"How do I know what I have to do?": the role of the inquiry culture in requirements communication for distributed software development projects.
“How do I know what I have to do?”-
The Role of the Inquiry Culture
in Requirements Communication
for Distributed Software Development Projects
Siemens AG Austria, PSE
Siemens AG Austria, PSE
As software specifications for complex systems are practically
never 100% complete and consistent, the recipient of the
specification needs domain knowledge in order to decide which
parts of the system are specified clearly and which parts are
specified ambiguously and thus need inquiry to achieve a more
detailed specification. In this paper we classify 16 different
situations (states) of requirements communication and analyze,
based on a state diagram, how a mature inquiry culture can help to
initiate transitions from undesirable states into more desirable
states. In a case study the inquiry practices of a very large
software development organization are shown. Knowledge
networks within the organization play an important role in
building up a mature inquiry culture.
Categories and Subject Descriptors
D.2.1 [Software Engineering]: Requirements/Specification –
elicitation methods, methodology.
Management, Documentation, Human Factors.
Requirements communication, informal/formal communication,
inquiry culture, requirement interaction management, global
software development, state machine.
Requirements engineering is one of the most significant factors
having an impact on productivity in software development. The
most common factors of project failure are linked directly to the
quality of the requirements  and the maturity in requirements
communication. It is rarely because of one or two reasons that IT
projects fail, but rather because of unrealistic project goals, badly
defined requirements and unmanaged risks, poor communication
between customers and developers, as well as the inability to deal
with the project’s complexity .
As the importance of global software development is increasing,
additional challenges occur, such as reduced face-to-face
communication due to greater geographical distances, cultural
differences, as well as language and time-zone barriers. At the
same time the technical complexity of average projects is
increasing. Therefore it is necessary to establish a more
methodical procedure for
dealing with requirements
What features, then, should the perfect requirement specification
have? Should it be complete and consistent? Hence, it is
important to make a distinction between sufficiency and
completeness, because a set of descriptions can be sufficient
without being complete. Completeness may constitute a
disadvantage in terms of time and costs .
A practice-oriented specification is written bearing in mind the
domain as well as the project context and is supposed to be read
in the same domain and project context. As every person has a
different context, this may lead to misunderstandings (for details
of the cognitive knowledge processing see ).
Maintaining consistency at all times is not always possible due to
project complexity. On the other hand, consistency at all times
may be counterproductive . In many distributed projects it
is even desirable to have some inconsistency in order to enhance
teamwork and make possible a flow of information that might
have not come about otherwise .
Specifying software requirements is an activity that puts high
demands on communication and cooperation. More frequent
interaction among project members and between customers and
project members will lead to more trust, fewer conflicts and - most
important of all - to the successful hand-over of project
The common approach to high quality requirements takes into
consideration both formal
techniques , as well as their intelligent integration.
and informal specification
In this paper a classification of requirements communication
situations between a requirements Sender and requirements
Receiver is provided and strategies of how to achieve adequate
sufficiency/completeness and how to minimize inconsistencies
within the requirements are presented. The results of this paper
are based on informal interviews of experienced requirement
engineers, project managers, architects and designers, as well as
experienced and inexperienced developers and testers, and will be
Copyright is held by the author/owner(s).
ICSE’06, May 20–28, 2006, Shanghai, China.
the basis of structured interviews of these experts for a more
detailed research on the key issues of the inquiry culture.
The implementation of complex distributed software development
projects involves team members with a range of different skills
and responsibilities. The individual team members have their own
domain contexts and their own project contexts and therefore their
own views on the specified system. The typical project structure
includes about 30 project members and one project manager
(PM), software engineering architects, developers and testers
Figure 1: Requirement Communication takes place at and
among all levels of the project organization
The capability to communicate requirements without errors is an
essential challenge in the requirements process. Requirements
communication takes place at and among all levels of the project
organization (Fig.1). We call the one who knows about the
specification the Sender S and the one who receives the
specification the Receiver R. The upper end of each
communication arrow in Fig. 1 points to the Sender, the lower end
to the Receiver. The Sender S communicates the requirement
specification to the Receiver R. E.g. the Sender S is the architect
and the Receiver R is the developer.
One of the simplest software systems would be a system that has
just one input x and one output y. Every time the input x is entered
into the system a predefined y is the expected output (Fig.2). The
requirement specification for such a system would be quite
transparent: An input-output map like the one in Fig. 2 completely
and consistently defines the system behavior. For each x exactly
one y exists, which is the required output.
We use this transparent requirement visualization in our paper
also for complex systems, because it still helps to understand the
problems of requirements communication. In the case of a
requirements specification of a complex system, the points of the
input-output map are just abstract representations of requirements
regarding the desired system behavior (Fig. 3). The values
themselves have no numerical meaning but nevertheless show a
deviation from a desired behavior and the necessity of
“interpolating” incomplete or inconsistent requirements.
Figure 2: Simple System: For every input x the required
output y is clearly specified (completely and consistently)
Figure 3: Complex System: A set of requirements specify the
desired system behavior only incompletely and sometimes
inconsistently (Note that the third requirement shows an
inconsistency). The combination of domain and context
knowledge helps you to “interpolate” the missing details
For each requirement the Sender S of the requirement may be in
one of the four situations indicated below.
The requirement is correct and S is convinced that it is
The requirement is correct but S is not sure that it is
correct. S is not able to define it as final.
The requirement is incorrect but S is convinced that it
The requirement is incorrect and S knows that he is not
convinced that it is correct.
On the other hand, Receiver R may have to deal with the same
four situations for each requirement.
In order to help intuitive understanding, the abstract visualization
of these four situations shows not only the requirement according
to Fig. 3, but also the “absolute truth”, defined as the usually
unknown complete set of requirements, which would optimize the
system behavior of this specific project according to a certain
optimization criterion. A full circle denotes that Sender S is
convinced that his requirement is correct, while an empty circle
denotes that Sender S is not sure whether the requirement is
R1: R2: R3: R4:
1 2 3 4
5 6 7 8
9 10 11 12
13 14 15 16
Table 1: The 16 cases of requirements communication
Note that we distinguish between the words correct and valid. A
requirement can be officially considered as valid but nevertheless
it is incorrect in terms of the objective absolute truth.
The combinations of these situations lead us to 16 cases of
possible variations of requirements communication interaction
between Sender/Receiver (Tab.1 and Fig. 4).
3. INQUIRY PRACTICES
Before we start to discuss the 16 different cases, we present some
common practices of how inconsistencies and incompleteness are
cleared up within Siemens Program and System Engineering PSE,
a Siemens-in-house R&D division with 6200 engineers
distributed over 20 sites.
The first step for completing specifications or detecting
inconsistencies is to apply personal context knowledge and
common sense. If you have worked on previous projects with the
same customer, you already have some context knowledge
concerning this specific customer. By using common sense you
can detect and solve obvious inconsistencies in your software
requirement specification (e.g. requirement 3 in Fig. 3).
3.2 Domain Knowledge
The second step is to apply your personal domain knowledge.
In a figural sense the combination of the context knowledge and
the domain knowledge helps you to “interpolate” the details
between the explicitly specified requirements (compare Fig. 2 and
3.3 Inquiry within the Project Team (Peers)
If your personal context and domain knowledge is not sufficient
or if you wish to get another opinion concerning your problem,
you will ask other experienced colleagues in you project team.
3.4 Inquiry within the Organizational
Knowledge Networks of the Receiver
A main asset of organizations like PSE is the compounded
knowledge of all 6200 experts. An engineer of PSE may contact
the proper PSE Knowledge Network , consult one of the
internal consulting centers, i.e. PSE Support Centers , ask for
resources from the PSE Know-How Base - either locally within
his region or throughout the organization  - or he may post an
Urgent Request to all members of all PSE Knowledge
Networks . In other words, the engineer has direct access to
the knowledge of all experts within the organization and can
therefore complement the knowledge he himself lacks efficiently
3.5 Inquiry within the Project Hierarchy
The project manager tries to enable an open inquiry culture within
his project organization. The art of the project manager is to build
up an atmosphere in which every team member feels welcome to
ask questions . At the same time he “educates” the team
members to use the peer networks of the whole organization for
topics which can be more efficiently solved by them than by the
project hierarchy. This also educates the team members to build
up the competency to be able to ask mature questions.
3.6 Inquiry within the Knowledge Networks
of the Sender
If you have worked on several projects for the same customer, you
will usually have established personal networks with the
colleagues of the Sender. This gives you the opportunity to get the
missing project information through your informal networks.
3.7 Inquiry to the Sender
Depending on the type of missing or required information or the
type of inconsistency, it can be the first and natural step to ask the
Sender. In the first phases of the requirement definition it is
desirable that the Sender and Receiver communicate intensively,
because they have to speak in the same terminology.
During the project the Sender usually expects a more specific
communication and appreciates it if he is not involved in every
small detail but only in topics that are relevant from his point of
3.8 Inquiry to External Sources
If neither the Sender’s organization nor the Receiver’s
organization can provide the missing information, PSE may resort
to the network of external sources it has built up and which can
help in such cases .
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Figure 4: Visualization of a requirement space with 16
specified requirements corresponding to the 16 cases of Tab. 1.
The upper graph shows the personal view of the Sender , the
lower graph the personal view of the Receiver . Legend:
Requirement specification where the person is convinced that
it is correct; : Requirement specification where the person
is not convinced that it is correct; solid line: The unknown
invisible “absolute truth”.
4. STRATEGIES FOR THE 16 CASES
Each of the 16 cases (Tab. 1) describes a different situation, which
may occur when a requirement is communicated from the Sender
to the Receiver. According to Fig. 3 and Section 2 these 16 cases
are visualized in Fig. 4. The solid line shows the unknown
absolute truth of the customer needs, as defined in Section 2.
Case 1: The requirement was correct and was correctly
communicated. Hence, the Receiver R has the correct requirement
and is convinced that this requirement is correct (Fig. 4,
Requirement 1). No further action is required.
Case 2: The requirement was correct and was correctly
communicated. Nevertheless, the Receiver is not convinced that
this requirement is correct (Fig. 4, Requirement 2). It is the
responsibility of R to decide whether some further action is
required or whether, for reasons of efficiency, the (non-critical)
requirement is taken as it is. Usually, R tries to be convinced by
involving his team colleagues or his personal networks as
mentioned in Section 3.
Case 3: The requirement was correct, but the Receiver interpreted
the requirement incorrectly. Nevertheless, R is (wrongly)
convinced that the requirement is correct (Fig. 4, Requirement 3).
Intensive communication with the Receiver enables the Sender to
realize that the Receiver has misunderstood the specification and
to clarify matters. An intact communication within the team
enables R to realize that he has interpreted the requirement
incorrectly (Fig. 5).
Case 4: The requirement was correct and the Receiver interpreted
the requirement incorrectly, but he is not sure of his interpretation
(Fig. 4, Requirement 4). The Receiver knows that he must act by
using one of the inquiry practices of Section 3. The goal of this
activity is to change the state to Case 2 or even better to Case 1
Case 5: The requirement is correct, but the Sender is not
convinced that it is correct. Nevertheless, the Receiver
understands the requirement correctly and is convinced that the
requirement is correct (Fig. 4, Requirement 5). Due to his context
and/or domain knowledge he was able to ascertain the correctness
of the requirement. In the course of communication the Sender
may be convinced as well (Fig. 5).
Case 6: The requirement is correct but both the Sender and the
Receiver are not convinced that the requirement is correct. As
both have a different context and knowledge, the missing
information can be added by discussion to make sure that both
parties are convinced in the end. (Fig.5). Otherwise, both the
Sender and the Receiver may offer to involve their networks.
Case 7: The requirement was correct, but the Sender is not
convinced that it is correct. The Receiver interprets the
requirement incorrectly. Nevertheless, R is (wrongly) convinced
that the requirement is correct (Fig. 4, Requirement 3). The
strategy is similar to Case 3. The advantage of Case 7 is that the
uncertainty of the Sender may trigger a clarifying discussion
Case 8: The requirement was correct, but the Sender is not
convinced that it is correct. The Receiver interpreted the
requirement incorrectly but he is not convinced of his
interpretation (Fig. 4, Requirement 8). Like in Case 7 the Receiver
will implement a wrong requirement if no action is taken.
Therefore the Receiver uses one of the inquiry practices of
Section 3 (Fig. 5).
Case 9: The requirement is incorrect, but the Sender is (wrongly)
convinced that it is correct. The Receiver corrects the requirement
and is convinced that this is what the Sender really meant. It is the
responsibility of the Receiver to decide whether it is necessary to
convince the Sender or whether it is an uncritical requirement that
does not need to be corrected (Fig. 5).
Case 10: This case is similar to case 9 except that the Receiver is
not convinced that his proposed requirement is correct.
Case 11: The requirement is incorrect, but the Sender is
(wrongly) convinced that it is correct. The Receiver takes the
requirement as it is and is therefore wrongly convinced that the
requirement is correct (Fig. 4, Requirement 11). This is the most
dangerous situation between the Sender and the Receiver, as
neither can see the problem. If both have an adequate
communication culture within their teams, there is the chance that
one of them recognizes the mistake (Fig. 5).
Case 12: The requirement is incorrect, but the Sender is
(wrongly) convinced that it is correct. The Receiver understands
the requirement as it was communicated to him, but he is not
convinced that it is correct (Fig. 4, Requirement 12). The Receiver
is the only one who can change the state (Fig. 5), using the
methods described in Section 3.
Case 13: This case is similar to Case 9. The requirement is
incorrect, and the Sender is not convinced that it is correct. The
Receiver corrects the requirement and is convinced (Fig. 4,
Requirement 13) that his version of the requirement is what the
Sender really meant (Fig. 5).
Case 14: The requirement is incorrect and the Sender is not
convinced that it is correct (he feels that something is wrong). The
Receiver has corrected the requirement, but he is not convinced
that his proposed requirement is what the Sender really meant
(Fig. 4, Requirement 14). Again, the expertise of Sender and
Receiver can help to clear up this case (Fig. 5). Moreover, both
the Sender and the Receiver may involve their networks to get
additional information and views.
Case 15: The requirement is incorrect and the Sender is not
convinced that it is correct (he feels that something is wrong). If,
for some reason or other, the Sender tries to hide his uncertainty,
the Receiver might take the requirement to be correct and,
therefore, will implement this wrong requirement if no action is
taken. As R is (wrongly) convinced that the requirement is correct,
he will not be the one to initiate any action (Fig. 4,
Requirement 15). Although it is the responsibility of the Sender to
inform the Receiver of his doubt, an intact communication within
the team of the Receiver can help to recognize the mistake
(Fig. 5). However, an intact partnership between Sender and
Receiver would provide an open communication between them
and prevent information hiding.
Case 16: The requirement is incorrect, and the Sender is not
convinced that it is correct (he feels again that something is
wrong). The Receiver is not able to correct the requirement on his
own, but at least he is not convinced either that the requirement is
correct (Fig. 4, Requirement 16). This is a dangerous situation for
the project, if none of the two parties reacts properly.
Nevertheless, Case 16 is less dangerous than Case 11, as both are
aware of their uncertainty. Again, the different views of Sender
and Receiver can help to clarify this case. If not, both the Sender
and the Receiver may involve their networks for additional
support and thus arrive at a more desirable state (Fig. 5).
4.1 State Transitions
The description of these 16 cases presents all possible situations
between the Sender and Receiver. Without loss of generality we
assumed that the set of requirements remain constant during the
project. In other words, the continuous line in Fig. 4 and the
continuous line of the state visualizations in Fig.5, called absolute
truth remains constant. This is not the case in all projects. Note
that a change of the absolute truth without the knowledge of
Sender and Receiver is an unrecognized transition from State 1 to
State 11. As explained in Case 11, it is much more likely to detect
such a situation if at least one of the two parties, either the Sender
or the Receiver, recognizes this situation (State 12 or State 15). In
all 3 cases a mature communication and inquiry culture helps to
avoid severe problems for the project. The most dangerous cases
occur if no communication action is taken (Fig. 5).
Note that some states need a longer path for transition to a highly
desirable state: e.g.: a typical path from State 16 to State 1 would
follow the states 16 →14 → 13 → 5 → 1.
communication cases (states) according to Tab. 1. Without a
proper inquiry culture 50% of the states remain in an
undesirable state. Legend:
inquiry; : state transition which may cause severe
problems for the project;
(For details see the case description in Section 4.)
State diagram of the 16 requirements
: state transition by an
: other state transitions.
In this paper we have presented the virtual requirements
communication state machine which, in a mature customer-
developer partnership usually operates on an unconscious level.
The goal of this research is to get more insight into, as well as
reproducibility and consciousness
communication-based requirements techniques.
of these informal
Today professional software development without processes is
unimaginable, but also software development without integration
of informal requirements techniques will result in severe
efficiency problems. The goal of our work is to integrate the
inquiry culture into the software development processes and to
find ways for stimulating the inquiry culture until it becomes a
living culture in organizations.
We demonstrated that a missing inquiry culture may cause the
implementation of requirements which do not satisfy the
customer’s needs. It will require additional money, time, and
resources to mend matters, and it will lead to a loss of reputation.
Until now our research has been based on informal interviews
within PSE organizations in 9 different countries. Based on the
presented classification, we plan structured interviews for a more
detailed insight into and a more validated knowledge of the key
issues of inquiry culture.
Open issues: We assume the existence of an “absolute truth”. We
state that the absolute truth is neither known by the Sender nor by
the Receiver, and it is even imaginable that it does not exist
objectively. One reason could be that both the Sender’s view and
the Receiver’s view equally fulfill the optimization criterion.
Is it conceivable that, during a project, the Sender and the
Receiver classify each requirement according to the 16 cases of
Fig. 5? In this case they cannot classify it based on the absolute
truth but only on their personal opinion of what this truth is. Up to
now we have not analyzed whether this approach is practicable
and has enough impact on a project.
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