45241819
Minimum Networks in Uniform Orientation Metrics
In this paper we use the variational method to systematically study properties of minimum networks connecting any given set of points (called terminals) in a $\lambda$-plane, in which all lines are in $\lambda$ uniform orientations $i\pi /\lambda\ (0\le i<\lambda )$. We prove a number of angle conditions for Steiner minimum $\lambda$-trees, which are similar to the ones in the Euclidean case. In particular, we show that there exists a Steiner minimum $\lambda$-tree whose minimum angles at Steiner points are $\lfloor 2\lambda /3\rfloor\pi /\lambda$ and whose maximum angles are $\lceil 2\lambda /3\rceil\pi /\lambda$. We also investigate the assignment of nonstraight edges and unequal angles in Steiner minimum $\lambda$-trees, and we prove that there exists a Steiner minimum $\lambda$-tree in which every full component has at most one nonstraight edge. From these properties we are able to devise a number of finite methods for constructing Steiner minimum $\lambda$-trees. One of these methods is based on using algorithms for finding graphical Steiner minimum trees, and the other uses a generalization of the method of Melzak for Euclidean Steiner trees.
22841183
Graham's problem on shortest networks for points on a circle
Suppose a configurationX consists ofn points lying on a circle of radiusr. If at most one of the edges joining neighboring points has length strictly greater thanr, then the Steiner treeS consists of all these edges with a longest edge removed. In order to showS is, in fact, just the minimal spanning treeT, a variational approach is used to show the Steiner ratio for this configuration is at least one and equals one only ifS andT coincide. The variational approach greatly reduces the number of possible Steiner trees that need to be considered.
1209785
Ubiquitous applications: embedded systems to mainframe
Over the last 10 years, Smalltalk has moved from the “Parc” to Main Street as a standard object-oriented (OO) fifth generation language (5GL) for enterprise computing. To meet the needs of application developers, Smalltalk environments and tools have matured from the original research implementations to full-featured, multiplatform development environments. A recent study of development tools conducted by Software Productivity Research in Massachusetts for a software productivity consortium ranked Smalltalk first in most categories. What is surprising about this study is the application: a demanding telephone switch traditionally dominated by C or proprietary talc languages such as Chill, Protel, and Plex. The fact that Smalltalk ranked so highly is a testimony that Smalltalk is an application 5GL that scales. This article discusses the major technical challenges addressed by Smalltalk implementors and application developers working on a wide spectrum of applications.
2028674
An Exemplar Based Smalltalk
Two varieties of object-oriented systems exist: one based on classes as in Smalltalk and another based on exemplars (or prototypical objects) as in Act/1. By converting Smalltalk from a class based orientation to an exemplar base, independent instance hierarchies and class hierarchies can be provided. Decoupling the two hierarchies in this way enables the user's (logical) view of a data type to be separated from the implementer's (physical) view. It permits the instances of a class to have a representation totally different from the instances of a superclass. Additionally, it permits the notion of multiple representations to be provided without the need to introduce specialized classes for each representation. In the context of multiple inheritance, it leads to a novel view of inheritance (or-inheritance) that differentiates it from the more traditional multiple inheritance notions (and-inheritance). In general, we show that exemplar based systems are more powerful than class based systems. We also describe how an existing class based Smalltalk can be transformed into an exemplar-based Smalltalk and discuss possible approaches for the implementation of both and-inheritance and or-inheritance.
34406304
Agile Experiences
The proponents of various Agile Methodologies often share anecdotal evidence about how their favorite methodologies work. Come to this panel to hear first-hand experiences of those who have applied these methodologies in their organizations.
32027945
The Deplorable State of Class Libraries
Various efforts made to redesign and implement important class libraries are discussed. ClassLibs.com is a company dedicated to producing well-engineered quality class libraries and associated compliance test suites with related services. It also provides support, training and customization as additional for fee services. The major vendors have licensed the libraries ensuring that ClassLilbs.com will be able to continue to produce high quality libraries.
41519577
Anonymizing Tables
We consider the problem of releasing tables from a relational database containing personal records, while ensuring individual privacy and maintaining data integrity to the extent possible. One of the techniques proposed in the literature is k-anonymization. A release is considered k-anonymous if the information for each person contained in the release cannot be distinguished from at least k–1 other persons whose information also appears in the release. In the k-Anonymityproblem the objective is to minimally suppress cells in the table so as to ensure that the released version is k-anonymous. We show that the k-Anonymity problem is NP-hard even when the attribute values are ternary. On the positive side, we provide an O(k)-approximation algorithm for the problem. This improves upon the previous best-known O(klog k)-approximation. We also give improved positive results for the interesting cases with specific values of k — in particular, we give a 1.5-approximation algorithm for the special case of 2-Anonymity, and a 2-approximation algorithm for 3-Anonymity.