'SELECT' command in SQL, but has the advantage of applying to tree
structures, which are more general than relations. That is, while a
relation (a table) has a depth = 2, a tree can have an arbitrary
-depth. This property allows us to consicely refer to 'the nodes in the
+depth. This property allows us to consicely refer to criteria such as 'the nodes in the
site corresponding to a user named Alice.' This particular command
might look like: '/user[name='Alice']/site/node.'
* Some terms have an '@' in them, meaning that they are attributes;
e.g., to retrieve the value of p in the following data, we would use
- the expression "//x/y/@p"
+ the expression "/x/y/@p"
<x>
<y p="q"/>
different format.
Example target
-------------
+--------------
Targets are specified just like matches. If you haven't read the match
example, then now is a good time to do that. Here's an example target:
Contexts
--------
-Matches and targets are associated with specific contexts. A target
-may use a variety of criteria to process a request, and may need to
-look them up in the SFA database. The 'context' contains an xpath
-expression that isolates the items that a match refers to. The XML
-spec corresponding to this expression corresponds to an abstract
-database schema defined as part of the library. SFA is responsible for
-evaluating this expression, obtaining the data items that the match
-needs and providing them to the match at the time of evaluation.
+Matches and targets are associated with specific contexts. A target may use a
+variety of criteria to process a request, and may need to look them up in the
+SFA database. The 'context' contains an xpath expression that isolates the
+items that a match or target may refer to. For example, if a match needs access
+to the nodes corresponding to a slice's site, then the context may be '/sfa/slice[@name=/context/slice/@name]/nodes'.
+
Here's a summary of the model:
--------------------------
+-----------------------------
An AM can inherit from a set of elements (E).