Temporal JSON Web services are the primary suppliers of data on the web, such data is typically formatted using JavaScript Object Notation (JSON) and only the current JSON snapshot is available from a service. But data evolves over time as it is added to, modified, or reduced. Providing an historical view of data is important in many applications. This paper describes how to capture the evolving history of a JSON document and how to support temporal queries. Our approach is to model temporal JSON as a virtual document in which time metadata is mixed with JSON data. The time metadata records when the JSON data is alive. We also describe how to navigate to data within the virtual document. The primary technical contribution of the paper is to show how to represent the virtual model in JSON and how to map temporal path expressions to the representational model. Experiments show that our model is efficient.

Algebraic Operations on Spatiotemporal Data Based on RDF In the context of the Semantic Web, the Resource Description Framework (RDF), a language proposed by W3C, has been used for conceptual description, data modeling, and data querying. The algebraic approach has been proven to be an effective way to process queries, and algebraic operations in RDF have been investigated extensively. However, the study of spatiotemporal RDF algebra has just started and still needs further attention. This paper aims to explore an algebraic operational framework to represent the content of spatiotemporal data and support RDF graphs. To accomplish our study, we defined a spatiotemporal data model based on RDF. On this basis, the spatiotemporal semantics and the spatiotemporal algebraic operations were investigated. We defined five types of graph algebras, and, in particular, the filter operation can filter the spatiotemporal graphs using a graph pattern. Besides this, we put forward a spatiotemporal RDF syntax specification to help users browse, query, and reason with spatiotemporal RDF graphs. The syntax specification illustrates the filter rules, which contribute to capturing the spatiotemporal RDF semantics and provide a number of advanced functions for building data queries.