Towards a generic model for object-oriented information system modelling

With the proliferation of object-oriented methods for information systems design, and the terminology used by each one, an intermediate step is indispensable in the transition between the design and the different implementation environments. Regardless of any method, this step aims at the unification of all concepts in a generic model called MGCO2.     

A constraint-based dynamic geometry system

Dynamic geometry systems are tools for geometric visualization. They allow the user to define geometric elements, establish relationships between them and explore the dynamic behavior of the remaining geometric elements when one of them is moved. The main problem in dynamic geometry systems is the ambiguity that arises from operations that lead to more than one possible solution. Most dynamic geometry systems deal with this problem in such a way that the solution selection method leads to a fixed dynamic behavior of the system. This is specially annoying when the behavior observed is not the one the user intended.In this work we propose a modular architecture for dynamic geometry systems built upon a set of functional units which will allow us to apply some well-known results from the Geometric Constraint Solving field. A functional unit called filter will provide the user with tools to unambiguously capture the expected dynamic behavior of a given geometric problem.     

一种基于图分解的几何约束求解方法

为了提高几何约束求解的效率和鲁棒性 ,对基于图的构造方法进行了改进 ,即加入虚约束进行扩展和过约束问题的一致性判定 ,提出了一种基于图分解的方法 ,用此方法可以处理包括完全约束、过约束和欠约束等多种情况的约束求解问题 ,另外 ,在该方法中还通过引入分解树将约束求解的范围由整体下降到局部 ,使大部分求解过程能够采用几何求解实现 ,提高了求解和后续修改的效率 ,通过实验数据测试证明 ,该方法对于大型约束求解问题可以达到实时处理的效果 ,具有较强的实用性     

Revisiting decomposition analysis of geometric constraint graphs

Geometric problems defined by constraints can be represented by geometric constraint graphs whose nodes are geometric elements and whose arcs represent geometric constraints. Reduction and decomposition are techniques commonly used to analyze geometric constraint graphs in geometric constraint solving.In this paper we first introduce the concept of deficit of a constraint graph. Then we give a new formalization of the decomposition algorithm due to Owen. This new formalization is based on preserving the deficit rather than on computing triconnected components of the graph and is simpler. Finally we apply tree decompositions to prove that the class of problems solved by the formalizations studied here and other formalizations reported in the literature is the same.     

Towards a deductive object-oriented database language

A language for databases with sets, tuples, lists, object identity and structural inheritance is proposed. The core language is logic-based with a fixpoint semantics. Methods with overloading and methods evaluated externally providing extensibility of the language are considered. Other important issues such as updates and the introduction of explicit control are discussed.     

A Prototypical 3D Graphical Visualizer for Object-Oriented Systems

is paper describes a framework for visualizing object-oriented systems within a 3D interactive environment.The 3D visualizer represents the structure of a program as Cylinder Net that simultaneously specifies two relationships between objects within 3D virtual space.Additionally,it represents additional relationships on demand when objects are moved into local focus.The 3D visualizer is implemented using a 3D graphics toolkit,TOAST,that implements 3D Widgets 3D graphics to ease the programming task for 3D visualization.     

Specifying business rules in object-oriented analysis

A major purpose of analysis is to represent precisely all relevant facts, as they are observed in the external world. A substantial problem in object-oriented analysis is that most modelling languages are more suitable to build computational models than to develop conceptual models. It is a rather blind assumption that concepts that are convenient for design can also be applied during analysis. Preconditions, postconditions and invariants are typical examples of concepts with blurred semantics. At the level of analysis they are most often used to specify business rules. This paper introduces proper concepts for modelling business rules and specifies their semantics.     

Extending CSG with projections: Towards formally certified geometric modeling

We extend traditional Constructive Solid Geometry (CSG) trees to support the projection operator. Existing algorithms in the literature prove various topological properties of CSG sets. Our extension readily allows these algorithms to work on a greater variety of sets, in particular parametric sets, which are extensively used in CAD/CAM systems. Constructive Solid Geometry allows for algebraic representation which makes it easy for certification tools to apply. A geometric primitive may be defined in terms of a characteristic function, which can be seen as the zero-set of a corresponding system along with inequality constraints. To handle projections, we exploit the Disjunctive Normal Form, since projection distributes over union. To handle intersections, we transform them into disjoint unions. Each point in the projected space is mapped to a contributing primitive in the original space. This way we are able to perform gradient computations on the boundary of the projected set through equivalent gradient computations in the original space. By traversing the final expression tree, we are able to automatically generate a set of equations and inequalities that express either the geometric solid or the conditions to be tested for computing various topological properties, such as homotopy equivalence. We conclude by presenting our prototype implementation and several examples.     

TGMS: An object-oriented system for programming geometry

TGMS (tiered geometric modelling system) is an experimental system intended to reduce the difficulty and cost of developing new solid modelling applications while preserving investment in an existing, time-tested, solid modeller. The application developer writes programs in the TGMS language, which consists of a base language augmented by data types (classes) for geometry. The base programming language is AML/X, an object-oriented language intended for use in design and manufacturing applications. Solid modelling is done using an interface to GDP (geometric design processor), an existing, production-quality solid modelling system. TGMS shows how a system written in a non-object-oriented language can be used as a base for an object-oriented application programming environment. This paper presents the design of TGMS and discusses important aspects of its implementation. The TGMS language defines classes and methods that provide an interface to functions and data represented in a non-object-oriented language. To implement TGMS, issues related to communication, storage management and consistency were addressed. These, and other, implementation issues are discussed. The paper includes sample programs and a summary of feedback from TGMS users. It concludes that the use of object-oriented programming for geometry has many benefits, and that an object-oriented system can be built on top of a non-object-oriented system at less cost than building the equivalent object-oriented system from scratch.     

Interactive design of 3D models with geometric constraints

In this paper, an interactive graphical approach for the design of parameterized part-hierarchies is presented. Primitive solids can be grouped into compound objects, and multiple instances of a compound object can be used in further designs. Geometric relations between primitives and instances are specified by geometric constraints between their local coordinate systems. The user can specify and edit a model by direct manipulation on a perspective or parallel projection with a mouse, whereas a procedural model representations is automatically generated via visual programming. The obtained twoview approach offers two concurrent interface styles to the end-user and enables the combination of an intuitive direct manipulation interface with the expressiveness of a procedural modeling language.     

Automated production of traditional proofs in solid geometry

This paper presents a method of producing readable proofs for theorems in solid geometry. The method is for a class of constructive geometry statements about straight lines, planes, circles, and spheres. The key idea of the method is to eliminate points from the conclusion of a geometric statement using several (fixed) high-level basic propositions about the signed volumes of tetrahedrons and Pythagorean differences of triangles. We have implemented the algorithm, and more than 80 examples from solid geometry have been used to test the program. Our program is efficient and the proofs produced by it are generally short and readable.The work reported here was supported in part by the NSF Grant CCR-9117870 and Chinese National Science Foundation.On leave from Institute of Systems Sciences, Academia Sinica, Beijing 100080, P.R. China.     

Estimation of epipolar geometry by linear mixed-effect modelling

Epipolar geometry relies on the determination of the fundamental matrix. Classical approaches for estimating the fundamental matrix assume that a Gaussian distribution exists in the errors in view of mathematical tractability. However, this assumption will not be justified when the distribution computed is not normally distributed. We propose a new approach that does not make the Gaussian assumption, and so can attain robustness and accuracy in different conditions. The proposed framework, weighted least squares (WLS), is the application of linear mixed-effect models considering the correlation between different data subsamples. It provides an unbiased estimation of the fundamental matrix after mitigating the effects of outliers. We test the new model by using synthetic and real images, and comparing it to standard methods.     

PROTOB: An object-oriented case tool for modelling and prototyping distributed systems

The PROTOB object-oriented methodology for the executable specification of large-scale event-driven systems is introduced and described. Two supporting features of PROTOB are also presented: the graphic and textual language that formally describes the behaviour of objects, which is based on high-level Petri nets called “PROT nets” and which is demonstrated to be more powerful than SA/RT dataflows; and a CASE environment with tools for specification, modelling, simulation and prototyping. Use of PROTOB is illustrated by discussion of the automated generation of distributed systems running on a network of VMS and UNIX computers.     

基于Web的动态几何软件领域模型及其应用

动态几何软件以其动态、直观的特点广泛应用于几何约束作图。针对数据结构缺乏对动态几何领域内可复用的抽象描述的问题,提出一种动态几何软件领域模型的设计方法。首先经过领域分析来识别并划分出最基本的上下文边界,然后通过领域模型设计得到动态几何软件核心领域模型,最后在体系结构建模过程中,在纵向与横向两个维度对动态几何软件进行解耦。实验结果表明,利用该领域模型设计方法研发的动态几何软件能正确地处理图形在临界位置退化的情形。该模型表达的领域知识同时适用于二维及三维的动态几何软件,并支持对不同设备分别设计布局与交互,实现了领域知识的高层次复用。     

Improving the applicability of object-oriented class cohesion metrics

Context

Class cohesion is an important object-oriented quality attribute. It refers to the degree of relatedness between the methods and attributes of a class. Several metrics have been proposed to measure the extent to which the class members are related. Most of these metrics have undefined values for a relatively high percentage of classes, which limits their applicability. The classes that have undefined values lack methods, attributes, or parameter types, or they include only a single method.

Objective

We improve the applicability of the class cohesion metrics by defining their values for such special classes. In addition, we theoretically and empirically validate the improved metrics.

Method

We theoretically examine whether the defined values satisfy the key cohesion properties. In addition, we empirically validate the metrics before and after the improvements to test whether the defined values improve the ability of the metrics to evaluate class cohesion. We also explore the correlation between the metrics and the presence of faulty classes to indirectly determine the strength or weakness of the metrics in indicating class quality.

Results

The results show that our assigned values for the undefined cases do not violate the key cohesion properties and considerably improve the ability of the metrics to explain the presence of faulty classes and may therefore improve their ability to indicate the quality of the class design.

Conclusions

Having the class cohesion metrics defined for all possible cases improves the applicability of the metrics and potentially increases their precision in indicating class quality.     

Using NNF to transform conceptual data models to object-oriented database designs

More work is needed on devising practical, but theoretically well-founded procedures for doing object-oriented database (OODB) design [17]. Design procedures should also be flexible enough to take into account various application characteristics (such as whether objects are very large or are read-only). In this paper, we present and discuss an OODB design procedure that addresses these problems. The procedure is practical in the sense that it is based on a common family of conceptual models and in the sense that it does not expect users to supply esoteric, difficult-to-discover, and hard-to-understand constraints (such as multivalued dependencies), nor does it make hard-to-check and easy-to-overlook assumptions (such as the universal relation scheme assumption). At the same time, the procedure is well-founded and formal, being based on NNF (Nested Normal Form [21]), a new theoretical result that characterizes properties of interest in designing complex objects. It is also adaptable to various applications characteristics.     

The design of an object-oriented command interpreter

Object-oriented programming languages are noted for their ability to allow users quickly to construct large software systems. They achieve this ability by allowing the programmer to concentrate on what it is they want to do, ignoring details of how that functionality is achieved. Such characteristics should make the object-oriented style of programming attractive to casual or novice computer users, indeed one of the best known object-oriented programming languages, Smalltalk, was initially designed with just such novice users in mind. The Unix operating system is widely regarded as a good environment for doing software development. Nevertheless, its large number of often terse and cryptic commands make it difficult for novice or casual users to use. In this paper we argue that one solution is to create an object-oriented command interpreter, or shell, between the user and the underlying system. This paper reports on the construction of one such prototype shell, and the lessons we have learned from the use of this system.