Question

Allegrograph is basically a RDF triple(actually five field) store. Then why can’t we create a MySQL table with five columns and store the triples in them. ?

What features does AG have over such MySql table ?

Answer 1

Simply put it supports SPARQL

SPARQL is the query language for RDF and it has quite difference semantics to SQL, there are tools to convert SPARQL into SQL queries but performance is often very poor. Plus there are lots of features of the SPARQL specification (esp the built-in functions) which have no equivalent in MySQL and so would either have to be aped by stored procedures/user defined functions or done in code.

Evaluating SPARQL is quite different to evaluating SQL because SPARQL is far more reliant on lots of complex joins, SPARQL stores use optimizers that while work on the same principles as SQL optimizers but are designed to cope with very different kinds of queries to those a traditional RDBMS would usually handle.

In general a five column table is very naive because each column contains a complex item that has multiple parts to it and would be better stored using multiple tables. Also a single table approach will lead to massive storage requirements over a more normalized table design.

If all you care about is saving and loading RDF triples to/from an SQL database then a naive single table approach may be fine for you. If you actually want to do something useful then you need a more complex SQL database schema or a proper RDF store like AllegroGraph