Empirically evaluating OCL and Java for specifying constraints on UML models

The Object Constraint Language (OCL) has been applied, along with UML models, for various purposes such as supporting model-based testing, code generation, and automated consistency checking of UML models. However, a lot of challenges have been raised in the literature regarding its applicability in industry such as extensive training, slow learning curve, and significant effort to use OCL due to lack of familiarity of practitioners. To confirm these challenges, empirical evidence is needed, which is severely lacking in the literature. To build such preliminary evidence, we report a controlled experiment that was designed to evaluate OCL by comparing it with Java; a programming language that has also been used to specify constraints on UML models. Results show that the participants using OCL perform as good as the participants working with Java in terms of three objective quality metrics (i.e., completeness, conformance and redundancy) and two subjective metrics (i.e., applicability and confidence level). In addition, the participants using OCL performed consistently well for all the constraints of varying complexity, while fluctuating results were obtained for the participants using Java for the same constraints. Based on the empirical evidence, we can conclude that it does not make much difference to use OCL or Java for specifying constraints on UML models. However, the participants working with OCL performed consistently well on specifying constraints of varying complexity suggesting that OCL can be used to model complicated constraints (commonly observed in industrial applications) with the same quality as for simpler constraints. Moreover, additional analyses on the constraints when using Java and OCL tools revealed that tools are needed to specify fully correct constraints that can be used to support automation.     

Test data generation for web application using a UML class diagram with OCL constraints

In this paper, we report on our current work toward efficient and effective verification of web application’s basic design. We use a UML class diagram with Object Constraint Language (OCL) to describe the application behaviors and data constraints. Then we generate test data from the formally represented specifications. We make the observation that key web application behaviors can be captured through table size constraints as well as data constraints like foreign key constraints. Based on the observation, we translate the OCL specification into the equivalent constraints using table size expressions. We present a scheme to generate test data from the translated constraints using a Satisfiability Modulo Theories solver. We employ two techniques to reduce constraints. The first is string handling and the other is decomposition of table structures. We also report on an experimental result of test data generation. The result indicates a potential that our scheme works well for real applications in reasonable times.     

OCL约束验证与实现的方法

为了能在运行时验证OCL约束,提出了约束验证框架.针对OCL-Java代码(即OCL约束对应的可执行Java代码)插入的简单方案和封装方法存在的不足,给出了改进的代码插入方案,其中应用异常处理技术从而能够捕获冲突的约束.为了使OCL-Java代码根据设计的代码模式插入到Java程序中,对Java解析器作了修改.最后,实验结果表明了该方法的可行性.     

Modeling and validating Mondex scenarios described in UML and OCL with USE

This paper describes the Mondex case study with UML class diagrams and restricting OCL constraints. The constraints have been formulated either as OCL class invariants or as OCL pre- and postconditions. The proposed two models include UML class diagrams and OCL constraints which have been checked by the UML and OCL tool USE (UML-based Specification Environment). USE allows validation of a model by testing it with scenarios. The Mondex case study has been validated by positive and negative test cases. The test cases allow the validity of the various constraints to be traced and checked. Validation results are presented as textual protocols or as UML sequence diagrams where starting, intermediate, and resulting system states are represented by UML object diagrams. UML sequence diagrams, UML object diagrams, and textual protocols are shown with varying degrees of detail for the attributes, constraints, and executed commands. J. C. P. Woodcock     

Towards evolvable Internet architecture-design constraints and models analysis

There is a general consensus about the success of Internet architecture in academia and industry. However, with the development of diversified application, the existing Internet architecture is facing more and more challenges in scalability, security, mobility and performance. A novel evolvable Internet architecture framework is proposed in this paper to meet the continuous changing application requirements. The basic idea of evolvability is relaxing the constraints that limit the development of the architecture while adhering to the core design principles of the Internet. Three important design constraints used to ensure the construction of the evolvable architecture, including the evolvability constraint, the economic adaptability constraint and the manageability constraint, are comprehensively described. We consider that the evolvable architecture can be developed from the network layer under these design constraints. What＇s more, we believe that the address system is the foundation of the Internet. Therefore, we propose a general address platform which provides a more open and efficient network environment for the research and development of the evolvable architecture.     

OCL for formal modelling of topological constraints involving regions with broad boundaries

Integrity constraints can control topological relations of objects in spatial databases. These constraints can be modelled using formal languages such as the spatial extension of the Object Constraint Language (Spatial OCL). This language allows the expression of topological integrity constraints involving crisp spatial objects but it does not support constraints involving spatial objects with vague shapes (e.g. forest stand, pollution zone, valley or lake). In this paper, we propose an extension of Spatial OCL based on (1) a geometric model for objects with vague shapes, and (2) an adverbial approach for modelling topological constraints involving regions with broad boundaries. This new language provides an easiness in the formal modelling of these complex constraints. Our approach has been implemented in a code generator. A case study is also presented in the paper in the field of agriculture spreading activities. AOCL _OVS takes account of the shape vagueness of spread parcel and improve spatial reasoning about them.     

Stress constraints sensitivity analysis in structural topology optimization

Sensitivity Analysis is an essential issue in the structural optimization field. The calculation of the derivatives of the most relevant quantities (displacements, stresses, strains) in optimum design of structures allows to estimate the structural response when changes in the design variables are introduced. This essential information is used by the most frequent conventional optimization algorithms (SLP, MMA, Feasible directions) in order to reach the optimal solution. According to this idea, the Sensitivity Analysis of the stress constraints in Topology Optimization problems is a crucial aspect to obtain the optimal solution when stress constraints are considered.Maximum stiffness approaches usually involve one linear constraint and one non-linear objective function. Thus, the computation of the required sensitivity analysis does not mean a crucial limitation. However, in the topology optimization problem with stress constraints, efficient and accurate computation of the derivatives is needed in order to reach appropriate optimal solutions. In this paper, a complete analytic and efficient procedure to obtain the Sensitivity Analysis of the stress constraints in topology optimization of continuum structures is analyzed. First order derivatives and second order directional derivatives of the stress constraints are analyzed and included in the optimization procedure. In addition, topology optimization problems usually involve thousands of design variables and constraints. Thus, an efficient implementation of the algorithms used in the computation of the Sensitivity Analysis is developed in order to reduce the computational cost required. Finally, the sensitivity analysis techniques presented in this paper are tested by solving some application examples.     

Relaxing constraints in enhanced entity-relationship models using fuzzy quantifiers

While various articles about fuzzy entity relationship (ER) and enhanced entity relationship (EER) models have recently been published, not all examine how the constraints expressed in the model may be relaxed. In this paper, our aim is to relax the constraints which can be expressed in a conceptual model using the modeling tool, so that these constraints can be made more flexible. We will also study new constraints that are not considered in classic EER models. We use the fuzzy quantifiers which have been widely studied in the context of fuzzy sets and fuzzy query systems for databases. In addition, we shall examine the representation of these constraints in an EER model and their practical repercussions. The following constraints are studied: the fuzzy participation constraint, the fuzzy cardinality constraint, the fuzzy completeness constraint to represent classes and subclasses, the fuzzy cardinality constraint on overlapping specializations, fuzzy disjoint and fuzzy overlapping constraints on specializations, fuzzy attribute-defined specializations, fuzzy constraints in union types or categories and fuzzy constraints in shared subclasses. We shall also demonstrate how fuzzy (min, max) notation can substitute the fuzzy cardinality constraint but not the fuzzy participation constraint. All these fuzzy constraints have a new meaning, they offer greater expressiveness in conceptual design, and are included in the so-called fuzzy EER model.     

Validating UML and OCL models in USE by automatic snapshot generation

We study the testing and certification of UML and OCL models as supported by the validation tool USE. We extend the available USE features by introducing a language for defining properties of desired snapshots and by showing how such snapshots are generated. Within the approach, it is possible to treat test cases and validation cases. Test cases show that snapshots having desired properties can be constructed. Validation cases show that given properties are consequences of the original UML and OCL model.     

Surface reconstruction using deformable models with interior andboundary constraints

The authors introduce a technique for 3D surface reconstruction using elastic deformable-models. The model used is an imaginary elastic grid, which is made of membranous, thin-plate-type material. The elastic grid can bent, twisted, compressed, and stretched into any desired 3D shape, which is specified by the shape constraints derived automatically from images of a real 3D object. Shape reconstruction is guided by a set of imaginary springs that enforce the consistency in the position, orientation, and/or curvature measurements of the elastic grid and the desired shape. The dynamics of a surface reconstruction process is regulated by Hamilton's principle or the principle of the least action. Furthermore, a 1D deformable template that borders the elastic grid may be used. This companion boundary template is attracted/repelled by image forces to conform with the silhouette of the imaged object. Implementation results using simple analytic shapes and images of real objects are presented     

Construction and analysis of ground models and their refinements as a foundation for validating computer-based systems

We explain why for the verified software challenge proposed in Hoare (J ACM 50(1): 63–69, 2003), Hoare and Misra (Verified software: theories, tools, experiments. Vision of a Grand Challenge project. In: [Meyer05]) to gain practical impact, one needs to include rigorous definitions and analysis, prior to code development and comprising both experimental validation and mathematical verification, of ground models, i.e., blueprints that describe the required application-content of programs. This implies the need to link via successive refinements the relevant properties of such high-level models in a traceable and checkable way to code a compiler can verify. We outline the Abstract State Machines (ASM) method, a discipline for reliable system development which allows one to bridge the gap between informal requirements and executable code by combining application-centric experimentally validatable system modelling with mathematically verifiable stepwise detailing of abstract models to compile-time-verifiable code.     

Specifying comfortable driving postures for ergonomic design and evaluation of the driver workspace using digital human models

Specifying comfortable driving postures is essential for ergonomic design and evaluation of a driver workspace. The present study sought to enhance and expand upon several existing recommendations for such postures. Participants (n = 38) were involved in six driving sessions that differed by vehicle class (sedan and SUV), driving venue (laboratory-based and field) or seat (from vehicles ranked high and low by vehicle comfort). Sixteen joint angles were measured in preferred postures to more completely describe driving postures, as were corresponding perceptual responses. Driving postures were found to be bilaterally asymmetric and distinct between vehicle classes, venues, age groups and gender. A subset of preferred postural ranges was identified using a filtering mechanism that ensured desired levels of perceptual responses. Accurate ranges of joint angles for comfortable driving postures, and careful consideration of vehicle and driver factors, will facilitate ergonomic design and evaluation of a driver workspace, particularly when embedded in digital human models.     

Extending OCL for OLAP querying on conceptual multidimensional models of data warehouses

The development of data warehouses begins with the definition of multidimensional models at the conceptual level in order to structure data, which will facilitate decision makers with an easier data analysis. Current proposals for conceptual multidimensional modelling focus on the design of static data warehouse structures, but few approaches model the queries which the data warehouse should support by means of OLAP (on-line analytical processing) tools. OLAP queries are, therefore, only defined once the rest of the data warehouse has been implemented, which prevents designers from verifying from the very beginning of the development whether the decision maker will be able to obtain the required information from the data warehouse. This article presents a solution to this drawback consisting of an extension to the object constraint language (OCL), which has been developed to include a set of predefined OLAP operators. These operators can be used to define platform-independent OLAP queries as a part of the specification of the data warehouse conceptual multidimensional model. Furthermore, OLAP tools require the implementation of queries to assure performance optimisations based on pre-aggregation. It is interesting to note that the OLAP queries defined by our approach can be automatically implemented in the rest of the data warehouse, in a coherent and integrated manner. This implementation is supported by a code-generation architecture aligned with model-driven technologies, in particular the MDA (model-driven architecture) proposal. Finally, our proposal has been validated by means of a set of sample data sets from a well-known case study.     

Procedures for the forced,damped vibration analysis of structural frames using distributed parameter models

The paper summarises an approach to the forced vibration analysis of skeletal elastic structures, making use of “exact” matrix technique. The analysis is based on the modal superposition method, which has been developed in the context of models that retain characteristics of both distributed mass and stiffness. The free vibration analysis is performed using generalised dynamic stiffness functions appropriate to a Rayleigh-Timoshenko-Euler beam-column element. The contributions to dynamic displacements and dynamic internal forces by inertia effects during forced vibration are properly accounted for, and all results are obtained from explicit solutions to the relevant equations at all stages. Numerical integration or other approximate procedures are not required. It is the objective of the present paper to summarise procedures, numerical examples being available elsewhere (e.g. [1–3]). However, the paper is concluded with a practical example illustrating results obtainable by the techniques described below.     

Stability analysis for a class of linear controllers under control constraints

This paper presents a method of analyzing a system for stability when control magnitude constraints are introduced. Given a linear full state feedback controller (of a certain form) which stabilizes the system in the absence of control constraints, we then determine sufficient conditions under which the system with constrained control remains stable. To guarantee stability, there is a tradeoff between the size of the initial condition set and the size of the control constraints. Results are extended to systems with time varying uncertainty in the system matrix and input matrix.This research was supported by NASA Grant NGT-50551.     

Automated structural design and analysis of advanced composite wing models

The design of a composite wind tunnel model has demonstrated the ability to tailor the response of a composite structure to provide desired static and dynamic characteristics. This was possible because the strength and stiffness properties of composite structures can be controlled through selection of materials and lamination patterns. To take maximum advantage of the capability, efficient computer procedures are being developed for the design and analysis of composite structures. A finite element procedure and a direct Rayleigh-Ritz procedure, specialized for the preliminary analysis of wing-type structure, are discussed. The use and accuracy of these procedures have been demonstrated on a low cost, low risk basis in the design and analysis of a composite wind tunnel model and in test-theory correlation for static and dynamic response. Material selection, intermediate design decisions, fabrication, testing for natural modes and frequencies, and testing for influence coefficients for the wind tunnel model are discussed.