Difference between revisions of "Virtual Graphs"
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Virtual graphs are manipulated via the following interfaces | Virtual graphs are manipulated via the following interfaces | ||
− | * org.simantics.db.service.VirtualGraphSupport, for management | + | * '''org.simantics.db.service.VirtualGraphSupport''', for management |
− | * org.simantics.db.request.WriteTraits, for identifying the graph to write into | + | * '''org.simantics.db.request.WriteTraits''', for identifying the graph to write into |
== Specification == | == Specification == |
Revision as of 22:04, 3 September 2011
Intro
The Simantics database client allows for defining memory-based and disk-based graph fragments which are applied on top of the server-based semantic graph.
A reading user perceives the combined model and the virtual graph information can be specifically queried if necessary.
A modifying user needs to specify in which virtual graph the modifications are made.
Virtual graphs are manipulated via the following interfaces
- org.simantics.db.service.VirtualGraphSupport, for management
- org.simantics.db.request.WriteTraits, for identifying the graph to write into
Specification
A write request has a single graph into which it writes. This is determined by WriteTraits and usually as a parameter to WriteRequest. If null is provided, the client applies modifications into the persistent graph. The following rules apply
- New resources are created into the given virtual graph
- Claim statements are added into the given virtual graph
- Value changes are applied into the given virtual graph
- For denied statements the location of the statement is determined and the statement is removed from that virtual graph.
The user can perform modifications into multiple virtual graphs within a single transaction. This is accomplished by issuing a new synchronous modification (WriteGraph.sync) into a new virtual graph.
Examples
The following code examples show in practice how to write into virtual graphs, both memory- and disk-based. Writing to several virtual graphs within the same write transaction is also demonstrated.
<syntaxhighlight lang="java"> package org.simantics.db.tests.api.support.virtualGraphSupport;
import org.simantics.db.ReadGraph; import org.simantics.db.RequestProcessor; import org.simantics.db.Resource; import org.simantics.db.Session; import org.simantics.db.Statement; import org.simantics.db.VirtualGraph; import org.simantics.db.WriteGraph; import org.simantics.db.common.request.ReadRequest; import org.simantics.db.common.request.WriteRequest; import org.simantics.db.common.request.WriteResultRequest; import org.simantics.db.common.utils.NameUtils; import org.simantics.db.exception.DatabaseException; import org.simantics.db.service.VirtualGraphSupport; import org.simantics.layer0.Layer0;
public class VirtualGraphExample {
public Resource createLibrary(RequestProcessor processor, VirtualGraph vg, final String libraryName) throws DatabaseException { return processor.syncRequest(new WriteResultRequest<Resource>(vg) { @Override public Resource perform(WriteGraph graph) throws DatabaseException { Layer0 L0 = Layer0.getInstance(graph); Resource r = graph.newResource(); graph.claim(r, L0.InstanceOf, null, L0.Library); graph.claimLiteral(r, L0.HasName, libraryName); return r; } }); }
public void testVirtualGraphs(Session session) throws DatabaseException { VirtualGraphSupport vgSupport = session.getService(VirtualGraphSupport.class); VirtualGraph memory = vgSupport.getMemoryPersistent("memory"); VirtualGraph workspace = vgSupport.getWorkspacePersistent("workspace"); // NOTICE: resource are created in difference virtual graphs in separate // transactions through Session.syncRequest. Resource memResource = createLibrary(session, memory, "memory"); Resource workspaceResource = createLibrary(session, workspace, "workspace"); printVirtualGraphs(session); }
public void testMultipleVirtualGraphsInSameTransaction(Session session) throws DatabaseException { final VirtualGraphSupport vgSupport = session.getService(VirtualGraphSupport.class); session.syncRequest(new WriteRequest() { @Override public void perform(WriteGraph graph) throws DatabaseException { VirtualGraph memory = vgSupport.getMemoryPersistent("memory"); VirtualGraph workspace = vgSupport.getWorkspacePersistent("workspace"); // NOTICE: resource are created in different virtual graphs in // the same transaction through WriteGraph.syncRequest Resource memResource = createLibrary(graph, memory, "memory"); Resource workspaceResource = createLibrary(graph, workspace, "workspace"); } }); printVirtualGraphs(session); }
public void printVirtualGraphs(Session session) throws DatabaseException { session.syncRequest(new ReadRequest() { @Override public void run(ReadGraph graph) throws DatabaseException { VirtualGraphSupport vgSupport = graph.getService(VirtualGraphSupport.class); for (VirtualGraph vg : vgSupport.listGraphs()) { for (Statement stm : vgSupport.listStatements(vg)) { System.out.println("Statement: " + NameUtils.toString(graph, stm)); } for (Resource r : vgSupport.listValues(vg)) { System.out.println("Literal value: " + graph.getValue(r)); } } } }); }
} </syntaxhighlight>