1. Requirement Engineer Terms and Conditions
General Review
Requirement Engineer Terms and Conditions

2. Requirements Engineering
Main issues:
• What do we want to build
• How do we write this down
SE, Requirements Engineering, Hans van Vliet, ©2007
© SE;P&P, Hans van Vliet

3. Requirements Engineering
the first step in finding a solution for a data processing problem
the results of requirements engineering is a requirements specification
requirements specification
contract for the customer
starting point for design
Important issues here:
different stakeholders and their respective languages
the user often represents an unfamiliar domain
the user is not able to express his real problem
SE, Requirements Engineering, Hans van Vliet, ©2007
© SE;P&P, Hans van Vliet

4. Requirements engineering, main steps
1. understanding the problem: elicitation 2. describing the problem: specification 3. agreeing upon the nature of the problem: validation 4. agreeing upon the boundaries of the problem: negotiation This is an iterative process
SE, Requirements Engineering, Hans van Vliet, ©2007
© SE;P&P, Hans van Vliet

5. Framework for RE process
specification
elicitation
validation
doc & mgt
negotiation
SE, Requirements Engineering, Hans van Vliet, ©2007

6. Requirements engineering is difficult
Success depends on the degree with which we manage to properly describe the system desired
This is an example forma (real) library project.
One of the requirements was to devise a format for the library records, with fields like author(s), title, isbn, etc.
Quite a while later, we learned that there had to be 2 author fields: one for the author as it appears on the book, and one for the so-called canonical author name. The Russian author named “Chekhov” is written as “Tsjechow” in Dutch. In a (Dutch) search for book written by “Tsjechow”, we would like to get the English titles as well.
Library employees know this. It is tacit knowledge. They learn this during their first year of their study for librarian. I thought I knew libraries. After all, I've been there quite often.
SE, Requirements Engineering, Hans van Vliet, ©2007
© SE;P&P, Hans van Vliet

7. SE, Requirements Engineering, Hans van Vliet, ©2007
how do you handle conflicts during requirements engineering?
- try to take a middle road and satisfy everyone, a bit
- choose for one party
- talk until everyone agrees to one particular solution
- vote
- build in everything
SE, Requirements Engineering, Hans van Vliet, ©2007
© SE;P&P, Hans van Vliet

8. How we study the world around us
people have a set of assumptions about a topic they study
this set of assumptions concerns:
how knowledge is gathered
how the world is organized
SE, Requirements Engineering, Hans van Vliet, ©2007
© SE;P&P, Hans van Vliet

9. Elicitation techniques
Interview
brainstorming session
task analysis
scenario analysis
ethnography
form analysis
analysis of natural language descriptions
domain analysis
Business Process Redesign (BPR)
prototyping
SE, Requirements Engineering, Hans van Vliet, ©2007

10. Requirements are descriptions of the services that a software system must provide and the constraints under which it must operate Requirements can range from high-level abstract statements of services or system constraints to detailed mathematical functional specifications
Requirements Engineering is the process of establishing the services that the customer requires from the system and the constraints under which it is to be developed and operated

11. Types of Requirement More reference
User requirements
Statements in natural language plus diagrams of the services that the systems provides and its operational constraints. Written for customers
System requirements A structured document setting out detailed descriptions of the system services Written as a contract between client and contractor.

12. Software specification
A detailed software description which can serve as a basis for a design or implementation. Written for developer.

13. Example Definition and specifications User Requirements
Definition: The software must provide a means of representing and accessing external files created by other tools System Requirements specification:
يجب أن يوفر البرنامج وسيلة لتمثيل والوصول إلى الملفات الخارجية التي تم إنشاؤها بواسطة الآخرين
CS2 Software Engineering note 2 CS2Ah Autumn 2004

14. The user should be provided with facilities to define the type of external files Each external file type may have an associated tool which may be applied to the file Each external file type may be represented as a specific icon on the user’s display

15. Facilities should be provided for the icon representing an external file to be defined by the user
When a user selects an icon representing an external file, the effect of that selection is to apply the tool associated with the type of external file to the file represented by the selected icons