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Comment by zomglings | Hacker News Reader

I only use RDF triples as a storage format for edges. I don't normally take advantage of triple stores (e.g. apache Jena), sparql query engines, etc.

It's just a simple format and it's easy to build different types of query/analysis capabilities around.

The only thing that's a little awkward is applying types to items in an rdf triple (in a way that's computationally cheap). Typing is a general problem, though.

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I strongly agree with this - RDF is fine and there are some great concepts in the SemWeb world (IRIs for example), but OWL and SPARQL are confusing and can be off-putting, especially when it is all rolled together. The latest iteration of our triple store actually moves radically towards linked-document or a 'document graph' to make it more understandable while keeping RDF at the base.

What is your triple store?

Can you express graph attributes such as edge weight in RDF?

I am familiar with RDF triples such as "Book", author, "Jane Doe". How would you express "10 minute phone call at time t between persons A and B"?

Not previous commenter, but as with other problems in computing, I find that you need to add a level of indirection.

    "CallSessionX" -> participant -> "person A"
    "CallSessionX" -> participant -> "person B"
    "CallSessionX" -> duration -> "10 minute"
    "CallSessionX" -> at_time -> t

Haven't used Sparql or Cypher in many years (used in Neo4j), but with the later you could do a query along the lines

   "person A" <- participant <- call_session -> participant -> "person B"

To find calls between person A and person B, then you can add a variable binding on the exact node you're interested in (eg call_session) to extract/aggregate attributes.

You could do it, but a triple wouldn't be the best choice of data structure. I would just add a new numerical column called "weight" to each relation in your RDF store:

    "Harry Potter and the Philosopher's Stone","author","Jane Doe",0.005

    "Harry Potter and the Philosopher's Stone","author","J.K. Rowling",1.0

    ...

You could easily export RDF triples from this if you needed to using rules like "The author for each book is determined by the '<book>-author-<name>' relation of highest weight".

Edit: Sorry I didn't answer your question about "10 minute phone call at time t between person A and person B".

The best way I can think of to model this with triples is:

    "call:<call_id>","started_at",t
    "call:<call_id>","ended_at",t + <duration>
    "person A","participant","call:<call_id>"
    "person B","participant","call:<call_id>"

But this may be overly complicated depending on how you want to query the data and what you want to do with it.

Edit 2: mhitza already answered it better! https://news.ycombinator.com/item?id=28503097

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