## A Nested-Graph Model for the Representation and Manipulation of Complex Objects (1994)

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Venue: | ACM Transactions on Information Systems |

Citations: | 36 - 4 self |

### BibTeX

@ARTICLE{Poulovassilis94anested-graph,

author = {Alexandra Poulovassilis and Mark Levene},

title = {A Nested-Graph Model for the Representation and Manipulation of Complex Objects},

journal = {ACM Transactions on Information Systems},

year = {1994},

volume = {12},

pages = {35--68}

}

### Years of Citing Articles

### OpenURL

### Abstract

this paper we report upon a graph-based approach to such an integration. Our use of graphs has two key advantages : firstly, graphs are formally defined, well-understood structures; secondly, it is widely accepted that graph-based formalisms considerably enhance the usability of complex systems [19]. Graphs have been used in conjunction with a number of conventional data models, for example the hierarchical and network models [35], the entity-relationship model [9] and a recent extension thereof for complex objects [27], and various semantic data models [16, 20, 31]. Graphs or hypergraphs [6] have also been used more recently in [12, 17, 23, 25, 33, 36] as a data modelling tool in their own right. We give a comparison between this recent work and our own approach in Section 4 of the paper. Directed graphs have also been the foundation of Hypertext databases [11, 33]. Such databases are graphs consisting of nodes which refer to units of stored information (typically text) and of named links. Each link connects two nodes, the "source" and the "destination". Links are traversed either forwards (from source to destination) or backwards (from destination to source). The process of traversing named links and examining the text associated with nodes is called

### Citations

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Citation Context ...a match for a query, q, with respect to a repository, HR, is NPcomplete. PROOF. We first show NP-Hardness by showing that this problem contains sub-graph isomorphism, which is known to be NP-Complete =-=[15]-=-, as a sub-problem. Let Q be a positive query of the form G = (N+, E+), where the elements of N+ are all variables of the same type, and let there be an equation G = (N, E) in HR. The result follows s... |

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Citation Context ... usability of complex systems [19]. Graphs have been used in conjunction with a number of conventional data models, for example the hierarchical and network models [35], the entity-relationship model =-=[9]-=- and a recent extension thereof for complex objects [27], and various semantic data models [16, 20, 31]. Graphs or hypergraphs [6] have also been used more recently in [12, 17, 23, 25, 33, 36] as a da... |

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Citation Context ... formalisms considerably enhance the usability of complex systems [19]. Graphs have been used in conjunction with a number of conventional data models, for example the hierarchical and network models =-=[35]-=-, the entity-relationship model [9] and a recent extension thereof for complex objects [27], and various semantic data models [16, 20, 31]. Graphs or hypergraphs [6] have also been used more recently ... |

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Citation Context ...a modelling tool in their own right. We give a comparison between this recent work and our own approach in Section 4 of the paper. Directed graphs have also been the foundation of Hypertext databases =-=[11, 33]. Such databases are-=- graphs consisting of nodes which refer to units of stored information (typically text) and of named links. Each link connects two nodes, the "source" and the "destination". Links ... |

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Citation Context ...we are assuming a Herbrand Universe and the Closed World Assumption [29]. This allows us to infer the negation of a node or edge in the absence of a positive match c.f. other non-monotonic formalisms =-=[28]-=-. For example, given a hypernode repository containing the following routes : R1 = ({flight_no,605,airline,AIR1,from,to ... }, {flight_no605, airlineAIR1 ... }) R2 = ({flight_no,301,airline,AIR2,from,... |

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Citation Context ...in all hypernode repositories which are well-typed with respect to TR. We define an update to be a partial recursive mapping from inst(TR) to inst(TR) that is C-generic. Cgenericity was introduced in =-=[21]-=- and intuitively means that, apart from a set of distinguished constants C (which may be the empty set), only the structure of a database is relevant to an update, not the values of the constants in t... |

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