I am looking for a query in sparql language that will return the number of classes that have attributes (I think object properties are the attributes) - does anyone have an idea?
I am using this website -> http://139.91.210.25:8890/sparql to run my queries and I use this dataset name http://localhost:8890/pizza. Thank you very much
Related
In short, if someone instructs me, "Get a list of databases which include Oracle, Mysql, DB2, MSSQL, etc.," how can I actually establish which fields and information I need to create the query? I downloaded DBpedia and grepped the triples, e.g.,
$ `grep 'Oracle' * | grep 'Database'
article_categories_en.nt:<http://dbpedia.org/resource/Oracle_Database> <http://purl.org/dc/terms/subject> <http://dbpedia.org/resource/Category:Relational_database_management_systems> .`
How do I create a SPARQL query from that initial question?
Using that snippet above, I know Oracle is a company and one of its products is an RDBMS by the same name. I tried the lookup tool and searching the web but did not get far enough with this and need some direction.
In this particular case, I'd start by visiting the DBpedia page corresponding to one of the things that you know you'd like in your result. A good instance is http://dbpedia.org/page/MySQL. On that page, you can start to look for properties that might help you find other related systems. One property listed on the page is
dbpedia-owl:genre dbpedia:Relational_database_management_system
Then I'd go the DBpedia SPARQL endpoint and try searching for other things that have this same property and value. In this case, I can run the following query:
SELECT * WHERE {
?rdbms dbpedia-owl:genre dbpedia:Relational_database_management_system .
}
SPARQL results
The results are pretty promising; there are 38 results. The first few are:
rdbms
http://dbpedia.org/resource/MySQL_Cluster
http://dbpedia.org/resource/MSQL
http://dbpedia.org/resource/OpenEdge_Advanced_Business_Language
http://dbpedia.org/resource/Adaptive_Server_Enterprise
…
In general, I find it much easier to locate an instance of the sort of thing that I'm looking for in Wikipedia, then visit the corresponding DBpedia page and look at the properties, and then formulate some exploratory queries based on that.
I want to get results from sparql query and the results contain no namespace.
ex: there is result in triple format like:
"http://www.xyz.com#Raxit" "http://www.w3.org/1999/02/22-rdf-syntax-ns#type" "http://www.xyz.com#Name"
So i want to get only following:
Raxit type Name
I want to get this results directly from sparql query. I am using virtuoso.
Is it possible to get this from sparql?
Please share your thoughts regarding this.
Thanks in Advance.
If your data is regular, and you know that the sub-string you want always occurs after a # character, then you can use the strafter function from SPARQL 1.1. I do not know whether this is available in Virtuoso's implementation or not.
However this is, in general, a very risky strategy. Not all URI's are formatted with a local name part after a # character. In fact, in general, a URI may not have a legal or useful localname at all. So you should ask yourself: why do you think you need this? Generally speaking, a semantic web application uses the whole URI as an indivisible identifier. If your need is actually for something human-friendly to display in a UI, have your query also look for rdfs:label or skos:label properties. Worst case, try to abbreviate the URI to q-name form (i.e. prefix:name), using the prefixes from the model or a service like prefix.cc
The simplest way to achieve this is to not bother with adapting your query, but to just post-process the result yourself. Depending on which client library you use to communicate with Virtuoso, you will typically find it has API support to parse the result, get back values, and for each value then get only local name (I suggest you look for a URI.getLocalName() method or something similar).
I'm a bit green with the criteria api. So far, I've been able to get a list of nhibernate objects by using .List().ToList() on an ICriteria object.
I was just wondering if it was possible, say, to get a list of ints of all the ID #s of the objects that would have been returned, instead of returning the objects.
I know you can do this with HQL but I'm searching the database with dynamic lists from the user gui so the criteria api seems to be the better option.
Thanks.
Isaac
You can use Projections to return only a subset of the properties of an object.
im pretty confused about lambdas and actually im not even sure i need them here
what im trying to do here is write a function that will return an object from a certain table with a certain criteria
so lets say i can write
function GetRecord(TableName as string,Criteria as string) as object
'do the linq-stuff
end function
now i dont care if the paremeters are strings or lambdas or whatever, but the end result must be that at runtime i dont know which table and which criteria will be used
as sometimes i need to get a customer record by email and sometimes a product by id etc.
if possible i would prefer returning a list of matching objects and then i would just use .firstordefault when i want 1 (such as by id...)
thank you , as always, for taking the time to read this and answer!
all the best
Have you considered using Dynamic LINQ?
Example:
Parsing an expression tree can be a challenging but rewarding method of solving this issue. I think it's overkill and I'd go with Dynamic Linq as decyclone mentioned.
A benefit of parsing the expression tree, however, is that you can have compile time checking of the submitted criteria.
Here are some articles that helped me.
How to: Implement an Expression Tree Visitor: http://msdn.microsoft.com/en-us/library/bb882521(VS.90).aspx
Building a custom IQueryable Provider: http://blogs.msdn.com/b/mattwar/archive/2008/11/18/linq-links.aspx
Walkthrough: Creating an IQueryable LINQ Provider: http://msdn.microsoft.com/en-us/library/bb546158(v=VS.90).aspx
Expression Tree Basics:
http://blogs.msdn.com/b/charlie/archive/2008/01/31/expression-tree-basics.aspx
I knew this might be a stupid question but I don't know the answer :)
I am using protege4 I built my ontology and when I tried to use DL Query from the DL query tap in protege4 it executes fine and I get results.
However, when I click "Add to ontology" to add my query to the ontology it adds it but without any query results!!! Why are there no query results? and how to see it?
Thanks
First some terminology:
Every OWL ontology is a set of OWL axioms.
Every DL-Query is an OWL class expression.
Every DL-Query result is a set of OWL entities.
You can only add axioms to an ontology. You cannot add class expressions nor sets of entities to an OWL ontology.
The "Add to ontology" button seems to create a new EquivalentClasses-axiom on the basis of the query (i.e. class expression), and a named class (given by the user), and then asserts this axiom into the active ontology, i.e.
EquivalentClasses(new_name query)
(I didn't quite get it working like this in my version of Protege 4, but such a functionality would make sense.)
The current OWL2 specification does not say anything about how to store class expressions and query results in the ontology. These have to be specified and calculated every time from scratch after you load the ontology from the file.