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Wagner, Stefan, PhD
Publications (5 of 5) Show all publications
Wagner, S., Fernández, D. M., Felderer, M., Vetrò, A., Kalinowski, M., Wieringa, R., . . . Winkler, D. (2019). Status quo in requirements engineering: A theory and a global family of surveys. ACM Transactions on Software Engineering and Methodology, 28(2), Article ID 9.
Open this publication in new window or tab >>Status quo in requirements engineering: A theory and a global family of surveys
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2019 (English)In: ACM Transactions on Software Engineering and Methodology, ISSN 1049-331X, E-ISSN 1557-7392, Vol. 28, no 2, article id 9Article in journal (Refereed) Published
Abstract [en]

Requirements Engineering (RE) has established itself as a software engineering discipline over the past decades. While researchers have been investigating the RE discipline with a plethora of empirical studies, attempts to systematically derive an empirical theory in context of the RE discipline have just recently been started. However, such a theory is needed if we are to define and motivate guidance in performing high quality RE research and practice. We aim at providing an empirical and externally valid foundation for a theory of RE practice, which helps software engineers establish effective and efficient RE processes in a problem-driven manner. We designed a survey instrument and an engineer-focused theory that was first piloted in Germany and, after making substantial modifications, has now been replicated in 10 countries worldwide. We have a theory in the form of a set of propositions inferred from our experiences and available studies, as well as the results from our pilot study in Germany. We evaluate the propositions with bootstrapped confidence intervals and derive potential explanations for the propositions. In this article, we report on the design of the family of surveys, its underlying theory, and the full results obtained from the replication studies conducted in 10 countries with participants from 228 organisations. Our results represent a substantial step forward towards developing an empirical theory of RE practice. The results reveal, for example, that there are no strong differences between organisations in different countries and regions, that interviews, facilitated meetings and prototyping are the most used elicitation techniques, that requirements are often documented textually, that traces between requirements and code or design documents are common, that requirements specifications themselves are rarely changed and that requirements engineering (process) improvement endeavours are mostly internally driven. Our study establishes a theory that can be used as starting point for many further studies for more detailed investigations. Practitioners can use the results as theory-supported guidance on selecting suitable RE methods and techniques. © 2019 Copyright held by the owner/author(s). Publication rights licensed to ACM.

Place, publisher, year, edition, pages
Association for Computing Machinery, 2019
Keywords
Replication, Requirements engineering, Survey research, Theory, Software engineering, Confidence interval, Elicitation techniques, Engineering disciplines, Requirements specifications, Survey instruments, Surveys
National Category
Software Engineering
Identifiers
urn:nbn:se:bth-17731 (URN)10.1145/3306607 (DOI)2-s2.0-85062345543 (Scopus ID)
Available from: 2019-03-21 Created: 2019-03-21 Last updated: 2019-03-25Bibliographically approved
Wagner, S. (2018). Extending characters of fixed point algebras. Axioms, 7(4), Article ID 79.
Open this publication in new window or tab >>Extending characters of fixed point algebras
2018 (English)In: Axioms, ISSN 2075-1680, Vol. 7, no 4, article id 79Article in journal (Refereed) Published
Abstract [en]

A dynamical system is a triple (A, G, α) consisting of a unital locally convex algebra A, a topological group G, and a group homomorphism α: G → Aut(A) that induces a continuous action of G on A. Furthermore, a unital locally convex algebra A is called a continuous inverse algebra, or CIA for short, if its group of units A× is open in A and the inversion map i: A× → A×, a → a-1 is continuous at 1A. Given a dynamical system (A, G, α) with a complete commutative CIA A and a compact group G, we show that each character of the corresponding fixed point algebra can be extended to a character of A. © 2018 by the authors.

Place, publisher, year, edition, pages
MDPI AG, 2018
Keywords
Character, Continuous inverse algebra, Dynamical system, Extension, Fixed point algebra, Maximal ideal
National Category
Algebra and Logic
Identifiers
urn:nbn:se:bth-17355 (URN)10.3390/axioms7040079 (DOI)000456944400011 ()2-s2.0-85056790615 (Scopus ID)
Note

open access

Available from: 2018-11-29 Created: 2018-11-29 Last updated: 2019-02-21
Schwieger, K. & Wagner, S. (2017). Part III, Free Actions of Compact Quantum Groups on C*-Algebras. SIGMA. Symmetry, Integrability and Geometry, 13, Article ID 62.
Open this publication in new window or tab >>Part III, Free Actions of Compact Quantum Groups on C*-Algebras
2017 (English)In: SIGMA. Symmetry, Integrability and Geometry, ISSN 1815-0659, E-ISSN 1815-0659, Vol. 13, article id 62Article in journal (Refereed) Published
Abstract [en]

We study and classify free actions of compact quantum groups on unital C*-algebras in terms of generalized factor systems. Moreover, we use these factor systems to show that all finite coverings of irrational rotation C*-algebras are cleft.

Place, publisher, year, edition, pages
NATL ACAD SCI UKRAINE, INST MATH, 2017
Keywords
free action, C*-algebra, quantum group, factor system, finite covering
National Category
Algebra and Logic
Identifiers
urn:nbn:se:bth-15088 (URN)10.3842/SIGMA.2017.062 (DOI)000407251200001 ()
Note

Open Access

Available from: 2017-08-31 Created: 2017-08-31 Last updated: 2017-09-08Bibliographically approved
Wagner, S. & Schwieger, K. Noncommutative Coverings of Quantum Tori. Mathematica Scandinavica
Open this publication in new window or tab >>Noncommutative Coverings of Quantum Tori
(English)In: Mathematica Scandinavica, ISSN 0025-5521, E-ISSN 1903-1807Article in journal (Other academic) Accepted
Abstract [en]

We investigate a framework for coverings of noncommutative spaces. Furthermore, we study noncommutative coverings of irrational quantum tori and characterize all such coverings that are connected in a reasonable sense.

Keywords
Free action, noncommutative covering, fundamental group, quantum tori, gauge action, connected, Bogoliubov transformation, Schrödinger representation
National Category
Mathematics Algebra and Logic
Identifiers
urn:nbn:se:bth-17514 (URN)
Funder
Carl Tryggers foundation , CTS16:540
Available from: 2019-01-24 Created: 2019-01-24 Last updated: 2019-01-25Bibliographically approved
Wagner, S. Secondary Characteristic Classes of Lie Algebra Extensions.
Open this publication in new window or tab >>Secondary Characteristic Classes of Lie Algebra Extensions
(English)In: Article in journal (Other academic) Accepted
Abstract [en]

We introduce a notion of secondary characteristic classes of Lie algebra extensions. As a spin-off of our construction we obtain a new proof of Lecomte’s generalization of the Chern–Weil homomorphism.

Keywords
Secondary characteristic class, Lie algebra extension
National Category
Mathematics Algebra and Logic
Identifiers
urn:nbn:se:bth-17519 (URN)
Funder
Carl Tryggers foundation , CTS16:540
Available from: 2019-01-24 Created: 2019-01-24 Last updated: 2019-01-25Bibliographically approved
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