Download TDT4240 Software Architecture Exam Solutions: Architectural Concepts and Design and more Cheat Sheet Software Engineering in PDF only on Docsity!
Note! Students will find examination results at Studentweb. If you have questions regarding the results, you have to contact your department. Department of Computer and Information Science
SOLUTION for TDT4240 Software Architecture Exam
Academic contact during examination: Professor Alf Inge Wang Phone: +47 9228 9577 Examination date: Friday May 31s^2013 Examination time (from-to): 09:00 – 13: Permitted examination support material:
- IEEE (2000), "IEEE Recommended Practice for Architectural Description of Software- Intensive Systems", Software Engineering Standards Committee of the IEEE Computer Society.
- Kruchten, P. (1995), "The 4+1 View Model of Architecture", IEEE Software, 12(6).
- English-Norwegian dictionary (or to your native language if your not Norwegian) and/or an English thesaurus (English-English). Other information:
- Simple calculator or a calculator approved by NTNU allowed.
- The exam has 5 problems giving a total of 70 points. For each problem, each question has the same weight unless otherwise stated. The remaining 30 points are credits awarded from the software architecture project. Language: English (Answers can be given in Norwegian or English) Number of pages: 11
Page 2 of 11
Problem 1: Various questions (20 points)
Answer these questions briefly : 1.1 What is Bass, Clements and Kazman’s definition of Software Architecture (the definition in the textbook)? 1.2 What is idioms when we discussion terms related to design patterns? 1.3 Describe briefly the three types of view described in the textbook: Allocation, Component-and-Connector, and Module? 1.4 What is the purpose of a utility tree, and how is it used in an ATAM evaluation? 1.5 Which architectural view describes in detail how a module is coded? 1.6 Discuss whether this statement is true or false: “Every software system has a software architecture”. 1.7 Name one example of an architectural pattern that fits into the type module , one example that fits into the type component-and-connector , and one example that fits into the type allocation. 1.8 Give five reasons why software architecture is important according to the textbook. 1.9 Briefly explain how the four contexts Technical , Project life cycle , Business, and Professional affect the software architecture according to the textbook. 1.10 Write one fully specified quality attribute scenario for availability, using the template given in the textbook. 1.11 Describe the main types of availability tactics in the textbook, and give at least one specific example of an architectural tactic for each type. 1.12 Briefly explain the quality attribute interoperability. 1.13 Describe and explain the design pattern Abstract Factory using a class diagram. 1.14 What parameters (inputs) are typically used in models for analyzing performance? 1.15 What is an architectural pattern? 1.16 What analytic models are typically used for modeling availability? 1.17 What is a tradeoff point in an ATAM evaluation? 1.18 What is the challenge with a software product line where the scope is too narrow? 1.19 Briefly describe the steps in the Attribute-driven design method. 1.20 What techniques exist to help keep the code and the architecture consistent according to the textbook? References:
- Bass, Clements & Kazman: “Software Architecture in Practice”
- Coplien: “Software Design Patterns: Common Questions and Answers”
Page 4 of 11 1.12 Interoperability: The degree to which two ore more systems can usefully exchange meaningful information. 1.13 Abstract factory: A family of related classes can have different implementation details and through the abstract interface the client does not need to know anything about which variant it is us- ing.^23 Abstract Factory Structure <{Product}> Concrete product Factory Concrete factory Factory (^) <{Product}> interface AbstractFactory +createAbstractProduct:AbstractProduct interface AbstractProduct ConcreteFactory ConcreteProduct +createAbstractProduct:AbstractProduct 1.14 Parameters (inputs) for analytic modeling of performance (candidates): Arrival rate of events, queuing discipline, scheduling algorithm, service time for events, network topology, network band- width, routing algorithm etc. 1.15 Architectural pattern (candidate answers):
- Package of design decisions that is found repeatedly in practice
- Reusable structures that can be applied on construction of systems
- Defines the element types and their forms of interaction used in solving the problem. 1.16 Analytic models for availability: Markov models and statistical models. 1.17 Trade-off point in ATAM: An architectural decision that will affect two or more quality attrib- utes at the same time (both positive and negative effects) 1.18 Narrow scope in software product line: Too few variants of the product can be produced. 1.19 Attribute-driven design process:
- Choose the module to decompose 2 Refine the module: 2a) Choose architectural drivers 2b) Choose/create architectural pattern satisfying the drivers 2c) Instantiate modules and allocate functionality 2d) Define interfaces of the child modules 2e) Verify and refine use cases and quality scenarios 3 Repeat steps above for every module requiring further decomposition 1.20 Keep code and architecture consistent:
- Embedding the design in the code
- Frameworks
- Code templates
- Keeping code and architecture consistent by using tools, rules, mark out of date documents and schedule doc/code synchronization
Page 5 of 11
Problem 2: Choose the most appropriate architectural pattern (5 points)
Nominees: a) Layered b) Broker c) Model-view-controller d) Pipe-and-Filter e) Client-Server f) Peer-to-peer g) Service-Oriented h) Publish-Subscribe i) Map-Reduce j) Multi-tier Choose the most appropriate architectural pattern (one) for the 5 descriptions below. Motivate for your choices (give reasons for choosing the pattern):
- Wants to split a system into a number of computationally independent execution structures (groups of software and hardware) such as database, business logic, web interface and client, connected by some communication media. The structure is chosen to provide a specific server environment optimized for operational requirements and resource usage.
- Wants to set up a set of equal distributed computational entities that are connected via a common protocol to share their services and provide high availability and scalability.
- Wants a system that can be divided into reusable, loosely coupled components that can be flexibly combined and arranged to transform between various data formats.
- Wants a distributed system with a structure that enables that service users do not need to know the nature or location of service providers.
- Wants a system that quickly can analyze enormous volumes of data by sorting the data and then analyzing the grouped data.
Problem 3: Edge-‐dominant system (8 points)
a) What is an edge-dominant system and what characteristics do edge-dominant systems have? (2 points) b) Draw and explain the metropolis structure of an edge-dominant system (3 points) c) What are the implications of edge-dominant systems for the software architecture? (3 points)
Problem 4: Cloud Architecture (7 points)
a) Explain the three Cloud Service Models described in the textbook: 1) Software as a Service,
- Platform as a Service, and 3) Infrastructure as a Service (3 points) b) What are the economic benefits of using a cloud based architecture? (2 points) c) What is the purpose of the hypervisor in a cloud-based architecture? (2 points)
Page 7 of 11 Solution Problem 4 4a) Cloud Service Modes:
- Software as a Service (SaaS): Consumer uses applications running on a cloud.
- Platform as a Service (PaaS): Provides a development and deployment platform in the cloud.
- Infrastructure as a Service (IaaS): Provides a virtual machine for developer or system administrator. 4b) Economical benefits of using cloud-based architecture: Large data centers are cheaper (cost of power, infrastructure labor cost), security and reliably, hardware cost) Utilization of equipment (virtualization, adapt to time of day, year, usage patterns) Multi-tenancy: Single application used by multiple consumers saves costs related to user-support, simple upgrade, single version of software. 4c) Purpose of the hypervisor: Operating system to create and manage virtual machines. Manage a pool of hardware to provide an even larger pool of virtual machines through managing memory, processes, file access and network.
Page 8 of 11
Problem 5 Design a software architecture (30 points)
Read the description below and do an architectural design. Your answer must include: a) Architectural drivers – 2 points b) Architectural tactics and patterns – 3 points c) Process view – 8 points d) Logical view – 14 points e) Architectural rationale – 3 points Motivate for your choices and state your assumptions. Software for sea buoys support for navigation at sea There exists a collection of free-floating buoys that provide navigation and weather data to air and ship traffic at sea. The buoys collect air and water temperature, wind speed, and location data through a variety of sensors. Each buoy may have a different number of wind and temperature sensors and may be modified to support other types of sensors in the future. Each buoy is also equipped with a radio transmitter (to broadcast weather and location information as well as an SOS message) and a radio receiver (to receive requests from passing vessels. Some buoys are equipped with a red light, which may be activated by a passing vessel during sea-search operations. If a sailor is able to reach the buoy, he or she may flip a switch on the side of the buoy to initiate an SOS broadcast. Software for each buoy must:
- maintain current wind, temperature, and location information; wind speed readings are taken every 30 seconds, temperature readings every 10 seconds and location every 10 seconds; wind and temperature values are kept as a running average.
- broadcast current wind, temperature, and location information every 60 seconds.
- broadcast wind, temperature, and location information from the past 24 hours in response to requests from passing vessels; this takes priority over the periodic broadcast
- activate or deactivate the red light based upon a request from a passing vessel.
- continuously broadcast an SOS signal after a sailor engages the emergency switch; this signal takes priority over all other broadcasts and continues until reset by a passing vessel.
Page 10 of 11 TDT4240 Software Architecture 5c) Process view (there are several possible process view, but the view must show how the system is operating while running and how the different parts of the system interact). This process view shows an activity diagram with events and shows how the different parts of the system interact and that they all are timed by a clock, which outputs a pulse. The clock synchronizes all sensors as well as the broadcasting of messages. An SOS request triggered by the Emergency Switch will cause SOS Message send by the Radio Transmitter.
Page 11 of 11 TDT4240 Software Architecture 5d) Logical view 5e) Architectural rationale The architecture has focused on modifiability, performance and availability. The Clock provides both performance by scheduling when various tasks are performed, and is used as a heartbeat to check that the system is up and running (external hardware unit). Modifiability is provided through the Task Control Architecture pattern, which makes it easy to extend and change the design, clear separation of concerns between various parts, and abstraction for common services for sensors, which makes it easy to replace sensors as well as adding new sensors in the future.
