Diese Anleitung beschreibt die Grundlagen der Erstellung von problembasierten Prufungsfragen fur den ICT‐Unterricht. Sie enthalt Informationen zum Fragenaufbau, beschreibt die verschiedenen von SIOUX unterstutzten Fragetypen und veranschaulicht die haufigsten Fehler beim Fragendesign. Abschliessend werden die Grundzuge der Item‐Analyse an einem konkreten Beispiel erlautert.
{"title":"Anleitung zur Erstellung von problembasierten Prüfungsfragen für den ICT-Unterricht","authors":"Markus Dahinden","doi":"10.3929/ETHZ-A-00690999","DOIUrl":"https://doi.org/10.3929/ETHZ-A-00690999","url":null,"abstract":"Diese Anleitung beschreibt die Grundlagen der Erstellung von problembasierten Prufungsfragen fur den ICT‐Unterricht. Sie enthalt Informationen zum Fragenaufbau, beschreibt die verschiedenen von SIOUX unterstutzten Fragetypen und veranschaulicht die haufigsten Fehler beim Fragendesign. Abschliessend werden die Grundzuge der Item‐Analyse an einem konkreten Beispiel erlautert.","PeriodicalId":10841,"journal":{"name":"CTIT technical reports series","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2010-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76541632","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-01-01DOI: 10.3929/ETHZ-A-006902867
Y. Disser, Matúš Mihalák, P. Widmayer
We consider a simple agent exploring a polygon by moving from vertex to vertex along the boundary. At every vertex, the agent observes all angles between pairs of edges of the visibility graph, i.e. the angle between all pairs of visible vertices. The goal of the agent is to reconstruct the shape of the polygon, or equivalently its visibility graph. A polynomial time algorithm exists if the agent knows the total number of vertices a priori. We adapt this algorithm to work even if the number of vertices is not known beforehand.
{"title":"Reconstruction of a polygon from angles without prior knowledge of the size","authors":"Y. Disser, Matúš Mihalák, P. Widmayer","doi":"10.3929/ETHZ-A-006902867","DOIUrl":"https://doi.org/10.3929/ETHZ-A-006902867","url":null,"abstract":"We consider a simple agent exploring a polygon by moving from vertex to vertex along the boundary. At every vertex, the agent observes all angles between pairs of edges of the visibility graph, i.e. the angle between all pairs of visible vertices. The goal of the agent is to reconstruct the shape of the polygon, or equivalently its visibility graph. A polynomial time algorithm exists if the agent knows the total number of vertices a priori. We adapt this algorithm to work even if the number of vertices is not known beforehand.","PeriodicalId":10841,"journal":{"name":"CTIT technical reports series","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2010-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87996088","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-01-01DOI: 10.3929/ETHZ-A-006875053
Tobias Mömke
The metric traveling salesman problem is one of the most prominent APX-complete optimization problems. An important particularity of this problem is that there is a large gap between the known upper bound and lower bound on the approximability (assuming P 6= NP ). In fact, despite more than 30 years of research, no one could find a better approximation algorithm than the 1.5-approximation provided by Christofides. The situation is similar for a related problem, the metric Hamiltonian path problem, where the start and the end of the path are prespecified: the best approximation ratio up to date is 5/3 by an algorithm presented by Hoogeveen almost 20 years ago. In this paper, we provide a tight analysis of the combined outcome of both algorithms. This analysis reveals that the sets of the hardest input instances of both problems are disjoint in the sense that any input is guaranteed to allow at least one of the two algorithms to achieve a significantly improved approximation ratio. In particular, we show that any input instance that leads to a 5/3-approximation with Hoogeveen’s algorithm enables us to find an optimal solution for the traveling salesman problem. This way, we determine a set S of possible pairs of approximation ratios. Furthermore, for any input we can identify one pair of approximation ratios within S that forms an upper bound on the achieved approximation ratios.
{"title":"Structural properties of hard metric TSP inputs","authors":"Tobias Mömke","doi":"10.3929/ETHZ-A-006875053","DOIUrl":"https://doi.org/10.3929/ETHZ-A-006875053","url":null,"abstract":"The metric traveling salesman problem is one of the most prominent APX-complete optimization problems. An important particularity of this problem is that there is a large gap between the known upper bound and lower bound on the approximability (assuming P 6= NP ). In fact, despite more than 30 years of research, no one could find a better approximation algorithm than the 1.5-approximation provided by Christofides. The situation is similar for a related problem, the metric Hamiltonian path problem, where the start and the end of the path are prespecified: the best approximation ratio up to date is 5/3 by an algorithm presented by Hoogeveen almost 20 years ago. In this paper, we provide a tight analysis of the combined outcome of both algorithms. This analysis reveals that the sets of the hardest input instances of both problems are disjoint in the sense that any input is guaranteed to allow at least one of the two algorithms to achieve a significantly improved approximation ratio. In particular, we show that any input instance that leads to a 5/3-approximation with Hoogeveen’s algorithm enables us to find an optimal solution for the traveling salesman problem. This way, we determine a set S of possible pairs of approximation ratios. Furthermore, for any input we can identify one pair of approximation ratios within S that forms an upper bound on the achieved approximation ratios.","PeriodicalId":10841,"journal":{"name":"CTIT technical reports series","volume":"99 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2010-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76985256","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-01-01DOI: 10.3929/ETHZ-A-006904372
Alexander J. Summers, Peter Müller
Null pointer dereferences are the most common runtime error in languages such as Java and C#. To alleviate this problem, Fahndrich and Leino proposed a non-null type system, in which reference types can be annotated with non-nullity expectations that are statically enforced. The main challenge for the static checking of non-nullity is object initialisation; since fields of new objects get first initialised with null, a non-null type system needs to determine when an object is fully initialised and, thus, its non-null fields actually contain non-null values. Several proposed solutions exist for tackling this problem, but each fail on one of the three criteria of soundness, flexibility and simplicity. In this paper we present a solution which satisfies all three criteria, making it suitable for mainstream use. We provide a formalisation of the core type system and prove soundness for a small language. We also show informally how the core type system can be extended to support a realistic language.
{"title":"Freedom before commitment","authors":"Alexander J. Summers, Peter Müller","doi":"10.3929/ETHZ-A-006904372","DOIUrl":"https://doi.org/10.3929/ETHZ-A-006904372","url":null,"abstract":"Null pointer dereferences are the most common runtime error in languages such as Java and C#. To alleviate this problem, Fahndrich and Leino proposed a non-null type system, in which reference types can be annotated with non-nullity expectations that are statically enforced. The main challenge for the static checking of non-nullity is object initialisation; since fields of new objects get first initialised with null, a non-null type system needs to determine when an object is fully initialised and, thus, its non-null fields actually contain non-null values. Several proposed solutions exist for tackling this problem, but each fail on one of the three criteria of soundness, flexibility and simplicity. In this paper we present a solution which satisfies all three criteria, making it suitable for mainstream use. We provide a formalisation of the core type system and prove soundness for a small language. We also show informally how the core type system can be extended to support a realistic language.","PeriodicalId":10841,"journal":{"name":"CTIT technical reports series","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2010-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88242339","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-01-01DOI: 10.2749/222137810796024628
Mattias Nilsson, K. Eriksson, G. James, P. Collin
Numerous cracks have been discovered in the Varby Bridge near Stockholm, Sweden. All cracks are found at the junctions between the cross girders and the main girders, more specifically, at the welds connecting the vertical web stiffeners to the top flanges of the main girders. The cracks might possibly be causing serious problems if they are allowed to propagate through the entire length of the weld, thereby permitting out-of-plane bending of the main girder web. In order to identify the reason for the observed cracks, an ongoing investigation under the commision of the bridge owner was started in the spring of 2009. One conclusion so far, is that the observed cracks conclusively are a result of fatigue As a part of a master thesis, FEM-modelling is currently under way. As the fatigue process is distortional, the propagation phase of the observed cracks might slow down or even stop. One task will be to determine the stress intensity factor versus crack length relationship in order to model a growing crack. The final chosen method of refurbishment will be based upon the results of the study and will be implemented in cooperation with the bridge owner.
{"title":"The Instrumentation and monitoring of the Vårby Bridge","authors":"Mattias Nilsson, K. Eriksson, G. James, P. Collin","doi":"10.2749/222137810796024628","DOIUrl":"https://doi.org/10.2749/222137810796024628","url":null,"abstract":"Numerous cracks have been discovered in the Varby Bridge near Stockholm, Sweden. All cracks are found at the junctions between the cross girders and the main girders, more specifically, at the welds connecting the vertical web stiffeners to the top flanges of the main girders. The cracks might possibly be causing serious problems if they are allowed to propagate through the entire length of the weld, thereby permitting out-of-plane bending of the main girder web. In order to identify the reason for the observed cracks, an ongoing investigation under the commision of the bridge owner was started in the spring of 2009. One conclusion so far, is that the observed cracks conclusively are a result of fatigue As a part of a master thesis, FEM-modelling is currently under way. As the fatigue process is distortional, the propagation phase of the observed cracks might slow down or even stop. One task will be to determine the stress intensity factor versus crack length relationship in order to model a growing crack. The final chosen method of refurbishment will be based upon the results of the study and will be implemented in cooperation with the bridge owner.","PeriodicalId":10841,"journal":{"name":"CTIT technical reports series","volume":"67 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2010-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84876395","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-01-01DOI: 10.3929/ETHZ-A-006859451
Yi Wei, M. Oriol, B. Meyer
Most approaches to testing use branch coverage to decide on the quality of a given test suite. The intuition is that covering branches relates directly to uncovering faults. In this article we present an empirical study that applied random testing to 14 Eiffel classes for a total of 2520 hours and recorded the number of uncovered faults and the branch coverage over time. Our results show that: (1) in the tested classes, random testing reaches 93% branch coverage (2) it exercises almost the same set of branches every time, (3) it detects different faults from time to time, (4) during the first 10 minutes of testing while branch coverage increases rapidly, there is a strong correlation between branch coverage and the number of uncovered faults, (5) over 50% of the faults are detected at a time where branch coverage hardly changes and the correlation between branch coverage and the number of uncovered faults is weak. These results provide evidence that branch coverage is not a good stopping criterion for random testing. They also show that branch coverage is not a good indicator for the effectiveness of a test suite.
{"title":"Is coverage a good measure of testing effectiveness?: An assessment using branch coverage and Random testing","authors":"Yi Wei, M. Oriol, B. Meyer","doi":"10.3929/ETHZ-A-006859451","DOIUrl":"https://doi.org/10.3929/ETHZ-A-006859451","url":null,"abstract":"Most approaches to testing use branch coverage to decide on the quality of a given test suite. The intuition is that covering branches relates directly to uncovering faults. In this article we present an empirical study that applied random testing to 14 Eiffel classes for a total of 2520 hours and recorded the number of uncovered faults and the branch coverage over time. Our results show that: (1) in the tested classes, random testing reaches 93% branch coverage (2) it exercises almost the same set of branches every time, (3) it detects different faults from time to time, (4) during the first 10 minutes of testing while branch coverage increases rapidly, there is a strong correlation between branch coverage and the number of uncovered faults, (5) over 50% of the faults are detected at a time where branch coverage hardly changes and the correlation between branch coverage and the number of uncovered faults is weak. These results provide evidence that branch coverage is not a good stopping criterion for random testing. They also show that branch coverage is not a good indicator for the effectiveness of a test suite.","PeriodicalId":10841,"journal":{"name":"CTIT technical reports series","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2010-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86109710","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-01-01DOI: 10.3929/ETHZ-A-006886113
M. Steinová
The design of a scalable overlay network to support decentralized topic-based publish/subscribe communication is nowadays a problem of great importance. We investigate here one such design problem called Minimum Topic-Connected Overlay. Given a collection of users together with the lists of topics they are interested in, connect these users to a network by a minimum number of edges such that every graph induced by users interested in one common topic is connected. It is known that this problem is APX-hard and approximable by a logarithmic factor. We focus here on hardness properties of some special instances. We study the problem where, for each topic, there are at most three users interested in it. Surprisingly, we show that even with such strong restriction, the problem stays NP-hard and it inherits the approximation hardness of the well-known vertex cover problem.
{"title":"On the Approximation of Special Instances of Minimum Topic-Connected Overlay","authors":"M. Steinová","doi":"10.3929/ETHZ-A-006886113","DOIUrl":"https://doi.org/10.3929/ETHZ-A-006886113","url":null,"abstract":"The design of a scalable overlay network to support decentralized topic-based publish/subscribe communication is nowadays a problem of great importance. We investigate here one such design problem called Minimum Topic-Connected Overlay. Given a collection of users together with the lists of topics they are interested in, connect these users to a network by a minimum number of edges such that every graph induced by users interested in one common topic is connected. It is known that this problem is APX-hard and approximable by a logarithmic factor. We focus here on hardness properties of some special instances. We study the problem where, for each topic, there are at most three users interested in it. Surprisingly, we show that even with such strong restriction, the problem stays NP-hard and it inherits the approximation hardness of the well-known vertex cover problem.","PeriodicalId":10841,"journal":{"name":"CTIT technical reports series","volume":"49 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2010-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91154719","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-01-01DOI: 10.3929/ETHZ-A-006857374
Son Hoang
In formal reasoning, modelling and proving activities are closely related. Models give rise to different proof obligations and information about failed proofs gives indications on how models should be improved. This document is an attempt to address the latter issue: to understand how to deal with unprovable obligations. We consider here proof obligations related to invariant preservation of an Event-B model: firstly, to understand the meaning of the proof obligations; secondly, to analyse various ways to fix the model accordingly. Our analysis is based on the concept of reachable states and inductive invariants.
{"title":"How to interpret failed proofs in Event-B","authors":"Son Hoang","doi":"10.3929/ETHZ-A-006857374","DOIUrl":"https://doi.org/10.3929/ETHZ-A-006857374","url":null,"abstract":"In formal reasoning, modelling and proving activities are closely related. Models give rise to different proof obligations and information about failed proofs gives indications on how models should be improved. This document is an attempt to address the latter issue: to understand how to deal with unprovable obligations. We consider here proof obligations related to invariant preservation of an Event-B model: firstly, to understand the meaning of the proof obligations; secondly, to analyse various ways to fix the model accordingly. Our analysis is based on the concept of reachable states and inductive invariants.","PeriodicalId":10841,"journal":{"name":"CTIT technical reports series","volume":"88 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2010-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83420606","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-01-01DOI: 10.3929/ETHZ-A-006906008
Son Hoang, Simon Hudon
Event-B is a formal method that allows one to model various kinds of systems including control systems working within some fragile environment. However, it is lacking a systematic approach for developing this type of systems and it hinders the applicability of Event-B. Our contribution is such an approach and it is presented in this paper. Our proposed method focuses on a set of elements that should be captured by the formal model and prescribes an order in which they should be introduced. The key aspect of our approach is to first model the required behaviour of the environment, and then to introduce the controller to appropriately influence the environment. It has the advantage that every step of the such a development is dictated by the information available so far, including the requirements. We argue that having a clear development strategy early in the design process will assist the developers in producing high-quality models of the future software systems.
{"title":"Developing control systems with some fragile environment","authors":"Son Hoang, Simon Hudon","doi":"10.3929/ETHZ-A-006906008","DOIUrl":"https://doi.org/10.3929/ETHZ-A-006906008","url":null,"abstract":"Event-B is a formal method that allows one to model various kinds of systems including control systems working within some fragile environment. However, it is lacking a systematic approach for developing this type of systems and it hinders the applicability of Event-B. Our contribution is such an approach and it is presented in this paper. Our proposed method focuses on a set of elements that should be captured by the formal model and prescribes an order in which they should be introduced. The key aspect of our approach is to first model the required behaviour of the environment, and then to introduce the controller to appropriately influence the environment. It has the advantage that every step of the such a development is dictated by the information available so far, including the requirements. We argue that having a clear development strategy early in the design process will assist the developers in producing high-quality models of the future software systems.","PeriodicalId":10841,"journal":{"name":"CTIT technical reports series","volume":"49 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2010-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79316405","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper analyses worker transitions on the German labour market derived from different data sources. These include the two German micro data sets which provide high-frequency observations on workers' employment and unemployment histories: the German Socioeconomic Panel (SOEP) and the IAB Employment Subsample (IABS). This exercise thus yields a comprehensive overview of German labour market dynamics. Furthermore, it highlights the differences between the results obtained from a retrospective survey, the SOEP, and a process-induced administrative data set, the IABS. In particular, our analysis shows which groups of the labour market are particularly affected by measurement error. We also show which role measurement issues play when establishing the stylised facts about the cyclicality of labour market dynamics.
{"title":"Biases in the measurement of labour market dynamics","authors":"Ronald Bachmann, S. Schaffner","doi":"10.17877/DE290R-3021","DOIUrl":"https://doi.org/10.17877/DE290R-3021","url":null,"abstract":"This paper analyses worker transitions on the German labour market derived from different data sources. These include the two German micro data sets which provide high-frequency observations on workers' employment and unemployment histories: the German Socioeconomic Panel (SOEP) and the IAB Employment Subsample (IABS). This exercise thus yields a comprehensive overview of German labour market dynamics. Furthermore, it highlights the differences between the results obtained from a retrospective survey, the SOEP, and a process-induced administrative data set, the IABS. In particular, our analysis shows which groups of the labour market are particularly affected by measurement error. We also show which role measurement issues play when establishing the stylised facts about the cyclicality of labour market dynamics.","PeriodicalId":10841,"journal":{"name":"CTIT technical reports series","volume":"46 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2009-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87365983","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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