Databases Reference
In-Depth Information
We show another example:
We can write simple conditions in
l-attr
,
however we have to use
e-attr
or name
space for complex conditions, because
l-attr
is only in the form of a flat tuple.
3.2.5
Document Groups
A document group is a logical unit of multiple documents to be treat as one. The
group is defined as follows:
where
g
is a logical document consisting of
g
1
,
g
2
, ….,
g
n
. As this unit is arbitrary,
it must be explicitly specified. If the ordering among elements is important,
const
=
“list”
can be specified with
doc_group
.
4
Document Operations
To define document operations, we have to make various concepts clear: relation
between graph and access path, logical operations, and normalization of a set of
graphs or access paths.
4.1
Access by Paths and Identifiers
We can consider two different accesses as follows:
