When defining a domain-specific modeling language (DSML), the two key components that have to be specified are its syntax and semantics. For specifying a modeling languages' abstract syntax, metamodels are the standard means. MOF provides a standardized, well established, and widely accepted metamodeling language enabling the definition of metamodels and the generation of accompanying modeling facilities. However, no such standard means exist for specifying the behavioral semantics of a DSML. This hampers the efficient development of model execution facilities, such as debugging, simulation, and verification. To overcome this limitation, we propose to integrate fUML with MOF to enable the specification of the behavioral semantics for DSMLs in terms of fUML activities. We discuss alternatives how this integration can be achieved and show by-example how to specify the semantics of a DSML using fUML. To reuse existing runtime infrastructures, we further demonstrate the usage of external libraries in fUML-based specifications.
In model-driven engineering, models are primary artifacts that can evolve heavily during their life cycle. Therefore, versioning of models is a key technique to be offered by integrated development environments for model-driven engineering. In contrast to text-based versioning systems, we present an approach that takes model structures and their changes over time into account. Considering model structures as graphs, we define a fundamental approach where model revisions are considered as graph modifications consisting of delete and insert actions. Two different kinds of conflict detection are presented: (1) the check for operation-based conflicts between different graph modifications, and (2) the check for state-based conflicts on merged graph modifications. For the merging of graph modifications, a two-phase approach is proposed: First, operational conflicts are temporarily resolved by always giving insertion priority over deletion to keep as much information as possible. Thereafter, this tentative merge result is the basis for manual conflict resolution as well as for the application of repair actions
This study investigated the changing achievement relationships among students based on ages at entry into first grade and ages relative to their classmates. Data from students in grades 4, 8, and 11 were selected from National Assessment of Educational Progress achievement data in mathematics, science, and reading collected from national samples of year-old students. Relative age, class age, sex, parental education, home environment, and type of community were entered in stepwise multiple regression analyses. The achievement data for Caucasians indicated that the significantly higher achievement of the oldest as compared to the youngest students at age 9 remained significant, but decreased at age 13, and disappeared by age 17. For blacks, while the trend did not decrease at age 13, it also disappeared at age 17. A second analysis of the proportion of students retained one grade revealed significantly increasing proportions of retained students as relative age became younger for Caucasians and blacks. Clinical screening based on sex and school district entrance age requirements was suggested for several groups. Signs of inadequate readiness in some of these groups pose potentially serious threats to academic careers and suggest delaying entrance for a year. Is there a best age for all children to enter the first grade? This difficult question has long concerned parents, educators, administrators, and legis-This article is based on a paper given at Downloaded from LANGER, KALK, AND SEARLS lators (Hedges, 1977). The common criterion used by school districts for entrance into the first grade has been chronological age, with admission usually allowed only at the beginning of the school year (Jones, 1968). Such a simple criterion has obvious administrative advantages but also encourages pressure for change from parents and teachers. The result is frequent legislative reexamination of the laws governing entrance age (Carline, 1964; Educational Research Service [ERS], 1975). The confusion and ambiguity about these policies can be seen in the range of 5 calendar months among the entrance age requirements for the nation's school districts (ERS, 1975; National Institute of Education, 1978). But school budget constraints and inadequate research have left the simple age requirement as the normal admission policy to first grade. Comparisons of the academic achievement of children entering school at the opposite ends of the normal 12-month entrance age period have demonstrated that the younger students receive lower school grades and score lower on achievement tests. These findings have been consistent, starting with Bigelow (1934), through King (1955), Green and Simmons (1962), Carrol (1963), and Hall (1963).Most of the research has dealt with both restricted populations and grade ranges. However, in a study covering a more extended grade range, Miller and Norris (1967) found the initial academic differences attenuating between normally entering older and younger children as they progressed through elementary school.The Colema...
Highlights► Detection of applications of composite operations in evolving software models. ► Automatic generation of detection rules from executable operation specifications. ► Real-world study showing that 70% of all applied composite operations can be detected. ► Performance analysis showing that detection algorithm scales well for large models.
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