Software Engineering BFH
Software Engineering BFH
Software Engineering BFH
Nenne 4 Requirements Engineering Schritte
- Requirements elicitation (herauspicken)
- Requirements analysis
- Requirements validation
- Requirements management
Structure of a Typical Requirements Document
- Preface
- Introduction
- Glossary
- User requirements definition
- System architecture
- System requirements specification
- System models
- Testing
- Appendices
- Index
Unterschied zwischen Wasserfall und V-Model
erweitert Wasserfall-Modell um Validierungsphasen
Nenne die 4 Kriterien eines Lastenhefts
- Musskriterien
- Sollkriterien
- Kannkriterien
- Abgrenzungskriterien
Quality and Verification:
What is a protection system and how does it work?
A system that runs paralles to an other (security relevant) system to execute a task if the main system fails. It does the same as the main system does but with other sensors, techniques and technologies.
Quality and Verification:
How to get a Reliable / Available system?
By:
- Fault avoidance:
- Development
- z.B. exeption handling, check inputs --> if(23:00){...
- Fault detection and removal
- Verification and Validation before the system goes live
- Testing
- Fault tolerance
- runtime techniques > ensure that the system faults do not result in errors
and that errors do not lead to system failures - Redundancy, protection systems
- runtime techniques > ensure that the system faults do not result in errors
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DU!
Weiterhin viel SPASS beim Lernen :-)
Quality and Verification:
What kind fo safety systems are there?
- Primary safety-critical systems:
- Direct
- Embedded sw-systems whose failure cause the hardware to fail and directy threaten people
- Secondary safety-critical systems:
- Indirect
- Systems whose failure results in faults in other systems and ....
Quality and Verification:
Explain:
- Hazard
- Accident
- Damage
- Hazard severity
- Hazard probability
- Risk
- Hazard: Condition with the condition for causing an accident: Failure of the sensor
- Accident (mishap): Unplanned event resulting in human death or injury of anyting: Overdose of Insulin
- Damage: Result of the Accident: Overdose could cause injury or death of patient
- Hazard severity: Assessment of the worst possible damage: Possibility of death > severity = very high
- Hazard probaility: Pobability of the hazard: Pobability of a sensor failure = low
- Risk: comparison of severity and probability: risk of an insulinoverdose is probably medium to low
Quality and Verification:
Safety Achievement:
- Hazard avoidance
- Design: Classes of hazard cannot arise
- Hazard detection and removal
- Design: Hazard are detected and removed
- Damage limitation
- Protection features that minimize the damage
Quality and Verification:
4 Steps to Safety specification (Safety Risk Management):
- Risk identification
- Risk assessment
- analize damage and hazard severity and probabilityof each possible accident
(injuries, cost etc...)
- analize damage and hazard severity and probabilityof each possible accident
- Risk treatment
- Risk monitoring and incident handling
Quality and Verification
How do you treat risks?
- avoidance: eliminate risks
- reduction: mitigate impact and/or probability
- sharing: outsource or insure against
- acceptance: incident plan (what if..)
Quality and Verification
Three possible exception handling stategies?
- Signal to a calling component
- Carry out some alternative processing
- Pass control to a runtime support system to handle the exception
Quality and Verification
What should you try to avoid or minimize to avoid error-prone constructs?
- Floating-point numbers (unprecise)
- Parallelism (timing errors)
- Out of memory (attempt to process too much data)
- Recursion: stack overflows
- Aliasing
Quality and Verification
Testing Process:
Quality and Verification:
What does the sw verification testing show?
- That the sw meets its requirements
- i.e. perfomrs correctly using a set of test cases
Quality and Verification:
What is defect testing
- The test cases are designed to expose defects.
- The inputs shall cause anaomalous behavior
- A successful test is a test that makes the system perfomr incorrectly
Quality and Verification:
What kind of development tests are there?
Unit testing (methods)
component testing (interfaces)
system testing (interaction)
Quality and Verification:
What is release testing?
The process of testing a system that is intended to use outside the development team.
Quality and Verification:
what is software inspection?
examining the source with the aim of discovering anomalies and defects
does not use execution of the system
May be applied on requirements, design, configuration, data, test data, etc...
Nenne 5 Typen von Software
- Betriebssysteme
- Micro Controller
- Application Software
- System Software
Welche zwei Software Produkttypen gibt es. Mit Beispielen
- Generische Produkte (BTS Build to Stock)
Beispiele:
PC software such as graphics programs
project management tools
CAD software
software for specific markets such as appointments systems for dentists.
- Customized Products (BTO Build to Order)
Beispiele:
embedded control systems
air traffic control software
traffic monitoring systems.
Nenne die 4 Software Engineering Activites
- Analyse und Spezifikation
- Entwicklung
- Validierung
- Evolution (Weiterentwicklung)
Was macht eine gute Software aus
Gute Software sollte die gewünschte Funktionalität und Leistung für den Benutzer liefern und sollte Wartbar, zuverlässig und nutzbar sein
Was sind die Kosten von Software Engineering
Rund 60% der Softwarekosten sind Entwicklungskosten, 40% testen die Kosten. Für kundenspezifische Software übersteigen Evolutionskosten oftmals die Entwicklungskosten.
Welchen Einfluss haben die Kosten auf die Software Entwicklung?
tbd
Aufgrund von welchen Faktoren werden die Software Engineering Methoden entschieden?
- Benutzeranforderungen
- Applikationstyp
- Hintergrund vom Entwicklerteam
Was ist der Unterschied zwischen Software Engineering und Computer Science?
Computer Science konzentriert sich auf Theorie und Grundlagen. Software Engineering beschäftigt sich mit den Praktiken Entwicklung und Bereitstellung von nützlicher Software.
Was ist der Unterschied zwischen System Engineering und Software Engineering?
Die Systemtechnik beschäftigt sich mit allen Aspekten der computergestützten Systementwicklung, einschließlich Hardware, Software und Verfahrenstechnik. Software Ingenieurwesen ist Teil dieses allgemeineren Prozesses.
Was sind die wichtigsten Herausforderungen für das Software-Engineering?
Umgang mit zunehmender Vielfalt, Forderungen nach reduzierten Lieferzeiten und Entwicklung vertrauenswürdiger Software.
Was sind die besten Software-Engineering-Techniken und Methoden?
Während alle Softwareprojekte professionell verwaltet und entwickelt werden müssen, sind verschiedene Techniken für verschiedene Systemarten geeignet. Zum Beispiel sollten Spiele immer mit einer Reihe von Prototypen entwickelt werden, während sicherheitskritische Steuersysteme eine komplette und analysierbare Spezifikation erfordern. Sie können also nicht sagen, dass eine Methode besser ist als eine andere.
Welche Unterschiede hat das Web für Software Engineering gemacht?
Das Web hat zur Verfügbarkeit von Software-Diensten geführt und die Möglichkeit, hochverteilte Service-basierte Systeme zu entwickeln. Die webbasierte Systementwicklung hat zu wichtigen Fortschritten in Programmiersprachen und Softwarewiederverwendung geführt.
Zeichne den Software Egineering Prozess
Weshalb ist die Entwicklung eines Software Produktes, welches alle Anforderungen erfüllen soll, so schwierig?
Weil das Finden und Spezifizieren aller Anforderungen eines System sehr schwierig ist und weitreichende Konsequenzen in die Entwicklung hat. Das Requirements Engineering Process ist dafür da um alle Anforderungen systematisch und umfassend zu finden und zu dokumentieren.
Welche Activities werden sind in allen Software Engineering Prozessen beinhaltet?
Analysis – investigating what the system should do;
Specification – defining what the system should do;
Design – defining the organization of the system;
Implementation – implementing the system;
Validation – checking that it does what the customer wants;
Evolution – changing the system in response to changing customer needs.
Requirements Engineering ist der Prozess um folgendes Festzulegen:
is the process of establishing
Die Dienste, die der Kunde von einem System benötigt und die Einschränkungen, unter denen sie arbeitet und entwickelt wird
Beschreibe den Plan Driven Process
Prozesse, bei denen alle Prozessaktivitäten geplant sind und Fortschritt wird an diesem Plan gemessen.
Beschreibe den Agile Process
Die Planung ist inkrementell und es ist einfacher, den Prozess zu ändern, um den sich ändernden Kundenanforderungen gerecht zu werden.
Requirements/Anforderungen im Requirements Engineering sind...
die Beschreibungen der Systemdienste und Einschränkungen, welche während des Requirements Engineering Prozesses bestummen werden.
Nenne die 3 Software Egnineering Process Models
Thewaterfallmodel
- Plan-driven model.
- Separate and distinct phases of specification and development.
Incrementaldevelopment
Specification, development and validation are interleaved.
May be plan-driven or agile.
Reuse-orientedsoftwareengineering
The system is assembled from existing components.
May be plan-driven or agile.
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Patterns: Disadvantages of Design Patterns
1.Do not lead to direct code reuse
2. Complex in nature
3. they are deceptively simple
4. they are validated by experince and discussion
What is Model-driven engineering
an approach to software development in which a system is represented as a set of models that can be automatically transformed to executable code.
What is sw architecture?
- A model that describes how the sw is organized as :
- a set of components
- which communicate with each other
When do we design the sw architecure and why? (architectural design process)
- early stage of system design process
- often parallel with spec activities
- link between RE and sw design --> based on / parallel with context and domain model
Different levels of abstraction?
- individual programs (and their components)
- complex enterprise systems --> composed of other systems, programs, components
- distributed over different computers
- owned by different companies
Use of Architectural Models (5)?
- Stakeholder communication
- sh can understand the system and discuss --> no confusing detail
- System analysis
- analysis if the system can meet it's nf requirements
- Project planning
- planning & assigning responsibilities / ressources
- planning the interfaces and integration
- Documentation
- Complet model that shows
- the differnt components in a system
- interfaces
- connections
- Complet model that shows
- Large-scale reuse
- Architecture may be reusable
- Generic product may be developed in form of a framework
Architectural Representation form? How?
- Block diagrams (entities, relationships) > boxes and lines
- very abstract
- For stakeholders and project planing
- Cons: no types of relationships and no properties
- very abstract
- UML
- structure: component, package, deployment D.
- behavior: activity D.
- interaction: communication D and interaction overview
- For discusion with impl team, detailed planning, Model-Driven Engineering
- Cons: high effort for creation & maintainance
What is architectural design?
- creative process
- depending on type of system
Which are the important question for the architectural design?
- How to decompose into modules?
- How to deploy on different machines?
- Control strategy?
- Is there a generic application architecture that can be used?
- Architectural patterns?
This has large impact on non fon-functional properties!
- ++ how to evaluate the arch. design?
- ++ how to document the architecture
Non-Functional Requirements in Architecture?
- Performance (localise critical operations and minimise communication)
- Security (Layered architecture with critical assets in the inner Layers)
- Safety (Localise safety-critical features in a small number of sub-systems)
- Availability (redundant components and mechanisms for fault tolerance)
- Maintainability (fine-grain, replacable components)
- Scalability (distributed architecture to have options for load balancing)
Name 5 important architectural patterns:
- MVC / MVP
- Layering
- Client-Server and P2P
- Repository
- Pipe and Filter
Application Type Architectures
Application Types?
- Data processing applications
- batch processing without user intervention
- Scientific computing (CERN, ATLAS...)
- batch processing without user intervention
- Event processing systems
- Actions of app depending on events from outside
- sensor networks(environment or patient health monitoring)
- Actions of app depending on events from outside
- Transaction processing applications
- Data-centered
- process user requests and update infos in db
- e-commerce, reservaton systems...
- Language processing systems
- Userinput in formal language is processed and interpreted
- Compilers, databases, command interpreters
- Userinput in formal language is processed and interpreted
Application Type Architectures
Example for Transaction processing system:
May be based on the Pipe & Filter Architecture Pattern
Application Type Architectures
Transaction Processing System Example 2:
May be based on a Layer Architecture Pattern
Application Type Architectures
Example for Web-based information Systems:
Web-Shop:
- UI > Web browser
- apspecific layer includes additional functionality > shoping cart
- add items in separate transactions
- pay for all together in a single transaction
- Often implemented as Multi-tier Client-Server Architecture
- Web Server: responsible for user communication with the UI (Browser = client)
- Application Server: responsible for application specific logig, info storage, retrieval request
- DB-Server: moves info to and from db and handles transaction management
Application Type Architectures
Example for Language Processing System:
tbd
Application Type Architectures
Example for Compiler Components
tbd
Application Type Architectures
Example for Repository Architecture for Language Processing
What are Frameworks?
- Combine architecture with (partial) implementation
- Component-based design
- Made of abstract and concrete classes and the interfaces between them
- Components are impolemented by:
- filing in the missing parts of the design
- by instantiaiting the abstract classes
- moderately large entities that can be reused
Difference between Framework and Library?
Library
- handle prticular task (XML parsing, error logging...)
Frameworks
- Most define the general controll flow / event handling
- include libraries
- Web-app framework: provide user session management, data storage, web page template system
- Desktop-app framework: ui and standard widgets
What kind of frameworks are there?
- System infrastructure f.
- development of system infrastructure(communications, user interfaces., compilers)
- Middleware integration f.
- component communication and information exchange
- Enterprise application f.
- development of business specific apps
Selecting right framework ist often a trade-off between:
maximizing reuse & maximizing flexibility
Pros - Cons of Frameworks?
Pro:
- Efficiency
- Security
- Expense
- Support
..tbc
Cons:
Security
Restrictions
Learning a framework, not a language
..tbc
IMPLEMENTATION:
What is Object-Orented Design?
Object-oriented design is the process of planning a system of interacting objects for the purpose of solving a software problem.
It is one approach to software design.
IMPLEMENTATION:
OOD Results:
- Use Cases (user interaction with the system)
- System Context (System boundaries, interfaces, main processes)
- System Architecture (components, functionalities, interfaces)
- detailed system design model
- class and relationship model of each component
- associations, aggregation, generalization
- interfaces and privatge methods, attributes
- following design gudelines and design patterns
- activity and sequence diagrams
- state diagram
- class and relationship model of each component
IMPLEMENTATION:
What are the inputs for a Prototype?
- All analysis
- design artifacts > architecture and design models
IMPLEMENTATION:
What are the 6 steps of the implementation process?=
- Set up the general structure
- translate architectureal components into packages, libraries or external projects
- Define public interfaces and classes
- Define internal interfaces and classes
- Implement class methods according to priority list (backlog)
- Integrate, test and deliver
- Change design models an previous implementation (refactoring) as necessary
IMPLEMENTATION:
How web techonologies work together:
Typical WAF Features (5):
- Security (Authentication)
- Dynamic web pages (Templates)
- Database support (storing & retrieving app state)
- Session management (manage sessions)
- User interaction
IMPLEMENTATION:
What is a Build Management for (z.B Apache Maven)?
It is about generating an executable:
- which source code in which version
- dependencies to external components
- build - compile and link all ressources
- run test cases
- distributed compilation
- produce different variants of the software
- debug, production
- may be integrated with a deployment system --> CI
IMPLEMENTATION
SCRUM: Roles (4):
- Product owner
- Scrum master
- Developer
- Customers, users and managers
IMPLEMENTATION
SCRUM: Artifacts (4):
- Product backlog
- Sprint backlog
- Burndown chart
- design models, code and project-relevant artifacts
IMPLEMENTATION
SCRUM: Meetings (6):
- Product planning
- Sprint planning
- Daily scrum
- Code review
- sprint review
- product / release review
IMPLEMENTATION
SCRUM: Product Owner:
- Represents Customer
- Part of the scurm-team
- Participates meetings
- Maintains /decides priority of features (customer value)
- Prepares Backlog
- Reviews delivered product
- Accountable for the succes and delivery
IMPLEMENTATION
SCRUM: Scrum Master
- supports devs
- coaches team
- ensures that team adheres to Scrum
- helps resolve blocking situations
- arranges meetings
- keeps track of the backlog
- protects the team from external distractions
- communication outside of the team
IMPLEMENTATION:
Open-Closed Design Principle?
- Classes should be open for extensions
- Classes should be closed for modifications
Welche Anforderung sollten Requirements erfüllen?
- COMPLETE --> Beschreibung ALLER Services vorhanden?
- CONSISTENT --> Keine Wiedersprüche
Requirements validation is the process of checking the requirements
for validity, consistency, completeness, realism and verifiability.
COPYRIGHT
What is protected by Copyright?
- every novel expression of an idea (=works)
COPYRIGHT
From which moment is a copyright valid and for how long?
From the instant it is created.
The Period is different. Depending on the country.
COPYRIGHT
What does Copyright mean?
- Onyl the creator owner may display, copy and commercially exploit the works.
- He or She only is allowed to create derivate works on it
- but others are allowed to create works based on the original if it is fundamentally different
- Copyright applies to the expression of an idea, not the idea itself
- Not for the algorithm but for that specific implementation
- Algorithm must be protected by a patent
