A Graph Model for RDF
نویسندگان
چکیده
The Resource Description Framework (RDF) is a language for metadata assertions about information resources on the World-Wide Web, and is thus a foundation for a future Semantic Web. The atomic construct of RDF are statements, which are triples consisting of the resource being described, a property, and a property value. A collection of RDF statements can be intuitively understood as a graph: resources are nodes and statements are arcs connecting the nodes. The graph nature of this abstract triple syntax is indeed appealing, but the RDF specification does not distinguish clearly among (1) the term of RDF Graph (merely a set of triples, thus not a standard graph), (2) the mathematical concept of graph, and (3) the graph-like visualization of RDF data (“node and directed-arc diagrams”). This thesis argues that there is need for an explicit graph representation for RDF, which allows the application of technics and results from graph theory and which serves as an intermediate model between the abstract triple syntax and task-specific serialization of RDF data. Directed labeled graphs currently used by default suffer from an ambiguous definition and, furthermore, have limitations inherent in any approach representing RDF triple statements by essentially binary (although labeled) edges. As an alternative, it is natural to consider hypergraphs with ternary edges; from this, we derive RDF bipartite graphs as an intermediate graph-based model for RDF. This proposal is complemented by studies of its transformation cost and its “size” compared to a directed labeled graph representation. The thesis furthermore investigates some issues of RDF’s graph nature in the light of the new model: RDF maps are studied as maps on graphs and an approach to decompose an RDF Graph into data and schema layers is presented. For the processing of RDF data the notions of connectivity and paths in RDF Graphs are essential; because RDF bipartite graphs incorporate statements and properties as nodes into the graph, it turns out that this model conveys a richer sense of connectivity than the standard directed labeled graph representations. Finally, we explore the perspectives of enhancing the expressivity of RDF query languages by a proposal of graph-based query primitives.
منابع مشابه
Roman domination excellent graphs: trees
A Roman dominating function (RDF) on a graph $G = (V, E)$ is a labeling $f : V rightarrow {0, 1, 2}$ suchthat every vertex with label $0$ has a neighbor with label $2$. The weight of $f$ is the value $f(V) = Sigma_{vin V} f(v)$The Roman domination number, $gamma_R(G)$, of $G$ is theminimum weight of an RDF on $G$.An RDF of minimum weight is called a $gamma_R$-function.A graph G is said to be $g...
متن کاملOn trees with equal Roman domination and outer-independent Roman domination numbers
A Roman dominating function (RDF) on a graph $G$ is a function $f : V (G) to {0, 1, 2}$satisfying the condition that every vertex $u$ for which $f(u) = 0$ is adjacent to at least onevertex $v$ for which $f(v) = 2$. A Roman dominating function $f$ is called an outer-independentRoman dominating function (OIRDF) on $G$ if the set ${vin Vmid f(v)=0}$ is independent.The (outer-independent) Roman dom...
متن کاملNeuron Mathematical Model Representation of Neural Tensor Network for RDF Knowledge Base Completion
In this paper, a state-of-the-art neuron mathematical model of neural tensor network (NTN) is proposed to RDF knowledge base completion problem. One of the difficulties with the parameter of the network is that representation of its neuron mathematical model is not possible. For this reason, a new representation of this network is suggested that solves this difficulty. In the representation, th...
متن کاملA Formal Graph Model for RDF and Its Implementation
Formalizing an RDF abstract graph model to be compatible with the RDF formal semantics has remained one of the foundational problems in the Semantic Web. In this paper, we propose a new formal graph model for RDF datasets. This model allows us to express the current model-theoretic semantics in the form of a graph. We also propose the concepts of resource path and triple path as well as an algo...
متن کاملA Framework for Efficient Representative Summarization of RDF Graphs
RDF is the data model of choice for Semantic Web applications. RDF graphs are often large and have heterogeneous, complex structure. Graph summaries are compact structures computed from the input graph; they are typically used to simplify users’ experience and to speed up graph processing. We introduce a formal RDF summarization framework, based on graph quotients and RDF node equivalence; our ...
متن کامل