Extent visibility

When looking for matches, queries only consider Node that are in their set of visible extents.

An extent collects its nodes not by a single list, but by a number of (doubly linked) lists. Currently, 16 lists are used, but this can easily be changed. This feature is used to partition the extents. The 16 lists are called the extent indexes.

Extents are used by the query graph to access the nodes of the graph. In this process, nodes can be “hidden” to queries by being on a extent index non visible by the query scope (see RGG's extent index visibility). Non visible nodes are not visited and “ignored” by the queries, they are not visited at all (thus, efficient to speed up queries). For the RGG model graph, queries use only the seven first indexes by default. The default index usage is:

0 to 6: Default visibility - used by default in queries. Only these indexes are visible by default.
7: Meta data index.
8: Type graph data - used for the multi-scales.
9 to 15: Unused indexes - non visible by default.

Note: the index visibility is not used for the display. Thus, nodes on a “non” visible index are still displayed in the 3d view.

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Default visibility

Every query whose visibility is not explicitly declared will use the default visibility. The default value for RGG models is 127 (i.e. 0b1111111).

The default extent visibility can be set with:

{de.grogra.rgg.model.Runtime.INSTANCE.currentGraph().setVisibleExtents( 0b1111111 );}

Explicit visibility declaration

It is also possible to change the extent visibility for only one query. The extent visibility can declared explicitly with: @ VAL ; QVDECL; QUERY where VAL is the visibility value. (QVDECL is the query variable declaration, and QUERY the query).

For example:

void rule() [
  @5; A ==> B;  // match all A in the extents 1, 2, and 3
  @1; A ==> B; // match all A in the extent 1
  A ==> B; // match all A in the default extents (i.e. 1 to 7)
]
void meth(){
  (* @21; F *); // match all F in the extents 1, 3, and 5
}

Example

For instance, let's consider the following method in an empty project. Notice that we set the visible extent value to 1:

public void run(){
de.grogra.rgg.model.Runtime.INSTANCE.currentGraph().setVisibleExtents(1);
println((*Node*));
}

The method output:

de.grogra.rgg.RGGRoot[id=99]@2e86af42
de.grogra.rgg.Axiom[id=100]@59f1c976

Only the “normal” nodes are visible.

Let's change the visible extent value to 255. Now the method output:

de.grogra.graph.impl.Node[id=0]@5add4889
de.grogra.graph.impl.Node[id=1]@4f690d55
de.grogra.rgg.RGGRoot[id=103]@621de1a6
Model[id=101]@331e288e
parameters[id=102]@cd97a89
de.grogra.rgg.Axiom[id=104]@4cface1f

Some additional nodes are now visible:

the roots (id 0 and 1). id 0 is the root of the main graph. id 1 is the root of the meta graph.
the nodes from the meta graph: the compiled version of the files: Model, and parameters.

Notice that:

Once the setVisibleExtents is called. The value remains until a new value is set.
setVisibleExtents use as parameter the decimal value of a binary number of 8 values where each 1 mean that the index is visible, the 0 to 7 index visibility are defined from left to right. E.g. to have all indexes visible, we use 11111111 (eight 1), which is equal in decimal to 255. To have all indexes visible except for the 1rst one, we use 11111110 (=254). The default value is 01111111 (=127).

Table of Contents

Extent visibility

Default visibility

Explicit visibility declaration

Example