The design space for representing temporal data in XML has thus far received limited empirical attention. As a result, designers do not fully understand the design space and trade-offs between various representational approaches. This thesis presents an initial characterization of that design space and provides a qualitative and quantitative analysis of the extreme ends of the spectrum, as well as an expressive language for describing temporal data. We extend an existing language, τXSchema, to implement three classes of representations and show that the edit-based scheme provides the best performance in terms of creation time and representation size, although the item-based and sliced-based schemes can be validated more quickly. We also provide an analysis of where temporal constraint functionality should be implemented and show that, with a few exceptions, temporal constraint functionality must be implemented within the tools and cannot be implemented in the representational schema. These results provide insight into the overall design space for temporal representations that will be useful to researchers, tool implementers, and users of τXSchema.

Abstract-If past versions of XML documents are retained, what of the various integrity constraints defined in XML Schema on those documents? This paper describes how to interpret such constraints as sequenced constraints, applicable at each point in time. We also consider how to add new variants that apply across time, so-called non-sequenced constraints. Our approach supports temporal documents that vary over both valid and transaction time, whose schema can vary over transaction time. We do this by replacing the schema with a (possibly time-varying) temporal schema and replacing the document with a temporal document, both of which are upward compatible with conventional XML and with conventional tools like XMLLINT, which we have extended to support the temporal constraints introduced here.

Abstract. Database schemas are an integral part of many information systems (IS). New software-engineering methods, such as software product lines, allow engineers to create a high number of different programs tailored to the customer needs from a common code base. Unfortunately, these engineering methods usually do not take the database schema into account. Particularly, a tailored client program requires a tailored database schema as well to form a consistent IS. In this paper, we show the challenges of tailoring relational database schemas in software product lines. Furthermore, we present an approach to treat the client and database part of an IS in the same way using a variable database schema. Additionally, we show the benefits and discuss disadvantages of the approach during the evolution of an industrial case study, covering a time span of more than a year.