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Samizdat Developer's Notes
==========================
RDF Aggregates
--------------
Application:
- Version Tracking
- Structured Documents
- Stored Queries
Requirements
- Tree Walking
- Sequence
Version Tracking: dct:isVersionOf
problem: how to extract n-th version of a document in a relational RDF
store without n-way join? - add special construct to Squish to express
repetitive RDF arcs (repetitive property grounding)
Example of 4th Item Extraction:
SELECT ?fourth
WHERE (s:next ex:head ?second)
(s:next ?second ?third)
(s:next ?third ?fourth)
SELECT s3.subject AS fourth
FROM Statement s1, Statement s2, Statement s3,
Resource r1, Resource r2
WHERE s1.property = r1.id AND r1.label = 's:next'
AND s1.subject = r2.id AND r2.label = 'ex:head'
AND s2.property = r1.id
AND s1.object = s2.subject
AND s2.property = r1.id
AND s2.subject = s3.object
SELECT ?fourth
WHERE (s:next*3 ex:head ?fourth)
CREATE FUNCTION property_chain_counted(property, head, count) RETURNS int AS
DECLARE
i int;
next int;
BEGIN
i := 1; next := head;
WHILE i <= count AND next IS NOT NULL DO BEGIN
SELECT INTO :next s.object FROM Statement s
WHERE s.property = property AND s.subject = next;
i := i + 1;
END;
RETURN :head;
END;
CREATE FUNCTION property_chain_match(property, head, tail) RETURNS int AS
DECLARE
i int;
next int;
BEGIN
i := 0; next := head;
WHILE next <> tail AND next IS NOT NULL DO BEGIN
SELECT INTO :next s.object FROM Statement s
WHERE s.property = property AND s.subject = next;
i := i + 1;
END;
RETURN i;
END;
(ns:property * ?count ?head ?tail)
2 cases: 1) property is mapped to a table; 2) generic property.
SELECT field FROM table WHERE id =
Transparent Query Storage
-------------------------
Argument for transparent (structured) query storage: ability to analyze,
find similar, merge, etc.
Separate Schema namespace: http://.../samizdat/query.
sq:mustBind
sq:triples
sq:literalCondition
sq:orderBy
sq:cache
Can rdf:Statement.rdf:subject contain a blank node name?
In relational storage, Statement.subject refers to Resource.id, so it
looks like the trick is to add a blank_node boolean field.
If uriref in Squish query is already stored in the site KB,
Query.triples.li.Statement should refer to the Resource.id. This means,
each uriref in a query text should be looked up for id.
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