Database Reference
In-Depth Information
Fig. 5 shows the contin
nodes selected by the XPat
is the grammar DAG (as sh
and containing the follow
(HGE(X)', 1, JB(X)'), (JB(
For the root node S' of
additional outgoing edges
Therefore, within lines (
(S',1,CDE(X)) and (S',3,CD
For the UD node HGE
additional outgoing edge, i
also applies to the UD node
Now, the isolation phase
within the copied grammar
set of paths selected by the
the node reLTo(z) from the
Finally, the nodes S and
as they are not reachable fr
Fig. 5(b).
nued example of the isolation process for re-labeling
th expression //h//b to z. The input of the isolation proc
hown in Fig. 3) and the update DAG (UD) shown in Fig
wing set of edges: { (S',2,HGE(X)'), (S',4,HGE(X
X)',1,reLTo(z)) }.
f the UD, the corresponding node S of the GD has t
at the index positions 1 and 3 to the node CDE(
(2)-(4), Algorithm 1 extends the UD with the ed
DE(X)) from S' to CDE(X).
E(X)', the corresponding node HGE(X) in GD has
.e. no outgoing edge from HGE(X)' has to be added. T
e JB(X)'.
e is completed, and replacing the terminal symbol b wit
rule represented by the node JB (X)' modifies exactly
e XPath query //h//b to have the new label z, and remo
EUD.
HGE(X) and their outgoing edges can be deleted from
rom any path starting in S'. The resulting UD is shown
the
cess
g. 4
X)'),
two
(X).
dges
no
That
th z
the
oves
GD
n in
Fig. 5.
Isolation
of nodes selected by //h//b for re-labeling them to z
Note that we implement
represented by GD. For exa
S', HGE(X)', and JB(X)' a
and HGE(X)' instead of H
JB(X) is called from the H
JB'(X) rule in the following
t UD nodes by copying grammar rules from the gramm
ample, Grammar 3 is modified in such a way that the ru
are copied from the rules S, HGE, and JB(X) respectiv
HGE(X) is called from the S' rule, and JB(X)' instead
HGE(X)' rule. Then, b can be replaced with z within
g update step.
mar
ules
ely,
d of
the
3.4 Performing the Upda
ates
After UD isolation by exte
each edge (U
i
, I, U) in EUD
ending the UD to a EUD in lines (1)-(6) of Algorithm
D to an update leaf node U, i.e. a leaf node of EUD wh
m 1,
here
