Schema Change Operations for Full Support of Schema Versioning in the τXSchema Framework

Abstract

tXSchema (Currim et al., 2004) is a framework (a language and a suite of tools) for the creation and validation of time-varying XML documents. A tXSchema schema is composed of a conventional XML Schema annotated with physical and logical annotations. All components of a tXSchema schema can evolve over time to reflect changes in the real-world. Since many applications need to keep track of both data and schema evolution, schema versioning has been long advocated to be the best solution to do this. In this paper, we complete the tXSchema framework, which is predisposed from the origin to support schema versioning, with the definition of the operations which are necessary to exploit such feature and make schema versioning functionalities available to final users. Moreover, we propose a new technique for schema versioning in tXSchema, allowing a complete and safe management of schema changes. It supports both versioning of conventional schema and versioning of annotations, in an integrated manner. For each component of a tXSchema schema, our approach provides a complete and sound set of change primitives and a set of high-level change operations, for the maintenance of such a component and defines their operational semantics.

$$\uptau $$ τ OWL: A Systematic Approach to Temporal Versioning of Semantic Web Ontologies

“…These are optional data properties which can be added to a temporal entity. The domain of hasCurrencyValueValidityEndTime or priceTypeValidityEndTime includes the value "now" [5]; the entity that has "now" as the value of its validity end time property represents the current entity until some change occurs.…”

“…τXSchema is a powerful framework (i.e., a data model equipped with a suite of tools) for managing temporal XML documents, well known in the database research community and, in particular, in the field of temporal XML [10]. To complete the framework and extend its functionalities, τXSchema has also been augmented by defining necessary schema change operations [5].…”

High-Level Operations for Creation and Maintenance of Temporal and Conventional Schema in the tauXSchema Framework

“…In our previous work, we proposed three complete and sound sets of low-level operations, for changing conventional schema [14,15], logical and physical annotations [11,12], and temporal schema [16]. Obviously, these operations are not designated to be used directly by IJXSchema designers, since they are too primitive and not very user-friendly.…”

“…Hence, a transaction consists of a sequence of valid schema change operations to be carried out on the IJXSchema framework that would be either all successfully completed or all cancelled. The proposed high-level operations are based on the low-level operations (i.e., primitives) already defined in [11,12], [14,15], and [16]. Since each low-level operation is consistency preserving (i.e., each operation applied to a consistent IJXSchema schema component produces a consistent IJXSchema schema component) and each high-level operation is defined using a sequence of low-level operations, the proposed high-level operations are consequently consistency preserving.…”

“…Indeed, we propose three sets of highlevel operations for changing temporal schema, conventional schema, and annotations. These high-level operations are based on the low-level operations proposed in our previous work [11,12,14,15,16]. They are also consistency preserving and more user-friendly than the low-level operations.…”