Christoph Quix

Architecture and quality in data warehouses: An extended repository approach

Abstract Most database researchers have studied data warehouses (DW) in their role as buffers of materialized views, mediating between update-intensive OLTP systems and query-intensive decision support. This neglects the organizational role of data warehousing as a means of centralized information flow control. As a consequence, a large number of quality aspects relevant for data warehousing cannot be expressed with the current DW meta models. This paper makes two contributions towards solving these problems. Firstly, we enrich the meta data about DW architectures by explicit enterprise models. Secondly, many very different mathematical techniques for measuring or optimizing certain aspects of DW quality are being developed. We adapt the Goal-Question-Metric approach from software quality management to a meta data management environment in order to link these special techniques to a generic conceptual framework of DW quality. The approach has been implemented in full on top of the ConceptBase repository system and has undergone some validation by applying it to the support of specific quality-oriented methods, tools, and application projects in data warehousing.

Industrial-strength schema matching

Schema matching identifies elements of two given schemas that correspond to each other. Although there are many algorithms for schema matching, little has been written about building a system that can be used in practice. We describe our initial experience building such a system, a customizable schema matcher called Protoplasm.

Towards quality-oriented data warehouse usage and evolution

As a decision support information system, a data warehouse must provide high level quality of data and quality of service. In the DWQ project we have proposed an architectural framework and a repository of metadata which describes all the data warehouse components in a set of metamodels to which is added a quality metamodel, defining for each data warehouse metaobject the corresponding relevant quality dimensions and quality factors. Apart from this static definition of quality, we also provide an operational complement, that is a methodology on how to use quality factors and to achieve user quality goals. This methodology is an extension of the Goal-Question-Metric (GQM) approach, which allows to capture (a) the inter-relationships between different quality factors and (b) to organize them in order to fulfil specific quality goals. After summarizing the DWQ quality model, this paper describes the methodology we propose to use this quality model, as well as its impact on the data warehouse evolution.

Design and Analysis of Quality Information for Data Warehouses

Data warehouses are complex systems that have to deliver highly-aggregated, high quality data from heterogeneous sources to decision makers. Due to the dynamic change in the requirements and the environment, data warehouse system rely on meta databases to control their operation and to aid their evolution. In this paper, we present an approach to assess the quality of the data warehouse via a semantically rich model of quality management in a data warehouse. The model allows stakeholders to design abstract quality goals that are translated to executable analysis queries on quality measurements in the data warehouses meta database. The approach is being implemented using the ConceptBase meta database system.

Business data management for business-to-business electronic commerce

Business-to-business electronic commerce (B2B EC) opens up new possibilities of trade. For example, new business partners from around the globe can be found, their offers can be compared, even complex negotiations can be conducted electronically, and a contract can be drawn up and fulfilled via an electronic marketplace. However, a sophisticated data management is required to provide such factilities. In this paper, the results of a multi-national project on creating a business-to-business electronic marketplace for small and medium-sized enterprises are presented. Tools for information discovery, protocol-based negotiations, and monitored contract enactment are provided and based on a business data repository. The repository integrates heterogeneous business data with business communication. Specific problems such as multi-linguality, data ownership, and traceability of contracts and related negotiations are addressed and it will be shown that the present approach provides efficient business data management for B2B EC.

Data warehouse process management

Abstract Previous research has provided metadata models that enable the capturing of the static components of a data warehouse architecture, along with information on different quality factors over these components. This paper complements this work with the modeling of the dynamic parts of the data warehouse. The proposed metamodel of data warehouse operational processes is capable of modeling complex activities, their interrelationships, and the relationship of activities with data sources and execution details. Moreover, the metamodel complements the existing architecture and quality models in a coherent fashion, resulting in a full framework for quality-oriented data warehouse management, capable of supporting the design, administration and especially evolution of a data warehouse. Finally, we exploit our framework to revert the widespread belief that data warehouses can be treated as collections of materialized views. We have implemented this metamodel using the language Telos and the metadata repository system ConceptBase.

DOC.COM: a framework for effective negotiation support in electronic marketplaces

Abstract Today, research in electronic negotiations focuses on negotiation protocols that support the negotiation of only a few properties. These protocols are mainly designed for automated negotiations between software agents. However, for peer-to-peer negotiations in business-to-business electronic marketplaces, such protocols are less appropriate. For example, negotiations about multiple attributes, complex attribute combinations, or frame contracts require more sophisticated support of the involved interactions and communication acts. In this paper we present a novel approach to the effective support of electronic negotiations among human negotiators. Our approach is based on the following observation. The outcome of a successful negotiation process is a business contract. The contract evolves during the negotiation, coordinated through the exchange of structured messages such as offers, requests, quotations, counteroffers, and acceptances. Therefore, each negotiation between business partners involves the exchanges of documents and messages. Furthermore, documents and messages are interrelated in that a message leads to a new contract version which itself is the medium for a new negotiation step and thus initiates a new message. In contrast to the current practice of separate management of messages and documents, we create a powerful framework for effective negotiation support in electronic marketplaces by combining communication and document management. Our approach enables monitoring of contractual obligations and traceability of both documents and messages and their interrelations.

GeRoMe : a generic role based metamodel for model management

The goal of Model Management is the development of new technologies and mechanisms to support the integration, evolution and matching of models. Such tasks are to be performed by means of a set of model management operators which work on models and their elements, without being restricted to a particular metamodel (e.g. the relational or UML metamodel). We propose that generic model management should employ a generic metamodel (GMM) which serves as an abstraction of the features of particular metamodels while preserving the semantics of its different elements. A naive generalization of the elements of concrete metamodels in generic metaclasses would loose some of the specific features of the metamodels, or yield a prohibitive number of metaclasses in the GMM. To avoid these problems, we propose the Generic Role Based MetamodelGeRoMe in which each model element is decorated with a set of role objects that represent specific properties of the model element. Roles may be added to or removed from elements at any time, which enables a very flexible and dynamic yet accurate definition of models. Roles constitute to operators different views on the same model element. Thus, operators concentrate on features which affect their functionality but may remain agnostic about other features. Consequently, these operators can use polymorphism and have to be implemented only once using GeRoMe, and not for each specific metamodel. We verified our results by implementing GeRoMe and a selection of model management operators using our metadata system ConceptBase.

Architecture and Quality in Data Warehouses

Most database researchers have studied data warehouses (DW) in their role as buffers of materialized views, mediating between updateintensive OLTP systems and query-intensive decision support. This neglects the organizational role of data warehousing as a means of centralized information flow control. As a consequence, a large number of quality aspects relevant for data warehousing cannot be expressed with the current DW meta models. This paper makes two contributions towards solving these problems. Firstly, we enrich the meta data about DW architectures by explicit enterprise models. Secondly, many very different mathematical techniques for measuring or optimizing certain aspects of DW quality are being developed. We adapt the Goal-Question-Metric approach from software quality management to a meta data management environment in order to link these special techniques to a generic conceptual framework of DW quality. Initial feedback from ongoing experiments with a partial implementation of the resulting meta data structure in three industrial case studies provides a partial validation of the approach.

Generic schema merging

Schema merging is the process of integrating several schemas into a common, unified schema. There have been various approaches to schema merging, focusing on particular modeling languages, or using a lightweight, abstract metamodel. Having a semantically rich representation of models and mappings is particularly important for merging as semantic information is required to resolve the conflicts encountered. Therefore, our approach to schema merging is based on the generic role-based metamodel GeRoMe and intensional mappings based on the real world states of model elements. We give a formal definition of the merged schema and present an algorithm implementing these formalizations.