TIME-ROLLBACK USING LOGS IN HISTORICAL DATABASES

A temporal database supports both real-world (i.e. valid) time and transaction time, and provides the rollback capability. A historical database, on the other hand, supports only the valid time. The paper shows that the rollback capability can be provided for the historical databases by making use of logs, and this is proposed as an efficient alternative to implement temporal databases. The proposed method is shown to be more efficient when the number of rollback queries is not high. Algorithms are presented to apply corrections to the historical databases and for the rollback operation

Effort drivers in maintenance outsourcing-an experiment using Taguchi's methodology

We establish the context of software maintenance outsourcing of large commercial systems and discuss the problem of estimating the maintenance effort in absence of key parameters such as development effort and maintenance history. To arrive at the drivers that could have a significant effect on the maintenance effort, an experiment was conducted at Syntel, a NASDAQ listed application management and e-business solutions company. We present the list of possible drivers, the profile of the people who participated in the experiment, the details of the 36 experiments and the statistical analysis of the experiment based on Taguchi's methodology. For a system whose size parameter in terms of lines of code is known, we conclude that the five most significant parameters that effect the efforts of maintenance are a)the multi time zone support, b)average number of lines per program, c)percentage of online programs in the total system, d)the nature of service level agreements and e)the complexity of the file system being used.© IEE

Evaluating relative contributions of various HCI activities to usability

Several activities related to human-computer interaction (HCI) design are described in literature. However, it is not clear whether each HCI activity is equally important. We propose a multi-disciplinary framework to organise HCI work in phases, activities, methods, roles, and deliverables. Using regression analyses on data from 50 industry projects, we derive weights for the HCI activities in proportion to the impact they make on usability, and compare these with the recommended and assigned weights. The scores of 4 HCI activities (user studies, user interface design, usability evaluation of the user interface, and development support) have the most impact on the Usability Goals Achievement Metric (UGAM) and account for 58% of variation in it

Modeling of building evacuation using ladders

Existing research and tools used for building evacuation planning do not take into account the common practice of using ladders for rescue operations. The ladders provide a simple and practical way of creating additional exits with a potential to significantly reduce the evacuation time. Use of ladders is critical in case of severe disasters and when some normal exits get blocked. To our knowledge, this paper presents the first systematic planning approach for optimal placement of a limited number of available ladders. We first propose modifications to the existing models of buildings to incorporate ladders and ladder points (locations in the building where ladders can be placed). Next, we develop optimization formulations to solve the following evacuation planning problems when a limited number of ladders are available: (i) optimal deployment of a given number of ladders to minimize evacuation time and (ii) finding minimum number of ladders along with their locations necessary to evacuate a building in a given evacuation time. These problems, posed as integer linear programming formulations, are applied to two case studies to demonstrate the importance of using ladders. The results show that evacuation plans can be significantly improved by optimally placing ladders at the selected ladder points. (C) 2012 Elsevier Ltd. All rights reserved

An adaptive algorithm for incremental mining of association rules

The association rules represent an important class of knowledge that can be discovered from data warehouses. Current research efforts are focused on inventing efficient ways of discovering these rules from large databases. As databases grow, the discovered rules need to be verified and new rules need to be added to the knowledge base. Since mining afresh every time the database grows is inefficient, algorithms for incremental mining are being investigated. Their primary aim is to avoid or minimize scans of the older database by using the intermediate data constructed during the earlier mining. We present one such algorithm. We make use of large and candidate itemsets and their counts in the older database, and scan the increment to find which rules continue to prevail and which ones fail in the merged database. We are also able to find new rules for the incremental and updated database. The algorithm is adaptive in nature, as it infers the nature of the increment and avoids altogether if possible, multiple scans of the incremental database. Another salient feature is that it does not need multiple scans of the older database. We also indicate some results on its performance against synthetic data.© IEE

A SELECTIVE ENUMERATION BASED HEURISTIC FOR RULE ALLOCATION

A distributed deductive database system consists of many autonomous deductive database systems connected by a computer network to facilitate sharing of both database and rules. The design of a distributed deductive database system differs from the design of conventional nondistributed deductive database systems. The former requires design of distribution of both the database and rulebase, whereas the latter requires design of data distribution. The paper addresses the problem of allocating rules in a distributed deductive database system, where rulebase (a collection of rules) and database are shared across autonomous sites. The problem is relevant and challenging in applications involving large rulebases. We have identified communication cost as the primary consideration in allocation of rules. The optimal allocation of rules over a set of sites is an NP-complete problem. It has prohibitive execution time for large rulebases. In this paper, we propose an efficient heuristic algorithm for non-replicated rule allocation and study its performance vis-a-vis the enumerative algorithm for optimal allocation. A heuristic for replicated allocation of rules is also presented which starts from the non-replicated allocation

Applicability of IEEE maintenance process for corrective maintenance outsourcing-an empirical study

We establish the context of maintenance outsourcing of mission critical applications by Fortune 500 organizations. We present the results of empirical studies that were conducted at Syntel, a NASDAQ listed application management and e-business solutions company, on 46 software maintenance projects that belonged to various lines of business on the IBM mainframe platform using an automated data collection tool EQUIP. After establishing that corrective maintenance activities form a significant component of the overall maintenance efforts, we examine the applicability of the IEEE standard maintenance process for corrective maintenance by measuring the efforts spent on the various activities. We conclude that (a) the processes for each type of maintenance need to be fine tuned especially in the context of outsourcing (b) analysis, testing form significant part of the corrective maintenance effort (c) teams need to carry out other activities such as database reorganization and configuration management that are not defined by the IEEE maintenance process.© IEE

Execution model for outsourced corrective maintenance

We focus on corrective maintenance carried out in the outsourced mode under strict service level agreements and present the characteristics of the problem and the activities performed. We detail the information requirements for various maintenance services, such as, emergency maintenance, production support, and corrective maintenance. We present the concept of a system execution model with its constituent nodes and arcs and present the steps to build the same. We present a case study of a large commercial outsourcing project to demonstrate how the execution model can help in making quick decisions that reduces the turn around times of corrective maintenance requests.© Elsevie