ObdaFileFormat - ontop/ontop GitHub Wiki
valid for Ontop Version 1
Starting from version 1.7 (build 1599), -ontop- introduces a new format of OBDA text file which users can edit by hand.
An OBDA file in full skeleton:
[PrefixDeclaration]
...
[SourceDeclaration]
...
[MappingDeclaration] @collection [[
...
]]
The detail of the specification is as follows:
This section is the place where users put all the prefix definitions used inside the system.
Keyword header: [PrefixDeclaration]
Each prefix is declared by a pair of its identifier (or name) and its URI definition. For example, to have the default prefix, XSD, OWL and RDF prefixes, the prefix declaration will contain:
[PrefixDeclaration] : http://www.example.org/ontology# xsd: http://www.w3.org/2001/XMLSchema# owl: http://www.w3.org/2002/07/owl# rdf: http://www.w3.org/1999/02/22-rdf-syntax-ns#
Note: there should be no newlines between each entry or the system will fail to read the declarations.
This last section defines the data connection parameters and the mapping assertions. These two declaration sections are considered as one block where each mapping corresponds to the datasource defined at the beginning. Thus, to define different mappings that map to another datasource, users can add another block of source and mapping declaration subsequently and the system will treat them separately.
Data source declaration keyword header: [SourceDeclaration]
This part describes the connection parameters in order to access the database. There are five parameters users have to provide (no newlines should be introduced between each parameter).
For example:
[SourceDeclaration] sourceUri book-connection connectionUrl jdbc:postgresql://example.org/db/book username jsmith password 12345 driverClass org.postgresql.Driver
Mapping declaration keyword header: [MappingDeclaration]
Each mapping is declared by writing its identifier, target and source and separated by a newline for the next mapping.
For example:
[MappingDeclaration] @collection [[
mappingId Book collection
target :BID_{id} a :Book .
source SELECT id FROM books
mappingId Student list
target :{fname}_{lname} a :Student .
source SELECT
fname, lname
FROM
students
...
]]
{|style="border-style: solid;" |Notice that the separator between parameter names and values is TAB instead of SPACE. For example (with whitespace characters visible, i.e., TAB symbol (») and SPACE symbol (•)):
mappingId» collection
target» » :BID_{id} a :Book .
source» » SELECT id FROM books
mappingId» Student list
target» » :{fname}_{lname} a :Student .
source» » SELECT
» » » » •••fname, lname
» » » » FROM
» » » » •••students
Note: There should not be any extra lines at the end of the document before ]]. Otherwise it causes an exception. |}
It is possible to compact more mappings:
mappingId Student list
target :{fname}_{lname} a :Student .
source SELECT fname, lname FROM students
mappingId Student id
target :{fname}_{lname} :hasId {id} .
source SELECT fname, lname, id FROM students
Writing them as:
mappingId Student information
target :{fname}_{lname} a :Student ; :hasId {id} .
source SELECT fname, lname, id FROM students
Note: Remember to add a space before and after semicolumn in the target.