使用另一个表的值进行R2RML映射

Question

我想使用R2RML和Virtuoso从MySql源映射一些表。我有一个带有"Things“的表，我希望它们有一个谓词，这些谓词不是URI，而是来自名称列的谓词，来自通过thingID连接的表”值“。我可以通过"Thing“的ID将表”值“映射到”thingId“的”值“--但是通过这种映射，我只能得到相应”值“条目的URI。我想要的是存储在列"Value“中的字符串。

例如，预期结果的三倍应该是：

<http://localhost:8890/ex/things/1> rdf:type <http://localhost:8890/ex/types/vmware> ;
ex:hasValue "Name from the table Values" .

Example of Things table: 
ID  typeId 
1   3

Example of the Types table: 
ID   Name 
3    vmware

值表的示例：

ID   thingId   Value 
1    1         VMware Virtual Platform

到目前为止，这是我的地图：

<#TriplesMapThings> a rr:TriplesMap; rr:logicalTable [ rr:tableSchema "exdb" ; rr:tableOwner "ex" ; rr:tableName "Things" ]; 
rr:subjectMap [ rr:termType rr:IRI  ; rr:template "http://localhost:8890/ex/things/{id}"; rr:class ex:Things; rr:graph <http://localhost:8890/ex_test#> ];
rr:predicateObjectMap [ rr:predicateMap [ rr:constant ex:id ] ; rr:objectMap [ rr:column "id" ]; ] ;
rr:predicateObjectMap [ rr:predicateMap [ rr:constant ex:typeid ] ; rr:objectMap [ rr:column "typeId" ]; ] ;

rr:predicateObjectMap [ rr:predicateMap [ rr:constant rdf:type ] ; rr:objectMap [ rr:parentTriplesMap <#TriplesMapTypes>; rr:joinCondition [rr:child "typeId"; rr:parent "id";]; ];] ;

rr:predicateObjectMap [ rr:predicateMap [ rr:constant ex:hasValue ] ; rr:objectMap [ rr:parentTriplesMap <#TriplesMapValues>; rr:joinCondition [rr:child "id"; rr:parent "thingId";]; ];] .





<#TriplesMapTypes> a rr:TriplesMap; rr:logicalTable [ rr:tableSchema "exdb" ; rr:tableOwner "ex" ; rr:tableName "Types" ]; 
rr:subjectMap [ rr:termType rr:IRI  ; rr:template "http://localhost:8890/ex/types/{nameUri}"; rr:class owl:Class; rr:graph <http://localhost:8890/ex_test#> ];
rr:predicateObjectMap [ rr:predicateMap [ rr:constant ex:id ] ; rr:objectMap [ rr:column "id" ]; ] ;
rr:predicateObjectMap [ rr:predicateMap [ rr:constant ex:name ] ; rr:objectMap [ rr:column "name" ]; ] .





<#TriplesMapValues> a rr:TriplesMap; rr:logicalTable [ rr:tableSchema "exdb" ; rr:tableOwner "ex" ; rr:tableName "Values" ]; 
rr:subjectMap [ rr:termType rr:IRI  ; rr:template "http://localhost:8890/ex/values/{id}"; rr:class ex:Values; rr:graph <http://localhost:8890/ex_test#> ];

rr:predicateObjectMap [ rr:predicateMap [ rr:constant rdf:type ] ; rr:objectMap [ rr:parentTriplesMap <#TriplesMapAttributes>; rr:joinCondition [rr:child "attributeId"; rr:parent "id";]; ];]  ;

rr:predicateObjectMap [ rr:predicateMap [ rr:constant ex:hasThing ] ; rr:objectMap [ rr:parentTriplesMap <#TriplesMapThings>; rr:joinCondition [rr:child "thingId"; rr:parent "id";]; ];]  ;

rr:predicateObjectMap [ rr:predicateMap [ rr:constant ex:id ] ; rr:objectMap [ rr:column "id" ]; ] ;
rr:predicateObjectMap [ rr:predicateMap [ rr:constant ex:thingid ] ; rr:objectMap [ rr:column "thingId" ]; ] ;
rr:predicateObjectMap [ rr:predicateMap [ rr:constant ex:value ] ; rr:objectMap [ rr:column "value" ]; ] .

Answer 1

最简单的方法是使用SQL查询：

<#TriplesMapThings> a rr:TriplesMap;
rr:logicalTable [rr:sqlQuery “SELECT Things.ID, Types.Name FROM Things, Types WHERE Things.typeId = Types.ID” ];
rr:subjectMap [ rr:template “http://localhost:8890/ex/things/{ID}”];
rr:predicateObjectMap [
    rr:predicate rdf:type;
    rr:objectMap [ rr:template “http://localhost:8890/ex/types/{Name}”]
].
<#TriplesMapValues> a rr:TriplesMap;
rr:logicalTable [rr:tableName “Values” ];
rr:subjectMap [ rr:template “http://localhost:8890/ex/things/{thingId}”];
rr:predicateObjectMap [
    rr:predicate ex:hasValue;
    rr:objectMap [ rr:column “Value”]
].

然而，这看起来不适用于Virtuoso。根据他们的文档， is not supported。

如果Types.Name是唯一的密钥，我相信您可以执行以下操作：

<#TriplesMapThings> a rr:TriplesMap;
rr:logicalTable [rr:tableName “Things” ];
rr:subjectMap [ rr:template “http://localhost:8890/ex/things/{ID}”];
rr:predicateObjectMap [
    rr:predicate rdf:type;
    rr:objectMap [ 
        rr:parentTriplesMap <#TriplesMapTypes>;
        rr:joinCondition [ rr:child “typeId”; rr:parent “ID”];
    ]
].

<#TriplesMapTypes> a rr:TriplesMap;
rr:logicalTable [rr:tableName “Types” ];
rr:subjectMap [ rr:template “http://localhost:8890/ex/types/{Name}”].

<#TriplesMapValues> a rr:TriplesMap;
rr:logicalTable [rr:tableName “Values” ];
rr:subjectMap [ rr:template “http://localhost:8890/ex/things/{thingId}”];
rr:predicateObjectMap [
    rr:predicate ex:hasValue;
    rr:objectMap [ rr:column “Value”]
].

注意，您正在使用Types属性为表Name定义主题URI。因此，即使在Things.typeId和Types.ID之间加入，R2RML处理器也应该使用<#TriplesMapTypes> TriplesMap的主题定义。

如果Types.Name不是唯一的键，那么您必须使用SQL查询来完成它。

请注意，R2RML的设计是为了在需要复杂映射(就像您试图执行的映射)时使用SQL查询。