Rob Vesse created JENA-712:
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Summary: ARQ serialises queries and updates using relative URIs
but does not include a BASE clause
Key: JENA-712
URL: https://issues.apache.org/jira/browse/JENA-712
Project: Apache Jena
Issue Type: Bug
Components: ARQ
Affects Versions: Jena 2.11.2
Reporter: Rob Vesse
Attachments: SparqlRelativeUriTreatment.java
An internal discussion with [~harschware] has raised what we think is a bug in
ARQs behaviour though it is somewhat open to interpretation so may be
controversial.
The code I will attach demonstrates the issue.
The problem arises as follows:
1 - When given a query/update with a relative URI ARQ resolves it against an
implicit Base URI of the current working directory
2 - When applying {{toString()}} on the parsed {{Query}} or {{UpdateRequest}}
the implicit Base URI is used and relative URIs are output but no `BASE` clause
is output
3 - The query is transmitted to a different system which has a different
working directory and so interprets it differently resulting in unexpected
behaviour/errors
This causes us issues because the relative URIs are valid relative to the
working directory of the client but not relative to the working directory of
the server so we want absolute URIs to be transmitted to the server.
For example given the following query string:
{noformat}
SELECT * WHERE { <path/to/thing> a ?type }
{noformat}
Calling {{toString()}} on the resulting {{Query}} object gives the following:
{noformat}
SELECT *
WHERE
{ <path/to/thing> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?type }
{noformat}
Which does not include the `BASE` declaration, if we however force the `Query`
object to have a null base via `setBaseURI((String)null)` ARQ prints the
following when `toString()` is called:
{noformat}
BASE <file:///Users/rvesse/Documents/Work/Code/jena-playground/>
SELECT *
WHERE
{ <path/to/thing> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?type }
{noformat}
More generally it seems that whenever an implicit Base URI is used or where a
Base URI is passed only to the {{QueryFactory.create()}} or
{{UpdateFactory.create()}} call a {{BASE}} declaration is never written i.e.
when there is an {{IRIResolver}} set but not a specific Base URI no {{BASE}}
declaration will be written but URIs will be serialised in relative form.
We can appreciate that other people may have use cases where leaving relative
URIs as-is and not including a `BASE` is desirable but our feeling is that in
the more general case this does more harm than good and lets users shoot
themselves in the foot unwittingly as we have done in this example.
We would like to propose that the default behaviour should be for a `BASE`
declaration to always be written if relative URIs are being output. Or at the
very least we would like the behaviour to be configurable.
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