java - 打印日期时间而不在​​ Sparql 输出中指定数据类型

Question

我正在耶拿使用以下 sparql 查询来打印一些信息:

   String qr = "PREFIX : <http://www.example.com/tempsensor#>\n" +
               "PREFIX  xsd: <http://www.w3.org/2001/XMLSchema#> \n"+
                 "SELECT \n"+
                "?Place ?Temperature ?Date \n"+ 
                 "WHERE\n"+
                "{ ?ind :locatedIn ?Place .\n " +
                  "?ind :measures ?Temperature .\n " +
                  "?ind :onDate ?Date .\n " +
                "FILTER(regex(str(?Place),'Delhi', 'i'))\n"+
                "FILTER ( datatype(?Date) = xsd:dateTime)\n"+
                "}";

获得的输出是:

 --------------------------------------------------------------
| Place  | Temperature | Date                                |
==============================================================
| :Delhi | 16          | "2014-10-02T03:20:10"^^xsd:dateTime |

但是，我不希望在日期列中附加数据类型。我需要像这样的输出

--------------------------------------------------------------
| Place  | Temperature | Date                                |
==============================================================
| :Delhi | 16          | 2014-10-02T03:20:10                 |

我应该如何在查询中指定它？

Answer 1

您可以使用项目表达式来获取文字的字符串形式:

String qr = "PREFIX : <http://www.example.com/tempsensor#>\n" +
            "PREFIX  xsd: <http://www.w3.org/2001/XMLSchema#> \n"+
            "SELECT \n"+
            "?Place ?Temperature (STR(?Date) AS ?StrDate) \n"+ 
            "WHERE\n"+
            "{ ?ind :locatedIn ?Place .\n " +
            "  ?ind :measures ?Temperature .\n " +
            "  ?ind :onDate ?Date .\n " +
            "  FILTER(regex(str(?Place),'Delhi', 'i'))\n"+
            "  FILTER ( datatype(?Date) = xsd:dateTime)\n"+
            "}";

这里我们使用内置的STR()函数将 ?Date 的值转换为字符串形式，不带数据类型。

SPARQL 定义了广泛的内置函数，非常值得您花时间阅读 - http://www.w3.org/TR/sparql11-query/#expressions