A Tale of Two Schemas: Creating a Temporal XML Schema from a Snapshot Schema with τXSchema

Abstract

Abstract. The W3C XML Schema recommendation defines the structure and data types for XML documents. XML Schema lacks explicit support for timevarying XML documents. Users have to resort to ad hoc, non-standard mechanisms to create schemas for time-varying XML documents. This paper presents a data model and architecture, called τXSchema, for creating a temporal schema from a non-temporal (snapshot) schema, a temporal annotation, and a physical annotation. The annotations specify which portion(s) of an XML document can vary over time, how the document can change, and where timestamps should be placed. The advantage of using annotations to denote the time-varying aspects is that logical and physical data independence for temporal schemas can be achieved while remaining fully compatible with both existing XML Schema documents and the XML Schema recommendation.

Temporal modelling and management of normative documents in XML format

“…In [11], the authors study the problem of consistently deriving a scheme for managing the temporal counterpart of non-temporal XML documents, starting from the definition of their schema. In particular, they introduce a data model and an architecture, called XSchema, which derives from a non-temporal schema: a temporal schema, a temporal annotation and a physical annotation.…”

“…Such an encoding is enriched with timestamping metatadata complying with an inheritance semantics. The derivation of our XML schema could also be thought as the outcome of a design process similar to the one described in [11], if we started from a snapshot XML schema corresponding to the base structure of a non-temporal (nonversioned) norm text and, then, we augmented it with versioning and timestamping metadata in order to accommodate time-varying data. As to the involved annotation, using the terminology of [11], our XML Schema supports, at each level of the document hierarchy, elements varying over transaction time and valid time, whose lifetime is described as a continuous state, and whose content can change over time.…”

“…On the other hand, our data model also support a temporal element which is not included in the options of the temporal annotation in [11], and we have two different temporal dimensions, validity time and efficacy time, which both have the same semantics as valid time in [11] but need independent management.…”

Weaving temporal and reliability aspects into a schema tapestry

“…Two papers have previously addressed the issue of validating even temporal data [14] [17]. In previous work we developed the XSchema data model and architecture.…”

“…More specifically, we present aspect-oriented XMLSchema (AOXSchema) which is an infrastructure and suite of tools for constructing and validating XML data with embedded metadata. AOXSchema extends XSchema [14][17], adding support for more kinds of metadata than just time. AOXSchema adds aspect-enhanced element types to XML Schema.…”