an effective approach to starting analysis, rather than depending on use cases alone."
According to a recent survey conducted by the Object Management Group, OMT is currently the most popular of the standardised object oriented development methods (in house methods were the most used, with OMT a close second). One of the reasons for its success may be the variety of tool support available for the method, some of which are included in the table below.
In addition, Rumbaugh et al. discount the utility of defining classes in isolation for general reuse. "Planning for future reuse takes more foresight and represents an investment. It is unlikely that a class in isolation will be used for multiple projects. Programmers are more likely to reuse carefully thought out subsystems, such as abstract data types, graphics packages, and numerical analysis libraries." Their suggestions on 'style rules for reusability' concentrate on methods, and, on the whole, reiterate the standard practices of structured programming, emphasising such styles as encapsulation with minimal coupling and high cohesion.
In RDD, for each class, different responsibilities are defined which specify the roles of the objects, and their actions. In order to fulfil these responsibilities, classes need to collaborate with each other. Collaborations are defined to show how the objects will interact. The responsibilities are further grouped into contracts which define a set of requests that objects of the class can support. These contracts are further refined into protocols, which show the specific signature of each operation.
Subsystems are introduced to group a number of classes and subsystems of a lower level in order to abstract a certain functionality. Subsystems also have contracts which must be supported by some class in the subsystem. The RDD method consists of two main phases. An overview of these phases is given below:
1) The exploratory phase, which consists of:
- find responsibilities
- assign responsibilities to classes
- find additional responsibilities by looking at the relationships between classes
- find and list collaborations by examining responsibilities associated with classes
- identify additional collaborations by looking at relationships between classes
- discard and classes that take part in no collaboration (as client or server)
2) The analysis phase, which consists of:
- draw a complete collaborations graph for the system
- identify possible subsystems
- simplify the collaborations between and within subsystems
- define protocols for each class, by refining responsibilities into sets of method signatures
- write a specification for each class
- write a specification for each subsystem
- write a specification for each contract
Figure 1.5.1 - A Key to the CRC notation
Figure 1.5.2 - A Collaboration Graph for a Company
This type of simplicity can be considered both a strength and a weakness. It makes the design method much more intellectually and notationally manageable; however, there is a strong dependency on the requirements specification document (or other sources of information) being sufficiently clear, precise and understandable to express a design using the recommended concepts.
RDD only considers the design activity, there is no consideration of domain or problem analysis, or requirements capture. The class concept is central - all other concepts are there to describe classes and their interdependencies. The design activity produces what is really a single model in a single notation. There are no other models, such as models of dynamic behaviour. The notation is also not expressive enough to adequately show the design captured by the process.
The heuristics of this design method are explicit and generally well explained. Gossain [Goss91] feels that Wirfs-Brock et al. provide an extremely useful introduction to the core concepts of object-oriented design, but feels that they miss out on a vision of the 'big picture'. He also feels that their design approach would not scale up well to large systems.
Also, in the identification of candidate classes, Wirfs-Brock et al. direct the designer to "identify candidates for abstract superclasses" which can be made reusable by following their design guidelines.
1) Finding Class & Object - specifies how classes and objects should be found. The first approach is given by starting with the application domain and identifying the classes and objects forming the basis of the entire application and, in the light of this, the systems responsibilities in this domain are analysed.
2) Identifying Structures - this is done in two different ways. First, the generalisation-specialisation structure, which captures the hierarchy among the identified classes. Second, the Whole-Part structure, which is used to model how an object is part of another object, and how objects are composed into larger categories.
3) Defining Subjects - this is done by partitioning the Class & Object model into larger units. Subjects are groups of Class & Object. The structures identified earlier can be used.
4) Defining Attributes - this is done by identifying information and associations for every instance. This involves identifying the attributes needed to characterise each object. The identified attributes are placed at the correct level in the inheritance hierarchy.
5) Defining Services - defining the operations of the classes. This is done by identifying the object states and defining services for accessing and altering that state.
The final result of the analysis stage is a model of the problem domain in terms of five layers:
An object-oriented design model consists of the following components:
Figure 1.6.1 - A Key to the Coad/Yourdon OOA Model notation
Figure 1.6.2 - A Coad/Yourdon OOA Model of a Company
The four components of the design approach are not presented with enough detail to be put directly into practice. However, their approach to OOA and design is easy to understand, and their method is put across at a level which avoids some of the difficult complexities of formalised object orientation. As such, it gives a good introduction to object orientation. However, there are sufficient flaws in the method to avoid it for large or highly complex systems.
1) Partition the system into domains - The application domain is defined as the subject matter that is of concern to the enduser of the system. The service domains may include the user interface and other external interfaces of the system. The architectural domain covers the hardware and software which will be used to build and run the desired system. The implementation domains will include the operating system(s) and programming language(s) that will be used to build the system. A Domain Chart is used to depict these domains, and the interrelationships between them (which are referred to as bridges).
2) Analyse the application domain - The application domain is analysed using Shlaer/Mellor's integrated set of Object-Oriented Analysis (OOA) models. This produces a set of formal models which are depicted in three related diagrams:
4) Extract the requirements for the service domain - Each service domain is considered in terms of the requirements that each of the other domains make of it. This allows for the purpose of each domain to be identified for the next step.
5) Analyse the service domains - The service domains are analysed using the OOA models, by the same process used in step 2. Due to the client/server nature of the relationships between the domains, server domains must not be analysed until sufficient analysis has been done on their clients to ensure that all the requirements of the server have been identified.
6) Specify the components of the architectural domain - The architectural domain is specified using OOA, but can be designed using whichever design method is deemed appropriate. If an object oriented design is required, Shlaer/Mellor's Object Oriented Design LanguagE (OODLE) is recommended. OODLE uses four types of diagram interrelated by a layering scheme to depict the design of an object oriented program, library or environment:
structures, which represent a prescription for translating the OOA models of the client domains. Structures are built as a combination of code and data that needs to be completed by adding elements from the client domains. When built, structur es are called templates, and are 'populated', or completed using the domain specific information, prior to compilation.
8) Translate the OOA models of each domain using the architectural components - The details of the final step depend a great deal on the design chosen for the system, and the architectural components created. However, the general principles for multitasking and multiprocessor systems can be described in two activities:
Figure 1.7.1 - A Key to the OODLE Diagram notation
Figure 1.7.2 - A simplified OODLE Diagram for a Company
The OOA model simulation is well defined within the method, and provides a means for testing the validity of the system which has been captured in the models. Due to the structured nature of the simulation, much of the process can be automated successfully. The process of populating the structures in the architectural domain can also be partially automated, making the templates built as a result of this method highly reusable.
One of the key concepts in OOSE, as described by Jacobson [Jaco92] is that of the use case. A use case is defined as "a behaviorally related sequence of transactions" which a user will perform in a dialogue with the system. Thus, each use case is a specific way of using the system, and when a user inputs a stimulus, an instance of a use case executes and starts a transaction belonging to that use case. Based on this view of the system, Jacobson associates the use case model with five other models of the system:
OOSD is described as being methodology independent. Graham [Grah93] says that it is "strictly speaking, not a method, but a notation to which methodological rules can be added. " As Wasserman et al. [Wass90] put it: "it is not our intent to prescribe a single best method for design...the OOSD notation is neutral...it is expected that designers will develop and use their own design esthetics and design metrics within the framework of OOSD, which simply carries a valid design notation...OOSD supports a wide range of design philosophies."
The main entities in OOSD are:
One of the central notions in JSD is that of the Long Running Process (Program) (LRP). An LRP is made up of the time-ordered sequence of actions that an entity performs or suffers. Walker [Walk92] notes that this "view of the 'Long Running Process' with its state information is somewhat analogous to the notion of 'behaviour' (the implementation of an object's responsibilities) in Wirfs-Brock's Responsibility-Driven Approach". The Responsibility-Driven Approach, however, "involves a much more detailed analysis of the nature of the operations performed or suffered by an object with respect to its environment/interacting objects. Suffice to say, the notion of entities/objects being characterised by the set of operations or functions that they perform over their lifetime is clearly very powerful, and is employed in a number of existing design methodologies."
JSD has no concept of inheritance in its method. It is, therefore, more of an object-based method than truly object-oriented. However, there is a remarkable resemblance between the JSD suggestions for identifying entities and actions, as explained by Jackson [Jack83]: "make a comprehensive list of nouns and verbs we encounter in our study of reality: each noun is a possible entity; each verb is a possible action"; and the method for object and operation identification proposed by Booch [Booc91].
Ince [Ince91] says that "Polymorphism allows a developer to build up a library of reusable objects, and contributes greatly towards the ability to develop reusable software." Wiener and Pinson [Wien88] consider one of the main goals of object-oriented software development to be "to shorten the time and lower the cost of development by using reusable software components in the form of baseline classes and by employing incremental problem solving using subclasses." Tsichritzis and Nierstrasz [Tsic89] seem to consider that because of object-oriented programming's heavy emphasis on reuse, that "we can expect extremely large collections of reusable objects to be available to us." They feel that the problems of the future will be associated with managing such large collections of objects, and suggest that perhaps expert systems will be the appropriate tools for helping programmers to find their way through databases of reusable object classes.
It has been seen, however, that among the object-oriented design methods available, there is a lack of explicit provision for reuse [Goss90]. Udell [Udel94] also expresses this opinion: "The traditional OOP vision was, at best, vague on the subject of reuse: Objects would appear as by- products of software development, a market would emerge, and programmers would become producers and consumers of objects." This unstructured, and rather naive, view of reuse can be seen in several object-oriented texts.
Meyer [Meye88] offers considerably more advice on the construction of reusable classes in his text. He suggests that: "A good object-oriented environment will offer a number of predefined classes implementing important abstractions. Designers will naturally look into these to see if there is anything they can use...New applications, if properly done, will also produce more specialized reusable classes. As object-oriented techniques spread, the number and abstraction level of available components grow."
Tello [Tell91] also questions the provision for reuse in object-oriented methods. He states: "some say that the key advantage of OOP is the ability to reuse code for many different programs, but, by itself, this is not significantly different from library functions." Mullin [Mull89] would agree: "As most books available today on OOP say, one of the major benefits of objects is that they are reusable. So are C functions. The difference is that objects, representing both data structures and operations that can be performed on these structures, represent functional packages, requiring no additional work on the part of the programmer to use them."
Raj and Levy [Raj89] note that one of the problems with inheritance in object-oriented systems is that "classes are not automatically reusable". They suggest that for successful reuse, inheritance requires the use of a set of coding rules and a set of design rules. Johnson and Foote [John88] would agree with this second point, as they present a set of 13 rules for designing reusable classes. Udell [Udel94] suggests that "object technology failed to deliver on the promise of reuse", but that componentware; in which components are encapsulated, or combined into a single, separate unit with a well defined interface, in order to make them reusable; is the way forward for reusability.
Winblad et al. [Winb90] note that "Software reuse does not occur by accident, however - even with object- oriented programming languages. System designers must keep the advantages of reusability in mind, planning ahead to reuse what already exists and designing reusability into the new components they create. This requires that programmers adopt new programming behavior, values, and ethics. Borrowing classes created by others must be considered more desirable than implementing a new class. Reviewing existing code to identify opportunities for reuse must have priority over writing new code. Finally, programmers must create simple, reusable classes rather than complex, inscrutable classes. Simplicity is a major tenet of the general philosophy of object orientation."
It is important to note that no one method, technology or technique will solve all the problems associated with reuse. There will always be complications, and these must be expected and planned for. Burd and McDermid [Burd92] note that: "Risks are involved in all software developments, however, often those projects which employ reuse are susceptible to greater risks than those which do not." However, by the use of object-oriented techniques, with their excellent support reuse, these risks, and the difficulties involved in successful reuse can be reduced. This view is confirmed by Burd [Burd93]: "Object oriented design displays the most promise as a re- use methodology...Object orientation on its own isn't sufficient to solve all the problems associated with re-use. This can be achieved only by providing well-defined support that enables re-use to be integrated into a suitable lifecycle model."
It is with this in mind that a CASE tool is proposed which will provide not only support for the use of an object oriented method in software development, but will allow existing code to be reverse engineered to abstract general design decisions, structure the documentation associated with the code in such a way as to make it useful to the developers, and will also provide the techniques and functionality required to support a software reuse program. Although a tool will not solve all the problems that inhibit software developers in a small company from structuring their development in such a way as to gain great benefits for software reuse, it is felt that, with the technology available, it will be easier to put the processes in place that will allow the benefits of software reuse to be maximised.
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Each room has a temperature sensor which measures the current temperature (tc) of the room. Each room is equipped with a water valve that controls the flow of hot water into the radiator of the room. The valve can be either fully open or fully closed. If the current temperature is less than the desired temperature and the living pattern indicates that the room is to be heated at this time, the valve is opened to allow hot water to flow into the room.
The timer provides a continuously incrementing count, one increment for every second of elapsed time.
The furnace consists of a boiler, an oil valve, an ignitor, a blower and a water-temperature sensor. The furnace heats the water in the boiler, and the water can then be circulated to one or more rooms of the home.
The furnace is alternately activated and deactivated by the heat-flow regulator as needed to maintain the required temperature for each room. The furnace indicator shows whether the furnace is currently on or off. If a fault develops in the furnace, the fault indicator is lit. This is associated with the fault reset switch, thus the user can reset the fault indicator by setting the switch to on.
The heat flow regulator interacts with other components of the home heating system to determine the heating needs for each room and to control the flow of heat necessary to satisfy those requirements. The heat flow regulator maintains a working temperature and a living pattern for each room without regard to the running state of the furnace. The heat-flow regulator determines that a given room needs heat whenever the current room temperature is equal to or less than (tw- 2) degrees Farenheit and determines that a room does not need heat whenever the current room temperature is equal to or greater than (tw+2) degrees Farenheit.
This is only if the living pattern shows that the room is currently to be heated. If the furnace is not running, the heat switch and the fault reset switch/indicator are both on, and at least one room needs heat, the heat-flow regulator activates the furnace and then routes heat to the appropriate rooms. If the furnace is running, the heat-flow regulator deactivates the furnace whenever either the heat switch or the fault reset switch/indicator is off and no rooms need heat. The minimum time for furnace restart after prior operation is five minutes.
Name: HeatFlowRegulator Documentation: text Cardinality: 1 Hierarchy: Superclasses: Object Public Interface: Uses: Furnace Home OperatorInterface Room Operations: initialise: furnace: operator: needsHeat: noLongerNeedsHeat: release respondToFaultResetSwitch respondToFurnaceFault respondToFurnaceNotRunning respondToFurnaceRunning respondToHeatSwitchOff respondToHeatSwitchOn Implementation: Fields: roomsNeedingHeat Operations: add: remove: size Name: OperatorInterface Documentation: text Cardinality: 1 Hierarchy: Superclasses: Object Public Interface: Uses: HeatFlowRegulator Operations: heatStatus initialise: release reportFault reportFurnaceStatus: Implementation: Uses: FaultResetSwitchIndicator FurnaceStatusIndicator HeatSwitch Fields: theFaultResetSwitchIndicator theFurnaceStatusIndicator theHeatFlowRegulator theHeatSwitch theView Concurrency: active Name: HeatSwitch Documentation: text Cardinality: Hierarchy: Superclasses: Metaclass: Public Interface: Operations: initialise: switchOn switchOff Implementation: Fields: heatSwitchStatus Name: FaultResetSwitchIndicator Documentation: text Cardinality: Hierarchy: Superclasses: ToggleSwitch Metaclass: Public Interface: Operations: switchOn respondToFault Implementation: Fields: theView Operations: switchOff Name: ToggleSwitch Documentation: text Cardinality: 0 Hierarchy: Superclasses: Object Metaclass: Public Interface: Operations: toggleState returnState Implementation: Fields: state Name: FurnaceStatusIndicator Documentation: text Cardinality: Hierarchy: Superclasses: Indicator Metaclass: Public Interface: Operations: initialise: Implementation: Fields: furnaceStatus Name: Indicator Documentation: text Cardinality: 0 Hierarchy: Superclasses: Object Metaclass: Public Interface: Operations: reportStatus setStatus Implementation: Fields: status theView Name: HeatingSystem Documentation: text Cardinality: Hierarchy: Superclasses: Object Metaclass: Public Interface: Operations: powerDown powerUp Implementation: Fields: theFurnace theHeatFlowRegulator theHome theOperatorInterface Name: Home Documentation: text Cardinality: Hierarchy: Superclasses: Metaclass: Public Interface: Operations: closeAllWaterValves openWaterValve closeWaterValve needsHeat noLongerNeedsHeat Name: Timer Documentation: text Cardinality: Hierarchy: Superclasses: Object Metaclass: Public Interface: Operations: reportElapsedSeconds initialise: release Implementation: Fields: elapsedSeconds theSemaphore timerProcess Name: ClockCalendar Documentation: text Cardinality: Hierarchy: Superclasses: Timer Metaclass: Public Interface: Operations: reportCurrentTime reportCurrentDate initialise: Implementation: Fields: dayOfWeek hour minute second Operations: respondToTick Name: Furnace Documentation: text Cardinality: 1 Hierarchy: Superclasses: Object Public Interface: Uses: HeatFlowRegulator Operations: activate deactivate initialise: release Implementation: Uses: BoilerTemperatureSensor ClockCalendar CombustionFaultSensor Blower OilValve Ignitor OilFaultSensor Fields: currentState itsSemaphore theBoilerTemperatureSensor theCombustionFaultSensor theHeatFlowRegulator theBlower theOilValve theIgnitor theOilFaultSensor theView timeDelay Operations: postFault postNotRunning update: Concurrency: active Name: Room Documentation: text Cardinality: n Hierarchy: Superclasses: Object Public Interface: Uses: HeatFlowRegulator Operations: closeWaterValve initialise: location: heatFlowRegulator: name openWaterValve release Implementation: Uses: ClockCalendar CurrentTemperatureSensor DesiredTemperatureSensor LivingPattern WaterValve Fields: currentState name theCurrentTemperatureSensor theDesiredTemperatureSensor theHeatFlowRegulator theLivingPattern theSemaphore theView theWaterValve Operations: heatingRoom: current: desired: setInitialState startHeating stopHeating update: Concurrency: active Name: DesiredTemperatureSensor Documentation: text Cardinality: Hierarchy: Superclasses: TemperatureSensor Metaclass: Public Interface: Operations: setDesiredTemperature initialise: Implementation: Fields: desiredTemperature theView Name: CurrentTemperatureSensor Documentation: text Cardinality: Hierarchy: Superclasses: TemperatureSensor Metaclass: Public Interface: Operations: initialise: Implementation: Fields: currentTemperature Operations: monitorCurrentTemperature Name: TemperatureSensor Documentation: text Cardinality: 0 Hierarchy: Superclasses: SimpleSensor Metaclass: Public Interface: Operations: reportTemperature Implementation: Fields: temperature Name: SimpleSensor Documentation: text Cardinality: 0 Hierarchy: Superclasses: Object Metaclass: Public Interface: Operations: respondToExternalChange Implementation: Fields: value theSemaphore Operations: monitorExternalValue Name: WaterValve Documentation: text Cardinality: Hierarchy: Superclasses: SimpleValve Metaclass: Public Interface: Operations: initialise: Implementation: Fields: waterValveStatus Name: SimpleValve Documentation: text Cardinality: 0 Hierarchy: Superclasses: Object Metaclass: Public Interface: Operations: openValve closeValve Implementation: Fields: valveStatus
1) Heat Flow Regulator initialise needsHeat noLongerNeedsHeat release respondToFaultResetSwitch respondToFurnaceFault respondToFurnaceNotRunning respondToFurnaceRunning respondToHeatSwitchOff respondToHeatSwitchOn 2) Operator Interface heatStatus initialise release reportFault reportFurnaceStatus: 3) Toggle Switch toggleState returnState HeatSwitch: initialise HeatSwitch: switchOn HeatSwitch: switchOff FaultResetSwitchIndicator: switchOn FaultResetSwitchIndicator: respondToFault 4) Indicator reportStatus setStatus FurnaceStatusIndicator: initialise 5) Room closeWaterValve initialise name openWaterValve release 6) Simple Sensor respondToExternalChange 7) Temperature Sensor reportTemperature CurrentTemperatureSensor: initialise DesiredTemperatureSensor: initialise DesiredTemperatureSensor: setDesiredTemperature 8) Simple Valve openValve closeValve WaterValve: initialise 9) Furnace activate deactivate initialise release 10) Timer initialise reportElapsedSeconds release ClockCalendar: initialise ClockCalendar: reportCurrentTime ClockCalendar: reportCurrentDate