The Advice Complexity of a Class of Hard Online Problems

The advice complexity of an online problem is a measure of how much knowledge of the future an online algorithm needs in order to achieve a certain competitive ratio. Using advice complexity, we define the first online complexity class, AOC. The class includes independent set, vertex cover, dominating set, and several others as complete problems. AOC-complete problems are hard, since a single wrong answer by the online algorithm can have devastating consequences. For each of these problems, we show that $\log\left(1+(c-1)^{c-1}/c^{c}\right)n=\Theta (n/c)$ bits of advice are necessary and sufficient (up to an additive term of $O(\log n)$) to achieve a competitive ratio of $c$. The results are obtained by introducing a new string guessing problem related to those of Emek et al. (TCS 2011) and B\"ockenhauer et al. (TCS 2014). It turns out that this gives a powerful but easy-to-use method for providing both upper and lower bounds on the advice complexity of an entire class of online problems, the AOC-complete problems. Previous results of Halld\'orsson et al. (TCS 2002) on online independent set, in a related model, imply that the advice complexity of the problem is $\Theta (n/c)$. Our results improve on this by providing an exact formula for the higher-order term. For online disjoint path allocation, B\"ockenhauer et al. (ISAAC 2009) gave a lower bound of $\Omega (n/c)$ and an upper bound of $O((n\log c)/c)$ on the advice complexity. We improve on the upper bound by a factor of $\log c$. For the remaining problems, no bounds on their advice complexity were previously known.Comment: Full paper to appear in Theory of Computing Systems. A preliminary version appeared in STACS 201

Fragmenterne skal samles

Kommentar til artiklen “MONA i Middelfart – konference om flere og bedre naturfagslærere”, MONA2010‑1

ANACONDA: a new tool to improve mortality and cause of death data

The need to monitor the Sustainable Development Goals (SDGs) and to have access to reliable and timely mortality data has created a strong demand in countries for tools that can assist them in this. ANACONDA (Analysis of National Causes of Death for Action) is a new tool developed for this purpose which allows countries to assess how accurate their mortality and cause of death are. Applying ANACONDA will increase confidence and capacity among data custodians in countries about their mortality data and will give them insight into quality problems that will assist the improvement process.; ANACONDA builds on established epidemiological and demographic concepts to operationalise a series of 10 steps and numerous sub-steps to perform data checks. Extensive use is made of comparators to assess the plausibility of national mortality and cause of death statistics. The tool calculates a composite Vital Statistics Performance Index for Quality (VSPI(Q)) to measure how fit for purpose the data are. Extracts from analyses of country data are presented to show the types of outputs.; Each of the 10 steps provides insight into how well the current data is describing different aspects of the mortality situation in the country, e.g. who dies of what, the completeness of the reporting, and the amount and types of unusable cause of death codes. It further identifies the exact codes that should not be used by the certifying physicians and their frequency, which makes it possible to institute a focused correction procedure. Finally, the VSPI(Q) allows periodic monitoring of data quality improvements and identifies priorities for action to strengthen the Civil Registration and Vital Statistics (CRVS) system.; ANACONDA has demonstrated the potential to dramatically improve knowledge about disease patterns as well as the functioning of CRVS systems and has served as a platform for galvanising wider CRVS reforms in countries

Naturfagene i den nye læreruddannelse?

Artiklen præsenterer en gennemgang af naturfagenes situation på læreruddannelsesinstitutionerneigennem de seneste 20 år med henblik på at dokumentere et kritisk fald af studerende inaturfagene i samme tidsrum. Anledningen er at der i indeværende studieår indføres en ny læreruddannelse.Artiklen beskriver det forberedende arbejde som topstyret og forceret. Under de givne rammersamarbejdede de fire naturfaglige skrivegrupper om målformuleringer som vil øge mulighederne fortværfaglighed og etablering af en naturfaglig profil for de lærerstuderende. Forfatterne sætter imidlertidspørgsmålstegn ved om en ny organisering og evalueringsprocedure vil ændre væsentligt vednaturfagenes problematiske situation i læreruddannelsen.

Labour mobility in Australia : a study of differentials in movement between localities, occupations and jobs

Labour mobility has been a subject of inquiry mainly within the discipline of economics, which naturally has given more emphasis to economic determinants than to social and demographic characteristics. In recent years one approach, the dual labour market theory, has aroused considerable interest among scholars and policy makers overseas and is claimed to provide valuable new insight into economic, institutional and sociological factors which impede the efficient operation of the labour market. This thesis is an investigation of labour mobility in Australia focussing in particular on differentials between occupations and other labour market groups. By examining several main types of mobility the study attempts to give a more complete view of labour dynamics than has been done hitherto in Australia. Although an interdisciplinary approach has been adopted the orientation and methodology used are demographic with a subsequent concentration on those aspects of labour mobility which are of greatest concern to demographers. Apart from this orientation the thesis aims at being comprehensive rather than detailing any particular mobility aspects, and generalizations are sought which are applicable to the country as a whole. Thus, from the large array of statistics which have been brought together and analyzed in this study the aim has been to provide an overview of labour mobility in Australia between 1966 and 1976. A conceptual framework developed in the beginning of the thesis helps to integrate the various mobility aspects and provides a base for interpreting the empirical findings. The major inputs to the framework were derived from the above mentioned theory of labour market segmentation, from vocational development theory and from the demographic approaches to the life cycle. A main advantage of this multidisciplinary approach is the recognition that both demand and supply factors determine mobility and that both contribute to the subdivision of the labour market into distinctive groups with different mobility behaviour. The thesis shows that in spite of a substantial labour force expansion in the period under investigation, occupational growth rates varied considerably. Underlying the net changes were large flows of workers into and out of the labour force, overseas migration, changes in work force participation and the movement of labour between occupations and industries. Many workers also moved spatially in Australia between 1966-71, particularly within and between the capital cities. This is illustrated by the fact that 44 per cent of all workers made a residential shift and, despite the large distances, one move in four was to another State. Of greater concern, though, to this study was the finding that the likelihood of workers migrating was related to their occupation and more broadly to the labour market segment to which they belonged. A particular question examined was whether relatively homogeneous groups of occupations could be identified on the basis of similar patterns of worker movement. Although, little support could be found for this proposition, it was, nonetheless, possible to determine a number of general attributes of work and career which led to mobility or immobility in the various occupations. In common with spatial mobility, occupational differences in the movement of workers between jobs and occupations were pronounced and largely confirmed framework expectations. In particular, the evidence showed that primary and secondary workers differ in their spatial, job and occupational mobilities, that most moves occur while workers are in the early stages of working life, that a small groups of frequent job changers contributed excessively to the overall job mobility and that the periodic moves of intermittent workers into and out of the labour force substantially influenced turnover levels. On the other hand, the differences found in the mobility behaviour of male and female workers were not always as large as expected. This may have resulted, however, from the severe restrictions on data disaggregation, a problem which seriously inhibited the depth of many analyses. From the insight provided by the framework it would appear that the segmented approach to the labour market, and the view that mobility is conditioned by many personal factors which vary over life, is appropriate for understanding much labour mobility in Australia

Efteruddannelse af naturfaglærere

Inddragelse af uformelle læringsmiljøer i form af virksomhedsbesøg og ekskursioner i lokalmiljøet på Lolland-Falster og Møn udgjorde en af grundstenene i efteruddannelseskonceptet i NOFANprojektet (Naturfaglig Opkvalificering via Faglig undervisning, Aktivitetscentre og lokal Netværksdannelse), hvor det blev sammenkoblet med linjefagsundervisning inden for naturfaglige kerneområder og fagdidaktiske overvejelser. Ud fra kursisternes indholdsplaner og undervisernes evalueringer kan vi konkludere at et undervisningsforløb hvor studerende får friere hænder og mulighed for at få ny inspiration gennem virksomhedstilknytning, er med til at stimulere læringen. Engagement, høj faglighed og selvstændighed samt eksperimenterende aktiviteter og forløb har kendetegnet kursisternes arbejde