An approach to engineering the requirements of data warehouses

We focus exclusively on the issue of Requirements engineering for Data Warehouses (DW). Our position is that the information content of a DW is found in the larger context of the goals of an organization. We refer to this context as the organizational perspective. Goals identify the set of decisions that are relevant which in turn help in determining the information needed to support these. The organizational perspective is converted into the technical perspective, which deals with the set of decisions to be supported and the information required. The latter defines Data warehouse contents. To elicit the technical perspective, we use the notion of an informational scenario. It is a typical interaction between a DW system and the decision maker and consists of a sequence of pairs of the form, <information request, response>. We formulate an information request as a statement in an adapted form of SQL called Specification SQL. The proposals here are implemented in the form of an Informational Scenario Engine that processes informational scenarios and determines Data Warehouse Information Contents.     

Two approaches to the integration of heterogeneous data warehouses

In this paper we address the problem of integrating independent and possibly heterogeneous data warehouses, a problem that has received little attention so far, but that arises very often in practice. We start by tackling the basic issue of matching heterogeneous dimensions and provide a number of general properties that a dimension matching should fulfill. We then propose two different approaches to the problem of integration that try to enforce matchings satisfying these properties. The first approach refers to a scenario of loosely coupled integration, in which we just need to identify the common information between data sources and perform join operations over the original sources. The goal of the second approach is the derivation of a materialized view built by merging the sources, and refers to a scenario of tightly coupled integration in which queries are performed against the view. We also illustrate architecture and functionality of a practical system that we have developed to demonstrate the effectiveness of our integration strategies. A preliminary version this paper appeared, under the title “Integrating Heterogeneous Multidimensional Databases” [9], in 17th Int. Conference on Scientific and Statistical Database Management, 2005.     

Supporting the design of office layout meeting ergonomics requirements

This paper proposes a method and an information technology tool aiming to support the ergonomics layout design of individual workstations in a given space (building). The proposed method shares common ideas with previous generic methods for office layout. However, it goes a step forward and focuses on the cognitive tasks which have to be carried out by the designer or the design team trying to alleviate them. This is achieved in two ways: (i) by decomposing the layout design problem to six main stages, during which only a limited number of variables and requirements are considered and (ii) by converting the ergonomics requirements to functional design guidelines. The information technology tool (ErgoOffice 0.1) automates certain phases of the layout design process, and supports the design team either by its editing and graphical facilities or by providing adequate memory support.     

Spatial data warehouses and spatial OLAP come towards the cloud: design and performance

Cloud computing systems handle large volumes of data by using almost unlimited computational resources, while spatial data warehouses (SDWs) are multidimensional databases that store huge volumes of both spatial data and conventional data. Cloud computing environments have been considered adequate to host voluminous databases, process analytical workloads and deliver database as a service, while spatial online analytical processing (spatial OLAP) queries issued over SDWs are intrinsically analytical. However, hosting a SDW in the cloud and processing spatial OLAP queries over such database impose novel obstacles. In this article, we introduce novel concepts as cloud SDW and spatial OLAP as a service, and afterwards detail the design of novel schemas for cloud SDW and spatial OLAP query processing over cloud SDW. Furthermore, we evaluate the performance to process spatial OLAP queries in cloud SDWs using our own query processor aided by a cloud spatial index. Moreover, we describe the cloud spatial bitmap index to improve the performance to process spatial OLAP queries in cloud SDWs, and assess it through an experimental evaluation. Results derived from our experiments revealed that such index was capable to reduce the query response time from 58.20 up to 98.89 %.     

Supporting the acquisition and modeling of requirements in software design

This paper describes a system for supporting the construction of software requirement models, which are initial computable models representing users' requirements in software design. The system principally consists of two components, a system for aiding the formation of requirement concepts by visualizing a user's thought space, and a knowledge-based system which automatically assembles the ascertained requirement concepts into a requirement model. The system extracts reusable components of a requirement model, corresponding to the users' abstract requirement concept, from a store of similar past cases. The components are then automatically arranged using heuristic reasoning. By using the system, users can make their requirement concepts more mature, and simultaneously get computable requirement models as by-products.     

Multimedia data warehouses: a multiversion model and a medical application

Histogram feature representation is important in many classification applications for characterization of the statistical distribution of different pattern attributes, such as the color and edge orientation distribution in images. While the construction of these feature representations is simple, this very simplicity may compromise the classification accuracy in those cases where the original histogram does not provide adequate discriminative information for making a reliable classification. In view of this, we propose an optimization approach based on evolutionary computation (Back, Evolutionary algorithms in theory and practice, Oxford University Press, New York, 1996; Fogel, Evolutionary computation: toward a new philosophy of machine intelligence, 2nd edn. IEEE, Piscataway, NJ 1998) to identify a suitable transformation on the histogram feature representation, such that the resulting classification performance based on these features is maximally improved while the original simplicity of the representation is retained. To facilitate this optimization process, we propose a hierarchical classifier structure to demarcate the set of categories in such a way that the pair of category subsets with the highest level of dissimilarities is identified at each stage for partition. In this way, the evolutionary search process for the required transformation can be considerably simplified due to the reduced level of complexities in classification for two widely separated category subsets. The proposed approach is applied to two problems in multimedia data classification, namely the categorization of 3D computer graphics models and image classification in the JPEG compressed domain. Experimental results indicate that the evolutionary optimization approach, facilitated by the hierarchical classification process, is capable of significantly improving the classification performance for both applications based on the transformed histogram representations.

Identifying requirements for communication support: A maturity grid-inspired approach

Communication is a critical success factor in design. It can be seen as the social and cognitive process by which information is selected, messages are exchanged between interacting partners, and meaning is created. How communication processes can best be captured, analysed and assessed, as a preliminary step toward suggestions for improvement of communication practices, remains a challenge for researchers and practitioners. To this end, a maturity grid-inspired approach to audit communication practices has been developed. This paper employs a maturity grid approach and reflects critically on the construction and application of the approach in a structured group workshop in software design. Such an approach yields dual benefits: (a) as a research method to gather insight into communication and (b) as a guide to plan improvements in practice. Conclusions are drawn for the process of auditing communication in design.     

From requirements to implementations: a model-driven approach for web development

Model-Driven Development (MDD) is an appropriate paradigm for web development since interoperability and flexibility are required to cope with implementation technologies and functionalities that are in permanent evolution. In this paper, we describe and illustrate the MDD process of the ADM (Ariadne Development Method) hypermedia/web engineering method. The two cornerstones of the ADM are the Labyrinth++ meta-meta-model, which formalizes the core constructs used within all the design meta-models, and the meta-meta-model specification as an ontology that provides semantics and reasoning not only for model transformations but also for consistency checking and model validation. These features have been essential in the development of a CASE tool, called AriadneTool that supports the different abstract levels of modeling, model transformations as well as the generation of light prototypes in different web implementation technologies.     

Economic sizing of warehouses: A linear programming approach

Determining the best size for a private warehouse is a planning problem which can affect the overall operations of the firm for many years into the future. A linear programming formulation is presented which determines the optimal size warehouse to construct when demand is highly seasonal and public warehouse space is available on a monthly basis. The model is then extended for the dynamic sizing problem in which the warehouse size is allowed to change over time.     

Supporting user participation design using a fuzzy analytic hierarchy process approach

There are three fundamental problems that may occur in the process of user participation design: first, the participants/users may not be able to express their requirements clearly; second, they have little knowledge about design; and third, they are generally unfamiliar with the software that designers use. Based on this understanding, a method that considers design rationale is proposed in this work to support the process of user participation design. In addressing the user participation process, a fuzzy analytic hierarchy process (AHP) approach is applied to grasp people's ideas, in the initial design phase. A case study on creating house layout design is employed to illustrate the proposed approach. In this regard, to help participants/users create layout designs, it is proposed that a 3D generative system is used, which integrates navigational concepts, direct manipulation, and the design rationale theory. In a nutshell, this research proposes a system to implement a design rational model and improve design communication in the user participation process. To demonstrate the effectiveness of the proposed prototype system, a user test is performed and we put forward some findings and research questions for further research and industry practices.     

A trace metamodel proposal based on the model driven architecture framework for the traceability of user requirements in data warehouses

The complexity of the data warehouse (DW) development process requires to follow a methodological approach in order to be successful. A widely accepted approach for this development is the hybrid one, in which requirements and data sources must be accommodated to a new DW model. The main problem is that we lose the relationships between requirements, elements in the multidimensional (MD) conceptual models and data sources in the process, since no traceability is explicitly specified. Therefore, this hurts requirements validation capability and increases the complexity of Extraction, Transformation and Loading processes. In this paper, we propose a novel trace metamodel for DWs and focus on the relationships between requirements and MD conceptual models. We propose a set of Query/View/Transformation rules to include traceability in DWs in an automatic way, allowing us to obtain a MD conceptual model of the DW, as well as a trace model. Therefore, we are able to trace every requirement to the MD elements, further increasing user satisfaction. Finally, we show the implementation in our Lucentia BI tool.     

全相联异构数据集成系统的研究和设计

本文介绍了在建设出入境人员健康状况实时监测网络采用的基于Web Services的全相联异构数据集成方案,该方案利用Web Services的跨平台等特点,综合了数据仓库和虚拟数据库在异构数据集成中的优点,通过设计领域字典表及字段、量纲等映射表,有效地解决了异构数据集成中的环境异构和数据异构等问题,并从异构数据转化、全局查询等方面阐述了该方案的实现过程。实践表明,该方案对了分布式异构数据的共享问题解决具有可行性和高效性。     

Logical data base design: A management-oriented approach

A logical data base consists of data definitions and data relationships. It is typically very large and complex even for a small organization, but it is generally designed in an ad hoc manner. However, several approaches have recently been proposed that allow for a systematic logical data base design.To make a data base more useful to the managers, it is imperative to encourage and obtain their involvement in the initial phase of the logical data base design. “Surface semantic models” are used in the logical data base design process to increase this involvement. A special type of this, called a “hierarchical external view model”, is proposed. It has been successfully used to develop a logical data base for the Department of Aging in Pennsylvania.     

A method to elicit architecturally sensitive usability requirements: its integration into a software development process

In the Human-Computer Interaction (HCI) community, software usability has primarily been concerned with the presentation of information, more precisely with the user interface. However, some usability problems can prove costly to fix if the changes require modifications that reach beyond the presentation layer, namely those that cannot be easily accommodated by the software architecture. Taking into account some usability requirements earlier in the software development cycle, specifically prior to the architectural design phase, can reduce the cost of these modifications. There is a scarcity of methods and guidelines with the scope to direct users in eliciting the usability requirements that can impact the software architecture. This paper proposes a usability-driven adaptation of the quality attribute workshop (QAW) to assist software development organizations in discovering and documenting usability requirements. It shows how this method can be integrated into a software development process, by discussing how the existing software framework workflows can be adjusted to take this new activity into consideration. A preliminary exercise was conducted to help discern the utility and the limits of the proposed method. Participants with different levels of knowledge of usability and comprehension of the system being developed found the method constructive, as it guided them in identifying the architecturally relevant usability requirements. It also helped determine the usability aspects that would not necessarily have been defined if this technique had not been employed.     

The SB-index and the HSB-index: efficient indices for spatial data warehouses

Spatial data warehouses (SDWs) allow for spatial analysis together with analytical multidimensional queries over huge volumes of data. The challenge is to retrieve data related to ad hoc spatial query windows according to spatial predicates, avoiding the high cost of joining large tables. Therefore, mechanisms to provide efficient query processing over SDWs are essential. In this paper, we propose two efficient indices for SDW: the SB-index and the HSB-index. The proposed indices share the following characteristics. They enable multidimensional queries with spatial predicate for SDW and also support predefined spatial hierarchies. Furthermore, they compute the spatial predicate and transform it into a conventional one, which can be evaluated together with other conventional predicates by accessing a star-join Bitmap index. While the SB-index has a sequential data structure, the HSB-index uses a hierarchical data structure to enable spatial objects clustering and a specialized buffer-pool to decrease the number of disk accesses. The advantages of the SB-index and the HSB-index over the DBMS resources for SDW indexing (i.e. star-join computation and materialized views) were investigated through performance tests, which issued roll-up operations extended with containment and intersection range queries. The performance results showed that improvements ranged from 68% up to 99% over both the star-join computation and the materialized view. Furthermore, the proposed indices proved to be very compact, adding only less than 1% to the storage requirements. Therefore, both the SB-index and the HSB-index are excellent choices for SDW indexing. Choosing between the SB-index and the HSB-index mainly depends on the query selectivity of spatial predicates. While low query selectivity benefits the HSB-index, the SB-index provides better performance for higher query selectivity.     

Fuzzy arithmetic based reliability allocation approach during early design and development

During early design and development stages, every engineering system has to meet its specific reliability goals. The target reliability of the system is achieved through application of an effective reliability apportionment technique to its subsystems. There are various traditional methods exist to perform the reliability allocation based on engineering factors that are assessed in a subjective manner. The conventional reliability allocation approach requires the assessment of factors like complexity, cost, and maintenance. This may not be realistic in real applications if they are assessed in a crisp manner by the domain experts of their varied expertise and background.In this paper, we treat allocation factors as fuzzy numbers, which are evaluated in fuzzy linguistic terms. As a result, fuzzy proportionality factor scales are proposed for the subsystems. In order to accomplish fuzzy division to evaluate the fuzzy proportionality factor, an approximation method based on linear programming for trapezoidal fuzzy numbers is also proposed in this paper. For the evaluation of weighting factors from fuzzy proportionality factors, centroid method of defuzzification is being employed. The allocated reliability of each subsystem is computed with the help of weighting factor thereafter. An example is provided to illustrate the potential application of the proposed fuzzy based reliability allocation approach.