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96 Cards in this Set
- Front
- Back
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Define design, with regards to software. |
The organization of high-level software architecture and "close to code" systems. |
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Give some examples of design decisions. |
1) Applying design patterns 2) separating access policy from business logic 3) picking specific class and method naming convention |
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What are the different domains of software design? |
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What is structure-oriented design? |
Primarily concerned with the structure of the components of a program/system, their interrelationships, and what principles govern its evolution over time. |
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What is decision-oriented design? |
Primarily concerned with the principal designs made about the system. |
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What is organization-oriented design? |
Designs constrained by the communication structures of the developing organization. |
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What is "kitchen sink" design? |
In which the architecture is a set of significant decisions about...EVERYTHING: - the organization of a software system, - the selection of the structural elements and their interfaces - their behaviour as specified in thecollaborations among those elements, - the composition of these structural andbehavioral elements into progressively larger subsystems, - architectural style |
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What are the two levels of software design? |
Software architecture (high level) Detailed Design (close to code) |
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Define software architecture. |
The high level decomposition of system or software - elements and their connections - allocation of functions to elements |
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True/False: an architecture has 1 specific view. |
False. Multiple views are can be created depending on the target audience/stakeholder. |
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True/False: architecture focuses of the more stable aspects of a system that are less likely/more difficult to change. |
True |
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What is the purpose of an architecture? |
- Provide a decomposition/solution that meets the functional and quality requirements. - Allow for effective concurrent development - Fitness for future - Enable reuse |
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How can you improve concurrent development? |
- Simple interfaces - optimize communication |
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What does fitness for future involve? |
- Decoupling low level decisions from high level. - Localize change - Extension and evolution |
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What are the responsibilities of an architect? |
- Champion architecture - integrate info from different stakeholders - build consensus among stakeholders - identify and introduce best practices - perform mining activities to identify common parts - develop road map - ensure architecture is followed (ie. reviews, checks) |
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What are the qualifications of an architects? |
- Strong abstractions skills - Excellent communication skills - Ability to develop multi-disciplinary perspective - Experience in a broad set of different design implementation, testing - Excellent design skills - Ability to think strategically - knowledge of architectural concepts - Eagerness to learn |
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What are the 7 main steps in the design process? |
1. Know and understand customer's needs 2. Generate solutions (Ideation) 3. Conceptualize alternative solutions 4. Analyze solutions 5. Select solution 6. Validate it 7. Iterate |
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True/false: Requirements engineering provides the problem definition, consisting of functional requirements and quality requirements. A design has to satisfy both. |
True. |
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What is the difference between design constraints and requirements? |
Constraint: quality properties that should be minimized/maximized Requirement: properties that should be satisfied or not |
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True/False: Design constraints are a part of the requirement specification. |
False. They emerge from design decisions, not the problem spec. |
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What are 2 parts of the Synthesis step? |
1. Generation of Ideas 2. Conceptualization |
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__________ and ___________ are checked in the Analysis Step. |
Requirements and Constraints |
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What are 2 techniques used in the Decision Making step? |
1. Checking weights of each design criteria 2. visualize alternatives in a multidimensional space |
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Describe 2 validation techniques. |
1. Design reviews
2. Have the first release evaluated by customer |
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True/False: It is a good practice to think about optimization in the Synthesis step. |
False. |
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What are the 3 groups of design criteria? |
- Fitness for purpose - Fitness for future - Cost |
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Define functional requirements. |
Functional requirements are concerned with what the system should do and how it should behave. |
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Define quality requirements. |
How well the system should support functionalities. |
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Give 2 examples of quality requirements (4). |
- Usability - Performance - reliability - security |
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True/False: quality requirements may specify acceptable ranges. |
True |
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True/False: Quality requirements can be used as design criteria. |
True |
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Modifiability is concerned with fitness for: - Future or - Purpose? |
Future |
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Name 2 qualities to measure modifiability by (4). |
- Readability - Maintainability - portability - extensibility |
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What are the 4 types of maintenance? |
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Define module. |
A unit of system decomposition with a well-defined purpose and interface. |
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What are some (4) benefits of modular design? |
It allows: 1. comprehension of system piece-by-piece 2. parallel development 3. evolution (change implementation by not interface) 4. independent compilation of interface and implementation |
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Define interface. |
Interface: a contract between a module and its environment. |
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What is the difference between the provided interface and the required interface? |
Provided: the services the modules provides and any guarantees. Required: the services the module requires from its environment and assumptions. |
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True/False: interfaces should not change often. |
True |
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What is the difference between syntactic and semantic interfaces? |
Syntactic: specifies exposed services (ie. function signatures) Semantic: specifies what the module does and how it behaves. (ie. side effects, when it fails) - often documentation |
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What is a reasonable number of modules? |
7 +- 2 Rule. |
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What is the Axiom of Independence? |
Modules sand requirements are related such that a specific module can be adjusted to satisfy its requirement without affecting other requirements. |
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What is crosscutting? |
When a requirement is implemented in several different modules across the module hierarchy. |
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What is tangling? |
When several different requirements are implemented in the same module. |
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True/False: tangling is less problematic that crosscutting |
True |
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True/False: Architects should strive to localize quality requirements. |
False. For example, how would you localize performance? |
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What implementation details are usually hidden? (4) |
- Data representation - Properties of device - Implementation of world models - Mechanisms that support policies |
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Requirements that are more likely to change are more important to ________. |
Localize. |
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How would you analyze modifiability? (6) |
- Stimulus: changing functionality/quality - Source: customer, developer, sys admin - Artifact: system, UI, component - Environment: Design/compile/run time - Response: locate places to modify - Metrics: cost and effort |
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How can you improve Modifiability? (2) |
- Increase cohesion
- Reduce coupling |
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Define cohesion. |
A measure of the coherence of a module amongst the pieces of that module. |
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Define Coupling. |
The degree of relatedness between modules. |
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Functions within a modules can be related by ________ and ________. |
Topic, interaction |
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What is Coincidental Cohesion? |
When unrelated code is inserted into a random module. |
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What are god classes/modules? When are they justified? |
Classes/Modules that have assumed too many responsibilities. Libraries are examples of justifiable god classes. |
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Define temporal cohesion. |
Gathers operations that are executed at a similar point in time. Leads to code duplication. |
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Define control-flow cohesion. |
Code that is merged into a single module to share a common control flow. (Like switch statements) |
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What are the different types of coupling? (7) |
- Data: A provides data to B - Control: A controls (the inside of ) B - Service: A calls B's service - Identity: A knows B's identity - Location: A knows B's location - Quality of Service: A expects B's good service - Content: A includes code from B |
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What is the weakest coupling type? |
Data coupling |
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To reduce coupling, minimize the ________ and ________ of dependencies. |
Number, strength |
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True/False: prefer inheriting implementation over interface. |
False. Implementation Inheritance introduces strong coupling. Prefer interface. |
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To avoid control coupling, consider using _________. |
Polymorphism |
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What is Stamp coupling? |
Passing more data to a module than necessary. |
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Define refactoring. |
To improve design without changing functionality. |
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What is the role of testing in design? |
To enable refactoring without fear of breaking code. |
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What are 2 problems with code duplication? |
- Parallel maintenance - More code to maintain |
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How can you fix code duplication? (3) |
- Extract method - Extract class and pull-up method - Form template method |
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When is code duplication justifiable? What are the benefits? |
When you need clones/duplicates of an object for different project. - No coupling - customize to context - Optimization |
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Name 4 code smells. (12) |
- Duplicated code - Long method - Large class - Comments - Switch statement - Primitive Obsession - Long parameter list - feature envy - data clumps - shotgun surgery - direct constructor call - speculative generality |
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How can you fix Long Methods? |
- Break up into smaller private methods (extract) - delegate subtasks to member variables that "know best". (replace data value with object) - for example, look at comments for major steps |
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How can you fix Large Class? |
- Gather up the little pieces into aggregate member variables - Delegate methods to the new member variables |
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What are symptoms of Long Parameter List? How can you fix each? |
- Doing too much - break up into subtasks - Too "far from home" - localize passing parameters - too many disparate member variables - Gather params into aggregate member variables |
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What is shotgun surgery? How can you fix it? |
Each time you want to make a single, seemingly coherent change, you have change lots classes in little ways. - Can mean poor cohesion or high coupling Look to do some gathering |
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What is Feature Envy? How can you fix it? What are some exceptions? |
When a method seems more interested in another class than the one it's defined in. Try moving it. Exceptions: Visitor, iterator, and strategy design |
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What are Data Clumps? How can you fix it? |
When a set of variables seem to "hang out" together. Combine to aggregate member variable. May cause some feature envy. |
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What is Primitive obsession? How can you fix it? |
All member variables of an object are instances of primitive types. Create "small classes" that can validate and enforce constraints. |
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What is wrong with Switch Statements? |
Exhibits a lack of understanding of polymorphism and encapsulation. |
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What is Speculative generality? |
- Adding features/classes because you might need to add something "someday" |
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What is a design pattern? |
A solution to a re-occuring design pattern |
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Describe the general format of a design pattern. |
1. Describe the problem and relevant context 2. Design solution 3. Design consequences, positive/negative impacts of solution on the system |
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What is the Composite Design pattern? |
Treat atomic elements and their components alike. |
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What is the intent and the applicability of the Composite Design? |
Intent: Treat individual objects and multiple, recursively-composed objects uniformly Applicability: - Objects must be composed recursively, - no distinction between individual - composed elements, objects in structure can be treated uniformly. |
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What some (3) effects/consequences of the Composite Design? Denote if they are positive or negative. |
+ Uniformity + Extensibility - Overhead |
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What is the Decorator Pattern? |
A transparent wrapper class. Extension by wrapping. |
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What is the intent and applicability of the decorator pattern? |
Intent: augment objects with new responsibilities Applicability: - when extension by subclassing is impractical - for responsibilities that can be withdrawn |
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What are the consequences of the decorator pattern? Denote if they are positive or negative. |
+ Responsibilities can be added/removed at run-time + avoid subclass explosion + recursive nesting allows multiple responsibilities - interface occlusion - split identity |
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What is the interpreter pattern? |
Provides a way to translate a language grammar into an object structure and to implement operations over that structure. |
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What is the visitor pattern? |
Encapsulate operations on the object structure as objects to allow easy addition of new operations without disturbing the classes implementing the object structure. |
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The Interpreter pattern builds on the _________ pattern. |
Composite |
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What is the Strategy Pattern's Intent and Applicability? |
Intent: Define a family of algorithms, encapsulate each one, and make them interchangeable Applicability: When an object should be configurable with one of several algorithm AND all algorithms can be encapsulated AND one interface covers all encapsulations |
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What are the consequences of the Strategy Pattern? |
+ Greater Flexibility and reuse + Can change algorithms dynamically - Strategy creation & communication overhead - Inflexible strategy interface |
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What is the difference between Factory Method and Abstract Factory? |
Factory method is just when there is a factory being called the client. Abstract Factory is where the client is not sure of the factory or the product being created. |
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What are the consequences of the Template Method? |
+ Inversion of control + promotes code reuse + Lets you enforce overriding rules - Must subclass to specialize behaviour |
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What are the pros and cons of Object Composition? |
+ provides a clean separation between components and interfaces + Allows for dynamic composition + Allows for flexible mixing/matching of features - forwarding - identity crisis - Fragementation |
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What are the pros and cons of Inheritance? |
+ No explicit forwarding - close coupling - static hierarchies - combinatorial explosion of features |
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What is an architecture pattern? |
A solution to a re-occurring architectural design problem |
