UML Class Diagram or Entity Relationship Diagram : An Object Relational Impedance Mismatch

It is now nearly 30 years since Peter Chen’s watershed paper “The Entity-Relationship Model –towards a Unified View of Data”. [1] The entity relationship model and variations and extensions to ithave been taught in colleges and universities for many years. In his original paper Peter Chen looked at converting his new ER model to the then existing data structure diagrams for the Network model. In recent years there has been a tendency to use a Unified Modelling Language (UML) class diagram forconceptual modeling for relational databases, and several popular course text books use UMLnotation to some degree [2] [3]. However Object and Relational technology are based on different paradigms. In the paper we argue that the UML class diagram is more of a logical model (implementation specific). ER Diagrams on theother hand, are at a conceptual level of database design dealing with the main items and their relationships and not with implementation specific detail. UML focuses on OOAD (Object Oriented Analysis and Design) and is navigational and program dependent whereas the relational model is set based and exhibits data independence. The ER model provides a well-established set of mapping rules for mapping to a relational model. In this paper we look specifically at the areas which can cause problems for the novice databasedesigner due to this conceptual mismatch of two different paradigms. Firstly, transferring the mapping of a weak entity from an Entity Relationship model to UML and secondly the representation of structural constraints between objects. We look at the mixture of notations which students mistakenly use when modeling. This is often the result of different notations being used on different courses throughout their degree. Several of the popular text books at the moment use either a variation of ER,UML, or both for teaching database modeling. At the moment if a student picks up a text book they could be faced with either; one of the many ER variations, UML, UML and a variation of ER both covered separately, or UML and ER merged together. We regard this problem as a conceptual impedance mismatch. This problem is documented in [21] who have produced a catalogue of impedance mismatch problems between object-relational and relational paradigms. We regard the problems of using UML class diagrams for relational database design as a conceptual impedance mismatch as the Entity Relationship model does not have the structures in the model to deal with Object Oriented concepts Keywords: EERD, UML Class Diagram, Relational Database Design, Structural Constraints, relational and object database impedance mismatch. The ER model was originally put forward by Chen [1] and subsequently extensions have been added to add further semantics to the original model; mainly the concepts of specialisation, generalisation and aggregation. In this paper we refer to an Entity-Relationship model (ER) as the basic model and an extended or enhanced entity-relationship model (EER) as a model which includes the extra concepts. The ER and EER models are also often used to aid communication between the designer and the user at the requirements analysis stage. In this paper when we use the term “conceptual model” we mean a model that is not implementation specific.ISBN: 978-84-616-3847-5 3594Peer reviewe

Capital and Punishment: Resource Scarcity Increases Endorsement of the Death Penalty

Faced with punishing severe offenders, why do some prefer imprisonment whereas others impose death? Previous research exploring death penalty attitudes has primarily focused on individual and cultural factors. Adopting a functional perspective, we propose that environmental features may also shape our punishment strategies. Individuals are attuned to the availability of resources within their environments. Due to heightened concerns with the costliness of repeated offending, we hypothesize that individuals tend toward elimination-focused punishments during times of perceived scarcity. Using global and United States data sets (studies 1 and 2), we find that indicators of resource scarcity predict the presence of capital punishment. In two experiments (studies 3 and 4), we find that activating concerns about scarcity causes people to increase their endorsement for capital punishment, and this effect is statistically mediated by a reduced willingness to risk repeated offenses. Perceived resource scarcity shapes our punishment preferences, with important policy implications

The disposition effect among mutual fund participants : a re- examination

Using information on mutual fund trades executed from 1998 to 2017 by 31,513 individual investor clients of a major Portuguese financial institution, we study the relationship between the disposition effect, financial literacy and trading experience. We find that mutual fund investors exhibit strong disposition effect. The tendency to hold losers is partially offset with literacy: not only holding a university degree reduces the propensity to hold on to loser funds but also higher financial knowledge and stronger math skills reduce the disposition effect. Literacy also plays a role in shaping the way experience affects this bias. Evidence of the disposition effect persists after accounting for redemption fees, bad emotions, irrational beliefs, market sentiment and the existence of someone to blame.info:eu-repo/semantics/publishedVersio

Metamodeling in EIA/CDIF - Meta-Metamodel and Metamodels

This article introduces the EIA/CDIF set of standards for the modeling of information systems and its exchange among computer-aided software tools of different vendors. It lays out the meta-metamodel and the standardized metamodels which are fully depicted in a hierarchical layout and annotated with the unique identifiers of all the standardized modeling concepts. The article also stresses the fact that EIA/CDIF has been used as the baseline in the creation of an international standard, the ISO/CDIF set of models, an ongoing project

Postponement and childlessness: Evidence from two British Cohorts

This paper starts by reviewing existing projections of childlessness among British men and women. Low current fertility implies high eventual childlessness unless the postponement of parenthood is taken into account. Such re-timing of first births appears to be occurring differentially across social groups. Exploiting the disaggregated evidence of two British cohort studies, the 1958 National Child Development Study and the 1970 British Cohort Survey, this paper investigates the extent of postponement across cohorts and projects its impact on eventual levels of childlessness. Men and women are considered separately in our models of a population stratified by educational attainment. We find the most striking postponement occurring among graduate men. Among graduate women, after taking family building intentions into account, we estimate that about a quarter of 1970 born graduate women will remain childless, rather than something nearer 40 per cent as had been conjectured elsewhere

Who Starts with Open Source? Institutional Choice of Start-Ups in the German ICT Sector

We analyze the characteristics of new businesses in the German ICT industry, distinguishing them based on their choice between two IPR regimes: open source software (OSS) or closed source software (CSS). The share of new firms with an OSS-based business model has increased considerably over the last several years. OSS-based firms tend to be smaller (in terms of staff and capital) and experience less shortages of capital. Only older cohorts of OSS-intensive start-ups had more difficulty than their CSS counterparts in convincing potential financiers of their viability, indicating that OSS business models are now well established. We find no evidence that the lower entry barriers for OSS firms are particularly attractive to start-ups with low human capital endowment or to necessity-motivated entrepreneurs.New business formation, institutions, open source, intellectual property rights, software industry

Does Qualification Drive Innovation? A Microeconometric Analysis Using Linked-employer-employee Data

Degree-level science and engineering skills as well as management and leadership skills are often referred to as a source of innovative activities within companies. Broken down by sectoral innovation patterns, this article examines the role of formal education and actual occupation for product innovation performance in manufacturing firms within a probit model. It uses unique micro data for Germany (LIAB) that contain detailed information about innovative activities and the qualification of employees. We find significant differences of the human capital endowment between sectors differentiated according to the Pavitt classification. Sectors with a high share of highly skilled employees engage in product innovation above average (specialized suppliers and science based industries). According to our hitherto estimation results, within these sectors the share of highly skilled employees does not, however, substantially increase the probability to be an innovative firm.innovation, human capital, qualification, sectoral innovation system