|
以文本方式查看主题 - 计算机科学论坛 (http://bbs.xml.org.cn/index.asp) -- 『 Semantic Web(语义Web)/描述逻辑/本体 』 (http://bbs.xml.org.cn/list.asp?boardid=2) ---- Jena推理介绍中的两段英文描述，各位大拿帮忙看看具体是什么意思 (http://bbs.xml.org.cn/dispbbs.asp?boardid=2&rootid=&id=37201) |
|
-- 作者：wumingrock -- 发布时间：8/25/2006 3:15:00 PM -- Jena推理介绍中的两段英文描述，各位大拿帮忙看看具体是什么意思 The default API supports accessing all entailed information at the level of individual triples. This is surprisingly flexible but there are queries which cannot be easily supported this way. The first such is when the query needs to make reference to an expression which is not already present in the data. For example, in description logic systems it is often possible to ask if there are any instances of some class expression. Whereas using the triple-based approach we can only ask if there are any instances of some class already defined (though it could be defined by a bNode rather than be explicitly named). To overcome this limitation the InfModel API supports a notion of "posit", that is a set of assertions which can be used to temporarily declare new information such as the definition of some class expression. These temporary assertions can then be referenced by the other arguments to the listStatements command. With the current reasoners this is an expensive operation, involving the temporary creation of an entire new model with the additional posits added and all inference has to start again from scratch. Thus it is worth considering preloading your data with expressions you might need to query over. However, for some external reasoners, especially description logic reasoners, we anticipate restricted uses of this form of listStatement will be important. |
|
-- 作者：wumingrock -- 发布时间：8/25/2006 3:17:00 PM -- 看了好久，还是不太明白这两段话的确切意思，拜托各位帮帮小弟了！！ |
|
-- 作者：jpz6311whu -- 发布时间：8/25/2006 3:29:00 PM -- 主要是讲jena中InfModel的实现机制，也就是a notion of "posit"这种方法，它能克服第一段所说的局限性，但是目前实现效率比较低，所以要restricted uses of this form of listStatement |
|
-- 作者：wumingrock -- 发布时间：8/25/2006 4:44:00 PM -- 楼上的大哥，你讲的这些太high level了吧。。。。能不能具体些。。。 我就没搞清楚，描述逻辑系统和基于三元组的方法不同之处在哪里。。。 |
|
W 3 C h i n a ( since 2003 ) 旗 下 站 点 苏ICP备05006046号《全国人大常委会关于维护互联网安全的决定》《计算机信息网络国际联网安全保护管理办法》 |
46.875ms |