| 1. |
- Grindal, Mats, et al.
(författare)
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An Evaluation of Combination Strategies for Test Case Selection
- 2006
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Ingår i: Empirical Software Engineering. - : Springer. - 1382-3256 .- 1573-7616. ; 11:4, s. 583-611
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents results from a comparative evaluation of five combination strategies. Combination strategies are test case selection methods that combine “interesting” values of the input parameters of a test subject to form test cases. This research comparatively evaluated five combination strategies; the All Combination strategy (AC), the Each Choice strategy (EC), the Base Choice strategy (BC), Orthogonal Arrays (OA) and the algorithm from the Automatic Efficient Test Generator (AETG). AC satisfies n-wise coverage, EC and BC satisfy 1-wise coverage, and OA and AETG satisfy pair-wise coverage. The All Combinations strategy was used as a “gold standard” strategy; it subsumes the others but is usually too expensive for practical use. The others were used in an experiment that used five programs seeded with 128 faults. The combination strategies were evaluated with respect to the number of test cases, the number of faults found, failure size, and number of decisions covered. The strategy that requires the least number of tests, Each Choice, found the smallest number of faults. Although the Base Choice strategy requires fewer test cases than Orthogonal Arrays and AETG, it found as many faults. Analysis also shows some properties of the combination strategies that appear significant. The two most important results are that the Each Choice strategy is unpredictable in terms of which faults will be revealed, possibly indicating that faults are found by chance, and that the Base Choice and the pair-wise combination strategies to some extent target different types of faults.
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| 2. |
- Mathiason, Gunnar
(författare)
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Virtual Full Replication for Scalable Distributed Real-Time Databases (Thesis Proposal)
- 2006
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Distributed real-time systems increase in size an complexity, and the nodes in such systems become difficult to implement and test. In particular, communication for synchronization of shared information in groups of nodes becomes complex to manage. Several authors have proposed to using a distributed database as a communication subsystem to offload database applications from explicit communication. This lets the task for information dissemination be done by the replication mechanisms of the database. With increasingly larger systems, however, there is a need for managing the scalability for such database approach. Furthermore, timeliness for database clients requires predictable resource usage, and scalability requires bounded resource usage in the database system. Thus, predictable resource management is an essential function for realizing timeliness in a large scale setting. We discuss scalability problems and methods for distributed real-time databases in the context of the DeeDS database prototype. Here, all transactions can be executed timely at the local node due to main memory residence, full replication and detached replication of updates. Full replication contributes to timeliness and availability, but has a high cost in excessive usage of bandwidth, storage, and processing, in sending all updates to all nodes regardless of updates will be used there or not. In particular, unbounded resource usage is an obstacle for building large scale distributed databases. For many application scenarios it can be assumed that most of the database is shared by only a limited number of nodes. Under this assumption it is reasonable to believe that the degree of replication can be bounded, so that a bound also can be set on resource usage. The thesis proposal identifies and elaborates research problems for bounding resource usage in large scale distributed real-time databases. One objective is to bound resource usage by taking advantages of pre-specified data needs, but also by detecting unspecified data needs and adapting resource management accordingly. We elaborate and evaluate the concept of virtual full replication, which provides an image of a fully replicated database to database clients. It makes data objects available where needed, while fulfilling timeliness and consistency requirements on the data. In the first part of our work, virtual full replication makes data available where needed by taking advantages of pre-specified data accesses to the distributed database. For hard real-time systems, the required data accesses are usually known since such systems need to be well specified to guarantee timeliness. However, there are many applications where a specification of data accesses can not be done before execution. The second part of our work extends virtual full replication to be used with such applications. By detecting new and changed data accesses during execution and adapt database replication, virtual full replication can continuously provide the image of full replication while preserving scalability. One of the objective of the thesis work is to quantify scalability in the database context, so that actual benefits and achievements can be evaluated. Further, we find out the conditions for setting bounds on resource usage for scalability, under both static and dynamic data requirements.
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| 3. |
- Olson, Maria, 1969-
(författare)
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Equivalence and the challenge of 'freedom of choice' - Consequences of a changed Policy on a Democratic Citizenship in Sweden
- 2006
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Ingår i: Enacting equity in education. - Helsinki : Research Centre for Social Studies Education, University of Helsinki. - 9521031964 - 9521031999 - 9789521031960 ; , s. 156-175
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Equivalence is regarded as a central concept in contemporary Swedish education policy. One important aspect in the education policy is to describe and determine the Swedish schools' assignment to bring up democratic citizens. The concept of equivalence, hence, plays an important role in this policy-making practice. In the 1990s equivalence is challenged by another concept: 'freedom of choice'. Here some possible outcomes of a changed conceptual framework in the education policy are tried out, regarding the political understanding of a democratic citizenship. Three questions are pulled forth in order to carry out this aim. The challenge of 'freedom of choice' on equivalence contributes to a change in the political understanding of a democratic citizenship in Swedish education policy. A phenomenon that occurs in at least three aspects: the political participation (from co-acting to re-acting), the political activity (from directing to voting) and the political role of the citizen in society (from being a designer to a consumer).
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