Relational Foundations For Functorial Data Migration

We study the data transformation capabilities associated with schemas that are presented by directed multi-graphs and path equations. Unlike most approaches which treat graph-based schemas as abbreviations for relational schemas, we treat graph-based schemas as categories. A schema $S$ is a finitely-presented category, and the collection of all $S$-instances forms a category, $S$-inst. A functor $F$ between schemas $S$ and $T$, which can be generated from a visual mapping between graphs, induces three adjoint data migration functors, $\Sigma_F:S$-inst$\to T$-inst, $\Pi_F: S$-inst $\to T$-inst, and $\Delta_F:T$-inst $\to S$-inst. We present an algebraic query language FQL based on these functors, prove that FQL is closed under composition, prove that FQL can be implemented with the select-project-product-union relational algebra (SPCU) extended with a key-generation operation, and prove that SPCU can be implemented with FQL

Monitoring international migration flows in Europe. Towards a statistical data base combining data from different sources

The paper reviews techniques developed in demography, geography and statistics that are useful for bridging the gap between available data on international migration flows and the information required for policy making and research. The basic idea of the paper is as follows: to establish a coherent and consistent data base that contains sufficiently detailed, up-to-date and accurate information, data from several sources should be combined. That raises issues of definition and measurement, and of how to combine data from different origins properly. The issues may be tackled more easily if the statistics that are being compiled are viewed as different outcomes or manifestations of underlying stochastic processes governing migration. The link between the processes and their outcomes is described by models, the parameters of which must be estimated from the available data. That may be done within the context of socio-demographic accounting. The paper discusses the experience of the U.S. Bureau of the Census in combining migration data from several sources. It also summarizes the many efforts in Europe to establish a coherent and consistent data base on international migration. The paper was written at IIASA. It is part of the Migration Estimation Study, which is a collaborative IIASA-University of Groningen project, funded by the Netherlands Organization for Scientific Research (NWO). The project aims at developing techniques to obtain improved estimates of international migration flows by country of origin and country of destination

Internal Migration and Regional Population Dynamics in Europe: Romanian Case Study

The report analyses population migration and change in Romania over the period 1984-1994. The analysis of population change is conducted for 2948 communes and towns, the finest administrative division for which population data are available. The lack of migration data on the level of communes and towns makes in-depth analysis of the migration for small spatial units impossible. For that reason analysis of the patterns of migration is conducted for 40 Judete (also referred to as counties or regions) and the capital city of Bucharest, i.e. 41 units altogether. Council of Europe Publishing, F-67075 Strasbourg - Cedex, France

Fuel Costs, Migration, and Community Viability

ISER researchers compiled and reviewed existing studies and data sources relating to the economic and social viability of remote rural Alaska communities. We particularly looked for possible linkages between high fuel costs and migration. Our review indicates the following: (1) migration from smaller places toward larger places is an ongoing phenomenon that is more noticeable when birth rates drop; (2) there is no systematic empirical evidence that fuel prices, by themselves, have been a definitive cause of migration; (3) the pursuit of economic and educational opportunities appears to be a predominant cause of migration; (4) however, currently available survey data are not sufficient to definitively determine other reasons for migration, which could include concerns about public safety and/or alcohol abuse; 5) most of the survey data pre-date the latest rapid increase (2006-2008) in fuel prices. We suggest several ways that better data could be collected on community viability and the reasons for migration.First Alaskans Institute. Alaska Native Policy Center.Introduction / Methods / Findings / Significant data collection opportunities / Conclusions / References / Data Sources Use

No. 23: Labour Migration Trends and Policies in Southern Africa

Since 1990, there have been major changes to longstanding patterns of intra-regional labour migration within the Southern African Development Community (SADC). At the same time, new channels of migration to and from the region have opened. Labour migration is now more voluminous, dynamic and complex than it has ever been. This presents policy-makers with considerable opportunities and challenges. In order to understand the exact nature of these challenges, it is important to have a good grasp of current labour migration characteristics and trends. Unfortunately, reliable, accurate and comprehensive data on labour migration is not available. The quality and currency of data varies considerably from country to country. A regional labour migration observatory would make the future writing of an overview of migration trends a much easier task. The primary objectives of this overview of labour migration trends and policy implications is fourfold: (a) to review recent characteristics and trends in labour migration within and from the SADC region. Official statistics as well as recent survey data are drawn on to generate an overall picture of current characteristics and trends in the region; (b) to highlight some of the critical and urgent issues pertaining to labour migration in the region; (c) to discuss the main features of labour migration strategies and policies and legislative and regulatory frameworks in countries covered by the Southern African Development Community (SADC); and (d) to review the prospects for the freer circulation of migrant labour in the Southern African region. This brief focuses primarily on the period since 1990 and restructuring of labour migration in the wake of the collapse of apartheid, new global migration forces, the end of the wars in Mozambique and Angola and the current economic and political situation in Zimbabwe. Although the brief provides an overview of the region as a whole, the report concentrates on the major labour migration channels in the region (from countries such as Lesotho, Swaziland, Malawi, Mozambique and Zimbabwe to South Africa). The report also considers the nature and implications of new migrant movements to and from SADC

An Age-Period-Cohort Database of Inter-Regional Migration in Australia and Britain, 1976-96

Report prepared as part of a collaborative project on "Migration Trends in Australia and Britain: Levels and Trends in an Age-Period-Cohort Framework" funded by the Economic and Social Research Council and the Australian Research Council. This paper describes the way in which parallel databases of inter-regional migration flows for Australia and Britain, classified by five year ages and birth cohorts for four five year periods between 1976 and 1996. The data processing involves estimation of migration data for comparable spatial units, the reduction of the number of those units to a reduced set for ease of analysis, the extraction of migration data from official data files supplied by the Australian Bureau of Statistics and the Office for National Statistics, and the filling of gaps in these files through iterative proportional fitting for some of the British data. The final stage in preparation of the migration databases was to estimate the numbers of transitions (Australia) or movements (Britain) for age-period-cohort spaces. In principle, this last estimation involves a fairly simple interpolation or aggregation of age-time classified migration data, but in practice a great deal of detailed attention is required. A final section specifies the populations at risk to be used for each age-period-cohort observation plan to compute migration intensities

A Kosloff/Basal method, 3D migration program implemented on the CYBER 205 supercomputer

Conventional finite difference migration has relied on approximations to the acoustic wave equation which allow energy to propagate only downwards. Although generally reliable, such approaches usually do not yield an accurate migration for geological structures with strong lateral velocity variations or with steeply dipping reflectors. An earlier study by D. Kosloff and E. Baysal (Migration with the Full Acoustic Wave Equation) examined an alternative approach based on the full acoustic wave equation. The 2D, Fourier type algorithm which was developed was tested by Kosloff and Baysal against synthetic data and against physical model data. The results indicated that such a scheme gives accurate migration for complicated structures. This paper describes the development and testing of a vectorized, 3D migration program for the CYBER 205 using the Kosloff/Baysal method. The program can accept as many as 65,536 zero offset (stacked) traces