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RDF and Context (域)

昨天决定把Context翻译成域。今天接着说说用RDF来表示Context,主要是帮我自己理清思路。

去年做了一点这个方向的工作,参加了RDF Next Step Workshop。这是幻灯片:

现在有很多人研究怎么做RDF的时域(Temporal)和空域(Spatial)扩展,文章很多。一部分我认为重要的Temporal RDF的文章待会列到回复里。Spatial RDF我不很熟悉。比如一种建议是这样的:

:stmt2 rdf:subject <s>;
rdf:predicate <p> ;
rdf:object <o> ;
tmp:interval [
tmp:initial “t1″ˆˆxsd:dateTimeStamp ;
tmp:final “t2″ˆˆxsd:dateTimeStamp ] .

也就是用Reification.

Gutierrez等(2007)提出的抽象语法是

s p o [t1 t2]

那如果我们要表示空间域,比如“布什是总统”这句话在2002-2009时间域为真,在美国空间域为真。那我们就要再加一维

s p o [t1 t2] <s>

那如果有更多的其他context呢?比如情绪、上下文、背景数据(比如,“高个子”在NBA和武大饼屋含义不同)。那一个triple上加的注释(annotation)就会越来越多,不胜其烦。

一个办法就是把这些context通通包装起来,放在一个“context document”里面。一个triple,或者一组triple,在某些context里是真的,在其他一些context里为假。在查询的时候,首先指定我们感兴趣的context,则只有相关的triple被返回。

用抽象语法

s p o @c
c  [t1 t2] <s>

看起来差别不大。但是这样有几个好处:

  • 域可以被重用。如果有很多triple共享空间和时间,那不必重复
  • 域可以被推理。一个triple可以属于多个域,或者根据推理的结果属于某个域(域本身可以是变量,在具体语法上是空节点blank-node)
  • 域之间可以有关系。比如我们对谁是总统这种论断制定空域的封闭世界假设,那一旦知道且仅知道“布什是总统”这句话在2002-2009时间域为真,那在2010年“布什是总统”并为假。反之,“今天下雨了”这句话在Boston为真,在NYC可能也为真(开放世界假设)。又,“今天下雨了”这句在曼哈顿为真,这在NYC也为真。

为什么不仅是用Named Graph(名图)?名图只是表示了一种语法上的包含关系。你无法说,或者推理出,(s p o)属于名图g这种关系。名图可以用来做语法上的陈述,但是需要新的语义才能表示context(域)。

未完,下次讲域的不确定性(uncertainty)模态(modal property)。

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  1. 2011/04/06 @ 18:50

    Some temporal modeling related work

    [Allen-1983] Allen, J.: Maintaining knowledge about temporal intervals. Communications of the ACM 26(11), 832-843, 1983

    [Artale-2001] A. Artale, and E. Franconi. A Survey of Temporal Extensions of Description Logics”. Annals of Mathematics and Artificial Intelligence, 30(1-4), 2001.

    [Gutierrez-2007] Gutierrez, C., Hurtado, C., Vaisman, A.: Introducing time into RDF. Transactions on Knowledge Engineering 19(2), 207-218 (2007)

    [Hyvonen-2007] Hyvonen, E.: Modeling and reasoning about changes in ontology time series. Integrated Series in Information Systems 14 II, 319-338 (Jan 2007)

    [Motik-2010] Motik, B.: Representing and querying validity time in RDF and OWL: A logicbased approach. Proceedings of the 9th Internation Semantic Web Conference(ISWC) (2010)

    [Scherp-2009] Ansgar Scherp, Thomas Franz, Carsten Saathoff, and Steffen Staab. 2009. F–a model of events based on the foundational ontology dolce+DnS ultralight. In Proceedings of the fifth international conference on Knowledge capture (K-CAP ’09).

    [Shaw-2009] Ryan Shaw, Raphael Troncy, and Lynda Hardman. 2009. LODE: Linking Open Descriptions of Events. In Proceedings of the 4th Asian Conference on The Semantic Web (ASWC ’09).

    [Straccia-2010] U. Straccia, N. Lopes, G. Lukacsy, and A. Polleres A general framework for representing and reasoning with annotated semantic web data” In Proceedings of the 24th AAAI Conference on Artificial Intelligence (AAAI 2010), Special Track on Artificial Intelligence and the Web, Atlanta, Georgia, USA, July 2010.

    [Tappolet-2009] Tappolet, J., Bernstein, A.: Applied temporal RDF: effcient temporal querying of RDF data with SPARQL. Proceedings of the 6th European Semantic Web Conference (ESWC) 2009

    [Welty-2009] Welty, C., Fikes, R., Makarios, S.: A reusable ontology for fluents in owl. Proceedings of the 4th International Conference on Formal Ontology in Information Systems pp. 226-226, 2006

    [Grandi-2010] T-SPARQL: a TSQL2-like Temporal Query Language for RDF

    [Mateescu-2009] Extending SPARQL with Temporal Logic

    [PerryDissertation-2008] A Framework to Support Spatial, Temporal and Thematic Analytics over Semantic Web Data

  1. 2011/04/08 @ 14:30
  2. 2011/05/28 @ 13:16
  3. 2012/04/16 @ 01:33

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