TBCME: Cannot write to a graph from an SWP

[Tim Smith]

Hi,

I cannot write to an existing graph in the workspace from an SWP.  This is a problem that has plagued me since TBC 5.1.4 so perhaps I'm doing something wrong.  I've attached a minimal example as a project.

The file, swp_write_to_graph.ui.ttlx contains a subclass of ui:Services called w2g:w2graph.  In the ui:prototype, I populate a temp graph (ui:tempGraphFinalOutput) with a single triple.  ui:prototype shown below.

Next, I dump the temp graph to a temporary file using ui:dumpGraph to ensure ui:tempGraphFinalOutput contains the triple.  This works as expected.  Then I try to insert the contents into an RDF file that exists in the workspace.  This file contains nothing but the triples TBC creates when a new RDF file is created.

The SWP call completes successfully but the single triple is not inserted into the existing graph.

The SWP is called using:

http://localhost:8083/tbl/swp?_viewClass=w2g:w2graph&outputGraph=http://example.com/swp_write_to_graph_output&_contextdebug=true

What am I missing such that I cannot insert triples into existing graphs from an SWP?

Note that my ultimate goal is to pass the name of the output graph into the SWP so you will see a constraint setup for that purpose but it is not used in this example.

Any help would be appreciated.  I need to create a number of SWPs and being able to manipulate graphs at will is a skill I need.

Tim

<ui:group let:outputFileGraph="{= IRI(?outputGraph) }">
    <h3>The output graph is {= ?outputGraph }  Graph: {= ?outputFileGraph }</h3>{= smf:trace("Populating the temp graph... ") }<ui:update ui:updateQuery="{!
            INSERT {
                GRAPH ui:tempGraphFinalOutput {
                    ?uri rdfs:label &quot;I am a Thing&quot; .
                } .
            }
            WHERE {
                BIND (spif:buildURI(&quot;&lt;http://example.com/{?1}&gt;&quot;, &quot;i_am_a_thing&quot;) AS ?uri) .
            } }"/>{= smf:trace("Finished!") }

{= smf:trace("Dumping to the debug graph...") }<ui:dumpGraph ui:filePath="/SWP_Example/swp_write_to_graph_debug_output.ttl" ui:graph="ui:tempGraphFinalOutput"/>
    <!-- Try to insert into the output graph -->{= smf:trace("Writing output graph... ") }<ui:setContext ui:queryGraph="ui:tempGraphFinalOutput">
        <ui:update ui:updateQuery="{!
                INSERT {
                    GRAPH &lt;http://example.com/swp_write_to_graph_output&gt; {
                        ?s ?p ?o .
                    } .
                }
                WHERE {
                    ?s ?p ?o .
                } }"/>
    </ui:setContext>
</ui:group>

[Holger Knublauch]

Hi Tim,

you were almost there. The missing info is that ui:update will only write to the context graph when done, not any graph mentioned in the INSERT. So change it to

<ui:setContext ui:queryGraph="&lt;http://example.com/swp_write_to_graph_output&gt;">

        <ui:update ui:updateQuery="{!
                INSERT {

                    ?s ?p ?o .
                }
                WHERE {
                    GRAPH ui:tempGraphFinalOutput {

                        ?s ?p ?o .
                    } .

                } }"/>
    </ui:setContext>

which makes the target graph the active context graph while the source graph is moved into the WHERE clause.

You may also want to wrap the ui:update with a ui:transaction if you want to bundle multiple updates into a single save step. It will otherwise auto-create a transaction for each nested ui:update.

HTH and thanks for taking the time to prepare the bundled example.

Holger

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[Tim Smith]

Hi Holger, 

I was thinking it worked like SPARQL syntax.  Thanks for clearing that up!  Now my SWPs will be much more effective.  :)

Tim

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[Holger Knublauch]

On 18/08/2020 13:41, Tim Smith wrote:

Hi Holger, 

I was thinking it worked like SPARQL syntax. 

It does work like SPARQL, but the ui:update/ui:transaction elements need to decide when to physically write the triples to the file, and that is easier to do if only the context graph is modified. I am sure this could be improved but that's how it works at the moment.

Holger

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[Tim Smith]

That works for me.  It was something I missed in the documentation - although it's clearly written.  I'm just glad to be able to successfully manipulate graphs and move my project forward.  Thanks again!

Tim

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