Requirements engineering (RE) is a systematic approach to articulating an explicit requirements specification agreed upon by stakeholders, incorporating phases such as elicitation, analysis, specification, and validation. Challenges in RE include incomplete requirements, communication flaws, and changing goals, which complicate successful requirements measurement. Requirements management (RM) complements RE by managing the entire software lifecycle's requirements, including documentation, change management, and traceability.

1. Introduction to RE:
Requirements
Engineering
CECS 542
Photo credit: Alberto Res1fo, Unsplash
Dr. habil. Birgit Penzenstadler, CSULB

2. Contributors
Earlier edi1ons of these slide sets have in part
been contributed to by:
• Dr. habil. Daniel Méndez Fernández
• Prof. Dr. Dr. h.c. Manfred Broy
• Prof. Dr. Stefan Wagner
• Prof. Dr. Marco Kuhrmann
I would like to thank you for our past and
present collabora1ons.

3. Dr. Birgit Penzenstadler
Intro to RE
CSULB spring 2017 12

4. What is Requirements Engineering?
Dr. Birgit Penzenstadler 13
• Def.: Requirements Engineering (RE) denotes the
itera1ve, systema1c, efficient and effec1ve approach
to elabora1ng an explicit requirements specifica1on
that is agreed upon by all stakeholders.
• It includes the major phases of
1. Elicita1on
2. Analysis
3. Specifica1on
4. Valida1on & Verifica1on
– Development is itera&ve
– Phases are recurring
(req. and architecture co-development)

5. Mo1va1on
These guys want a webpage:
“We dig holes”
www.youtube.com/watch?v=V8AoWTK0itQ
What requirements do they have?
Dr. Birgit Penzenstadler 14

6. Discussion
• Why is RE important?
• What are challenges in requirements
engineering?
• What are problems in RE?
Dr. Birgit Penzenstadler 15

7. Problems in RE*
1. Incomplete and / or hidden requirements
2. Inconsistent requirements
3. Terminological problems
4. Unclear responsibili1es
5. Communica1on flaws within project teams and with customers
6. Moving targets (changing goals, business processes and / or
requirements)
7. Technically unfeasible requirements
8. Stakeholders with difficul1es in separa1ng requirements from previously
known solu1on designs
9. Underspecified requirements that are too abstract and allow for various
interpreta1ons
10. Unclear / unmeasurable non-func1onal requirements
Challenge: successful RE is hard to measure
Dr. Birgit Penzenstadler 16
* Acc. to a study by Mendez 2012

8. This is our mo1va1on

9. Defini1ons
• What is a Requirement?
• RE und RM
• RE in the process
Dr. Birgit Penzenstadler 18

10. What is a Requirement?
• Def.: A requirement is
1. a constraint/ability/characteris1c that a
stakeholder requires for a product or process in
order to solve a problem or reach a goal.
2. a constraint/ability/characteris1c that a system
has to sa1sfy in order to fulfill a contract, a
standard, a specifica1on or other given formal
documents.
3. a documented representa1on of a constraint/
ability/characteris1c as defined in 1. or 2.
Dr. Birgit Penzenstadler 19
Source: IEEE-Standard, Std. 610.12-1990 [IEEE610.12.1990]

11. Requirements Management and RE
Recap: RE is the approach to elabora1ng a
requirements specifica1on agreed by stakeholders.
Def.: Requirements Management (RM) efficiently
and effec1vely manages the elabora1on and usage
of requirements in the whole sowware lifecycle.
RM includes ac1vi1es from project management:
• Budget calcula1on, risk management, planning, ...
• Project control: Incremental development, 1me boxing, ...
Dr. Birgit Penzenstadler 20

12. Tasks in Requirements Management
• Administra1on of requirements
• Structuring, documen1ng and archiving
• A^ribu1on of requirements
• Ra1onale management and traceability
• Jus1fica1on of requirements
• Linking in between requirements and to documenta1on artefacts
• Valida1on and verifica1on
• Change management including impact analysis
• Version management and configura1on management
• Claim management
• Support for distributed RE
• Tool support
Dr. Birgit Penzenstadler 21