A Survey on Models and Query Languages for Temporally Annotated RDF
---
paper_title: Annotated RDF

paper_content:

Real-world use of RDF requires the ability to transparently represent and explain metadata associated with RDF triples. For example, when RDF triples are extracted automatically by information extraction programs, there is a need to represent where the triples came from, what their temporal validity is, and how certain we are that the triple is correct. Today, there is no theoretically clean and practically scalable mechanism that spans these different needs - reification is the only solution propose to date, and its implementations have been ugly. In this paper, we present Annotated RDF (or aRDF for short) in which RDF triples are annotated by members of a partially ordered set (with bottom element) that can be selected in any way desired by the user. We present a formal declarative semantics (model theory) for annotated RDF and develop algorithms to check consistency of aRDF theories and to answer queries to aRDF theories. We show that annotated RDF supports users who need to think about the uncertainty, temporal aspects, and provenance of the RDF triples in an RDF database. We develop a prototype aRDF implementation and show that our algorithms work efficiently even on real world data sets containing over 10 million triples.
---
paper_title: Semantic Management of Streaming Data

paper_content:

One of the fundamental challenges facing the unprecedented data deluge produced by the sensor networks is how to manage time-series streaming data so that they can be reasoning-ready and provenance-aware. Semantic web technology shows great promise but lacks adequate support for the notion of time. We present a system for the representation, indexing and querying of time-series data, especially streaming data, using the semantic web approach. This system incorporates a special RDF vocabulary and a semantic interpretation for time relationships. The resulting framework, which we refer to as Time-Annotated RDF, provides basic functionality for the representation and querying of time-related data. The capabilities of Time-Annotated RDF were implemented as a suite of Java APIs on top of Tupelo, a semantic content management middleware, to provide transparent integration among heterogeneous data, as present in streams and other data sources, and their metadata. We show how this system supports commonly used time-related queries using Time-Annotated SPARQL introduced in this paper as well as an analysis of the TA-RDF data model. Such prototype system has already seen successful usage in a virtual sensor project where near-real-time radar data streams need to be fetched, indexed, processed and re-published as new virtual sensor streams.
---
paper_title: Named graphs

paper_content:

The Semantic Web consists of many RDF graphs nameable by URIs. This paper extends the syntax and semantics of RDF to cover such named graphs. This enables RDF statements that describe graphs, which is beneficial in many Semantic Web application areas. Named graphs are given an abstract syntax, a formal semantics, an XML syntax, and a syntax based on N3. SPARQL is a query language applicable to named graphs. A specific application area discussed in detail is that of describing provenance information. This paper provides a formally defined framework suited to being a foundation for the Semantic Web trust layer.
---
paper_title: T-SPARQL: A TSQL2-like Temporal Query Language for RDF

paper_content:

In this paper, we present a temporal extension of the SPARQL query language for RDF graphs. The new language is based on a temporal RDF database model employing triple timestamping with temporal elements, which best preserves the scalability property enjoyed by triple storage technologies, especially in a multi-temporal setting. The proposed SPARQL extensions are aimed at embedding several features of the TSQL2 consensual language designed for temporal relational databases.
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paper_title: nSPARQL: A navigational language for RDF

paper_content:

Navigational features have been largely recognized as fundamental for graph database query languages. This fact has motivated several authors to propose RDF query languages with navigational capabilities. In particular, we have argued in a previous paper that nested regular expressions are appropriate to navigate RDF data, and we have proposed the nSPARQL query language for RDF, that uses nested regular expressions as building blocks. In this paper, we study some of the fundamental properties of nSPARQL concerning expressiveness and complexity of evaluation. Regarding expressiveness, we show that nSPARQL is expressive enough to answer queries considering the semantics of the RDFS vocabulary by directly traversing the input graph. We also show that nesting is necessary to obtain this last result, and we study the expressiveness of the combination of nested regular expressions and SPARQL operators. Regarding complexity of evaluation, we prove that the evaluation of a nested regular expression E over an RDF graph G can be computed in time O (|G |·|E |).
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paper_title: On Modeling and Querying Concept Evolution

paper_content:

Entities and the concepts they instantiate evolve over time. For example, a corporate entity may have resulted from a series of mergers and splits, or a concept such as that of Whale may have evolved along with our understanding of the physical world. We propose a model for capturing and querying concept evolution. Our proposal extends an RDF-like model with temporal features and evolution operators. In addition, we provide a query language that exploits these extensions and supports historical queries. Moreover, we study how evolution information can be exploited to answer queries that are agnostic to evolution details (hence, evolution-unaware). For these, we propose dynamic programming algorithms and evaluate their efficiency and scalability by experimenting with both real and synthetic datasets.
---
paper_title: Introducing Time into RDF

paper_content:

The resource description framework (RDF) is a metadata model and language recommended by the W3C. This paper presents a framework to incorporate temporal reasoning into RDF, yielding temporal RDF graphs. We present a semantics for these kinds of graphs which includes the notion of temporal entailment and a syntax to incorporate this framework into standard RDF graphs, using the RDF vocabulary plus temporal labels. We give a characterization of temporal entailment in terms of RDF entailment and show that the former does not yield extra asymptotic complexity with respect to nontemporal RDF graphs. We also discuss temporal RDF graphs with anonymous timestamps, providing a theoretical framework for the study of temporal anonymity. Finally, we sketch a temporal query language for RDF, along with complexity results for query evaluation that show that the time dimension preserves the tractability of answers
---
paper_title: Annotated RDF

paper_content:

Real-world use of RDF requires the ability to transparently represent and explain metadata associated with RDF triples. For example, when RDF triples are extracted automatically by information extraction programs, there is a need to represent where the triples came from, what their temporal validity is, and how certain we are that the triple is correct. Today, there is no theoretically clean and practically scalable mechanism that spans these different needs - reification is the only solution propose to date, and its implementations have been ugly. In this paper, we present Annotated RDF (or aRDF for short) in which RDF triples are annotated by members of a partially ordered set (with bottom element) that can be selected in any way desired by the user. We present a formal declarative semantics (model theory) for annotated RDF and develop algorithms to check consistency of aRDF theories and to answer queries to aRDF theories. We show that annotated RDF supports users who need to think about the uncertainty, temporal aspects, and provenance of the RDF triples in an RDF database. We develop a prototype aRDF implementation and show that our algorithms work efficiently even on real world data sets containing over 10 million triples.
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paper_title: Completeness, decidability and complexity of entailment for RDF Schema and a semantic extension involving the OWL vocabulary

paper_content:

We prove that entailment for RDF Schema (RDFS) is decidable, NP-complete, and in P if the target graph does not contain blank nodes. We show that the standard set of entailment rules for RDFS is incomplete and that this can be corrected by allowing blank nodes in predicate position. We define semantic extensions of RDFS that involve datatypes and a subset of the OWL vocabulary that includes the property-related vocabulary (e.g. FunctionalProperty), the comparisons (e.g. sameAs and differentFrom) and the value restrictions (e.g. allValuesFrom). These semantic extensions are in line with the 'if-semantics' of RDFS and weaker than the 'iff-semantics' of D-entailment and OWL (DL or Full). For these semantic extensions we present entailment rules, prove completeness results, prove that consistency is in P and that, just as for RDFS, entailment is NP-complete, and in P if the target graph does not contain blank nodes. There are no restrictions on use to obtain decidability: classes can be used as instances.
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paper_title: Supporting Complex Thematic, Spatial and Temporal Queries over Semantic Web Data

paper_content:

Spatial and temporal data are critical components in many applications. This is especially true in analytical domains such as national security and criminal investigation. Often, the analytical process requires uncovering and analyzing complex thematic relationships between disparate people, places and events. Fundamentally new query operators based on the graph structure of Semantic Web data models, such as semantic associations, are proving useful for this purpose. However, these analysis mechanisms are primarily intended for thematic relationships. In this paper, we describe a framework built around the RDF metadata model for analysis of thematic, spatial and temporal relationships between named entities. We discuss modeling issues and present a set of semantic query operators. We also describe an efficient implementation in Oracle DBMS and demonstrate the scalability of our approach with a performance study using a large synthetic dataset from the national security domain.
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paper_title: Combining uncertainty and description logic rule-based reasoning in situation-aware robots

paper_content:

The paper addresses how a robot can maintain a state representation of all that it knows about the environment over time and space, given its observations and its domain knowledge. The advantage in combining domain knowledge and observations is that the robot can in this way project from the past into the future, and reason from observations to more general statements to help guide how it plans to act and interact. The difficulty lies in the fact that observations are typically uncertain and logical inference for completion against a knowledge base is computationally hard.
---
paper_title: Introducing Time into RDF

paper_content:

The resource description framework (RDF) is a metadata model and language recommended by the W3C. This paper presents a framework to incorporate temporal reasoning into RDF, yielding temporal RDF graphs. We present a semantics for these kinds of graphs which includes the notion of temporal entailment and a syntax to incorporate this framework into standard RDF graphs, using the RDF vocabulary plus temporal labels. We give a characterization of temporal entailment in terms of RDF entailment and show that the former does not yield extra asymptotic complexity with respect to nontemporal RDF graphs. We also discuss temporal RDF graphs with anonymous timestamps, providing a theoretical framework for the study of temporal anonymity. Finally, we sketch a temporal query language for RDF, along with complexity results for query evaluation that show that the time dimension preserves the tractability of answers
---
paper_title: A General Framework for Representing, Reasoning and Querying with Annotated Semantic Web Data

paper_content:

We describe a generic framework for representing and reasoning with annotated Semantic Web data, a task becoming more important with the recent increased amount of inconsistent and non-reliable meta-data on the web. We formalise the annotated language, the corresponding deductive system and address the query answering problem. Previous contributions on specific RDF annotation domains are encompassed by our unified reasoning formalism as we show by instantiating it on (i) temporal, (ii) fuzzy, and (iii) provenance annotations. Moreover, we provide a generic method for combining multiple annotation domains allowing to represent, e.g. temporally-annotated fuzzy RDF. Furthermore, we address the development of a query language -- AnQL -- that is inspired by SPARQL, including several features of SPARQL 1.1 (subqueries, aggregates, assignment, solution modifiers) along with the formal definitions of their semantics.
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paper_title: Minimal Deductive Systems for RDF

paper_content:

This paper presents a minimalist program for RDF, by showing how one can do without several predicates and keywords of the RDF Schema vocabulary, obtaining a simpler language which preserves the original semantics. This approach is beneficial in at least two directions: (a) To have a simple abstract fragment of RDFS easy to formalize and to reason about, which captures the essence of RDFS; (b) To obtain algorithmic properties of deduction and optimizations that are relevant for particular fragments. Among our results are: the identification of a simple fragment of RDFS; the proof that it encompasses the main features of RDFS; a formal semantics and a deductive system for it; sound and complete deductive systems for their sub-fragments; and an ${\cal O}(n \log n)$ complexity bound for ground entailment in this fragment.
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paper_title: A temporal extension of the Hayes and ter Horst entailment rules for RDFS and OWL

paper_content:

Temporal encoding schemes using RDF and OWL are often plagued by a massive proliferation of useless “container” objects. Reasoning and querying with such representations is extremely complex, expensive, and error-prone. We present a temporal extension of the Hayes and ter Horst entailment rules for RDFS/OWL. The extension is realized by extending RDF triples with further temporal arguments and requires only some lightweight forms of reasoning. The approach has been implemented in the forward chaining engine HFC.
---
paper_title: Semantic Management of Streaming Data

paper_content:

One of the fundamental challenges facing the unprecedented data deluge produced by the sensor networks is how to manage time-series streaming data so that they can be reasoning-ready and provenance-aware. Semantic web technology shows great promise but lacks adequate support for the notion of time. We present a system for the representation, indexing and querying of time-series data, especially streaming data, using the semantic web approach. This system incorporates a special RDF vocabulary and a semantic interpretation for time relationships. The resulting framework, which we refer to as Time-Annotated RDF, provides basic functionality for the representation and querying of time-related data. The capabilities of Time-Annotated RDF were implemented as a suite of Java APIs on top of Tupelo, a semantic content management middleware, to provide transparent integration among heterogeneous data, as present in streams and other data sources, and their metadata. We show how this system supports commonly used time-related queries using Time-Annotated SPARQL introduced in this paper as well as an analysis of the TA-RDF data model. Such prototype system has already seen successful usage in a virtual sensor project where near-real-time radar data streams need to be fetched, indexed, processed and re-published as new virtual sensor streams.
---
paper_title: A Semantic Web Primer

paper_content:

The development of the Semantic Web, with machine-readable content, has the potential to revolutionize the World Wide Web and its uses. A Semantic Web Primer provides an introduction and guide to this continuously evolving field, describing its key ideas, languages, and technologies. Suitable for use as a textbook or for independent study by professionals, it concentrates on undergraduate-level fundamental concepts and techniques that will enable readers to proceed with building applications on their own and includes exercises, project descriptions, and annotated references to relevant online materials.The third edition of this widely used text has been thoroughly updated, with significant new material that reflects a rapidly developing field. Treatment of the different languages (OWL2, rules) expands the coverage of RDF and OWL, defining the data model independently of XML and including coverage of N3/Turtle and RDFa. A chapter is devoted to OWL2, the new W3C standard. This edition also features additional coverage of the query language SPARQL, the rule language RIF and the possibility of interaction between rules and ontology languages and applications. The chapter on Semantic Web applications reflects the rapid developments of the past few years. A new chapter offers ideas for term projects. Additional material, including updates on the technological trends and research directions, can be found at http://www.semanticwebprimer.org.
---
paper_title: On Modeling and Querying Concept Evolution

paper_content:

Entities and the concepts they instantiate evolve over time. For example, a corporate entity may have resulted from a series of mergers and splits, or a concept such as that of Whale may have evolved along with our understanding of the physical world. We propose a model for capturing and querying concept evolution. Our proposal extends an RDF-like model with temporal features and evolution operators. In addition, we provide a query language that exploits these extensions and supports historical queries. Moreover, we study how evolution information can be exploited to answer queries that are agnostic to evolution details (hence, evolution-unaware). For these, we propose dynamic programming algorithms and evaluate their efficiency and scalability by experimenting with both real and synthetic datasets.
---
paper_title: Named graphs

paper_content:

The Semantic Web consists of many RDF graphs nameable by URIs. This paper extends the syntax and semantics of RDF to cover such named graphs. This enables RDF statements that describe graphs, which is beneficial in many Semantic Web application areas. Named graphs are given an abstract syntax, a formal semantics, an XML syntax, and a syntax based on N3. SPARQL is a query language applicable to named graphs. A specific application area discussed in detail is that of describing provenance information. This paper provides a formally defined framework suited to being a foundation for the Semantic Web trust layer.
---
paper_title: SPARQL-ST: Extending SPARQL to Support Spatiotemporal Queries

paper_content:

Spatial and temporal data is plentiful on the Web, and Semantic Web technologies have the potential to make this data more accessible and more useful. Semantic Web researchers have consequently made progress towards better handling of spatial and temporal data.SPARQL, the W3C-recommended query language for RDF, does not adequately support complex spatial and temporal queries. In this work, we present the SPARQL-ST query language. SPARQL-ST is an extension of SPARQL for complex spatiotemporal queries. We present a formal syntax and semantics for SPARQL-ST. In addition, we describe a prototype implementation of SPARQL-ST and demonstrate the scalability of this implementation with a performance study using large real-world and synthetic RDF datasets.
---
paper_title: Maintaining knowledge about temporal intervals

paper_content:

An interval-based temporal logic is introduced, together with a computationally effective reasoning algorithm based on constraint propagation. This system is notable in offering a delicate balance between
---
paper_title: Annotated RDF

paper_content:

Real-world use of RDF requires the ability to transparently represent and explain metadata associated with RDF triples. For example, when RDF triples are extracted automatically by information extraction programs, there is a need to represent where the triples came from, what their temporal validity is, and how certain we are that the triple is correct. Today, there is no theoretically clean and practically scalable mechanism that spans these different needs - reification is the only solution propose to date, and its implementations have been ugly. In this paper, we present Annotated RDF (or aRDF for short) in which RDF triples are annotated by members of a partially ordered set (with bottom element) that can be selected in any way desired by the user. We present a formal declarative semantics (model theory) for annotated RDF and develop algorithms to check consistency of aRDF theories and to answer queries to aRDF theories. We show that annotated RDF supports users who need to think about the uncertainty, temporal aspects, and provenance of the RDF triples in an RDF database. We develop a prototype aRDF implementation and show that our algorithms work efficiently even on real world data sets containing over 10 million triples.
---
paper_title: T-SPARQL: A TSQL2-like Temporal Query Language for RDF

paper_content:

In this paper, we present a temporal extension of the SPARQL query language for RDF graphs. The new language is based on a temporal RDF database model employing triple timestamping with temporal elements, which best preserves the scalability property enjoyed by triple storage technologies, especially in a multi-temporal setting. The proposed SPARQL extensions are aimed at embedding several features of the TSQL2 consensual language designed for temporal relational databases.
---
paper_title: Introducing Time into RDF

paper_content:

The resource description framework (RDF) is a metadata model and language recommended by the W3C. This paper presents a framework to incorporate temporal reasoning into RDF, yielding temporal RDF graphs. We present a semantics for these kinds of graphs which includes the notion of temporal entailment and a syntax to incorporate this framework into standard RDF graphs, using the RDF vocabulary plus temporal labels. We give a characterization of temporal entailment in terms of RDF entailment and show that the former does not yield extra asymptotic complexity with respect to nontemporal RDF graphs. We also discuss temporal RDF graphs with anonymous timestamps, providing a theoretical framework for the study of temporal anonymity. Finally, we sketch a temporal query language for RDF, along with complexity results for query evaluation that show that the time dimension preserves the tractability of answers
---
paper_title: A General Framework for Representing, Reasoning and Querying with Annotated Semantic Web Data

paper_content:

We describe a generic framework for representing and reasoning with annotated Semantic Web data, a task becoming more important with the recent increased amount of inconsistent and non-reliable meta-data on the web. We formalise the annotated language, the corresponding deductive system and address the query answering problem. Previous contributions on specific RDF annotation domains are encompassed by our unified reasoning formalism as we show by instantiating it on (i) temporal, (ii) fuzzy, and (iii) provenance annotations. Moreover, we provide a generic method for combining multiple annotation domains allowing to represent, e.g. temporally-annotated fuzzy RDF. Furthermore, we address the development of a query language -- AnQL -- that is inspired by SPARQL, including several features of SPARQL 1.1 (subqueries, aggregates, assignment, solution modifiers) along with the formal definitions of their semantics.
---
paper_title: Representing and Querying Validity Time in RDF and OWL: A Logic-based Approach

paper_content:

RDF(S) and OWL 2 can currently represent only static information. In practice, however, the truth of statements often changes with time. Semantic Web applications often need to represent such changes and reason about them. In this paper we present a logic-based approach for representing validity time in RDF(S) and OWL 2. Unlike the existing proposals, our approach is applicable to nondeterministic entailment relations and/or entailment relations that involve existential quantification, such as the OWL 2 Direct Entailment and the OWL 2 RDF-Based Entailment. We also present an extension of SPARQL that can be used to query temporal RDF(S) and OWL 2. Moreover, we present a general query evaluation algorithm that can be used with all entailment relations used in the Semantic Web. Finally, we present two optimizations of the algorithm that are applicable to entailment relations characterized by a set of deterministic rules, such RDF(S) and OWL 2 RL/RDF Entailment.
---
paper_title: SPARQL-ST: Extending SPARQL to Support Spatiotemporal Queries

paper_content:

Spatial and temporal data is plentiful on the Web, and Semantic Web technologies have the potential to make this data more accessible and more useful. Semantic Web researchers have consequently made progress towards better handling of spatial and temporal data.SPARQL, the W3C-recommended query language for RDF, does not adequately support complex spatial and temporal queries. In this work, we present the SPARQL-ST query language. SPARQL-ST is an extension of SPARQL for complex spatiotemporal queries. We present a formal syntax and semantics for SPARQL-ST. In addition, we describe a prototype implementation of SPARQL-ST and demonstrate the scalability of this implementation with a performance study using large real-world and synthetic RDF datasets.
---

Title: A Survey on Models and Query Languages for Temporally Annotated RDF

Section 1: INTRODUCTION
Description 1: This section provides an overview of RDF, its static nature, and the need for temporally annotated RDF, introducing the main focus of the paper.

Section 2: WORKS THAT HAVE THEIR OWN MODEL THEORY
Description 2: This section reviews models and approaches that have developed their own theoretical framework for temporally annotated RDF.

Section 3: WORKS THAT EXTEND RDF SIMPLE ENTAILMENT
Description 3: This section discusses works that extend the simple entailment of RDF to support temporal annotations, further dividing into direct and indirect translations to RDF.

Section 4: APPROACHES THAT TRANSLATE TO RDF
Description 4: This section examines specific methods that utilize named graphs and other techniques to translate temporally annotated RDF into standard RDF for querying.

Section 5: OTHER APPROACHES
Description 5: This section delves into additional approaches with unique models, including multi-dimensional time domains, uncertain temporal knowledge bases, and evolution-aware querying.

Section 6: WORKS THAT EXTEND RDFS ENTAILMENT
Description 6: This section covers extensions of RDFS entailment to handle temporally annotated RDF, detailing methods and their theoretical implications.

Section 7: CONCLUSION-DISCUSSION
Description 7: This section summarizes the reviewed models and query languages, comparing their capabilities and performance, and discusses potential future research directions.