Flashcards
SCC 204 - Control Modelling and OO introduction
Cards in this deck (41)
- 1What are the two models of control?Centralised control
Event-based control - 2What is the centralised control?One sub-system has overall responsibility for control and starts and stops other sub-systems.
- 3What is event based control?Each sub-system can respond to externally generated events from other sub-systems or the system’ s environment.
- 4Within a centralised control, what does a control sub system take responsiblity of?A control sub-system takes responsibility for managing the execution of other sub-systems.
- 5Describe the process of a call-return model and where is it applicable?– Top-down subroutine model where control starts at the top of a
subroutine hierarchy and moves downwards
– Applicable to sequential systems. - 6Describe the process of a manager model and where it's applicable?Applicable to concurrent systems
– One system component controls the stopping, starting and
coordination of other system processes
– Can be implemented in sequential systems as a case statement - 7What are event driven systems driven by?Driven by externally generated events where the timing of the event is out of the control of the sub-systems which process
the event. - 8What are the two principle event driven models?Broadcast models
Interrupt models - 9What are broadcast models?An event is broadcast to all sub-systems. Any subsystem which has been programmed to handle the event may do so;
- 10What are interrupt models?Used in real-time systems where interrupts are detected by an interrupt handler and passed to some other component
for processing. Used in systems that require stringent timing - 11Within broadcast model, what happens when a sub-system registers an interest for specific events?Sub-systems register an interest in specific events. When these occur, control is transferred to the sub-system which can handle the event (publisher-subscriber pattern).
- 12What is broadcast model effective in?Effective in integrating sub-systems on different computers in a network.
- 13Within broadcast model, control is not embedded in the event or message handler, how do sub system integrate/communicate then?- Sub-systems decide on events of interest to them.
– However, sub-systems don’t know if or when an event will be handled. - 14Where are interrupt driven systems used?Used in real-time systems where fast response to an event is essential.
- 15How are interrupts handled in an interrupt driven system? Benefits and drawbacks of interrupt driven systems?There are known interrupt types with a handler defined for each type.
• Each type is associated with a memory location and a hardware switch causes transfer to its handler.
• Allows fast response but complex to program and difficult to validate. - 16What is modular decomposition? Please give examples?structural level where sub-systems are
decomposed into modules.
– Examples include objects, dataflow, components, services etc. - 17In an object model, how is the system decomposed?In an object model the system is decomposed into interacting objects
- 18What is an object?an object represents an entity, be it
physical, conceptual, or software - 19What 3 components does an object have?State
Behaviour
Identity - 20How can a state be represented? What happens to the state overtime?• Represented by a set of attribute values + the links the object may have with other objects
• Changes over time - 21How is behaviour defined in an object?Defined by what it does in response to receiving a request from another object
- 22What is identity in relation to the components of objects?Each object has a unique identity, even if its state is identical to that of another object
- 23A class is a description of a group of objects with common what?Attributes
Behaviour
Links
Semantics - 24A class is an abstraction in that it?– Emphasizes relevant characteristics (i.e. its interface)
– Suppresses other characteristics (i.e. its
implementation) - 25What is an attribute and what does it describe?An attribute is a property of a class
– It describes a range of values that the property may hold in objects (i.e. instances) of that class - 26What is an operation?An operation is a method or function that can be performed by an instance of a class
- 27An object is an instance of a class. To create a particular instance of an object, what must happen to the class?To create a particular class of object, the class must be instantiated
– The terms object and instance are synonymous - 28Some classes have a certain amount in common with each other … which means– Classes can be arranged in a generalisation hierarchy that shows the relationship between general and more specific classes
– The more specific class is completely consistent with its parent class but includes additional properties - 29What does object orientation allow?Object-orientation allows classes to inherit commonly used state and behaviour from other classes
- 30What do subclasses inherit in relation to their superclasses?Subclasses inherit all the attributes and operations of their superclasses, but are also able to define additional attributes
and operations - 31What is multiplicity?Multiplicity identifies the number objects of one class that relate to a single
object of the association class - 32What is aggregation?Aggregation is a special form of association that connotes a “whole/part” relationship
- 33What is composition?– Composition is a form of aggregation involves a strong relationship between an
aggregate object and its component objects (i.e. parts) - 34In a composition, the component existience depends on what?In a composition the component object exists as component only within the
aggregate object - 35What is an interface?An interface is a set of method signatures
- 36How many interfaces may a class implement?A class may implement several interfaces
- 37How many times can an interface be implemented by a class?An interface may be implemented by several classes
- 38What can't an interface have, unlike a traditional class?Unlike a traditional class, an interface can’t have state or method implementations, and it can’t be instantiated
- 39What is polymorphism?The use of several versions of a method, one in each derived class. The ability to redefine methods for derived
classes - 40What does polymorphism enable?– Enables an instance of the base class’ method to be interpreted variously at run-time, depending on what derived
class the object is an instance of - 41—
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- Flashcards on SCC 204 - Control Modelling and OO introduction, created by Ayo Olutobi on 29/04/2017.
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