I have a SPARQL/Update query likes below.
INSERT { <http://localhost:8080/resource/User/166> rdf:type seagent:User;
seagent:User.email 'xyz#gmail.com'.
}
After execution of this query user has been inserted but properties of user not. How can I solve this problem?
Thanks in advance.
Following the question and answer at DBpedia SPARQL query that has a period in it, your query probably fails (apparently gracefully) on the period (.) in the predicate seagent:User.email.
You can expand the prefix to the property's full URI <http://example.org/#User.email> or define a different prefix PREFIX seagent-user: <http://example.org/#User.> and use that: ... seagent-user:email 'xyz#gmail.com'.
However, you may want to review the URIs for the properties and remove periods to avoid this kind of problems, if this is your own ontology. Or you could use a well known ontology like FOAF that includes properties to link email address to a person or user account.
Related
I am using this client
http://yasgui.laurensrietveld.nl
and I hope to query bioportal http://bioportal.bioontology.org
Most of my prior queries had a PREFIX and no FROM part. Can I move any FROM URL into PREFIX?
Using YASGUI client, what is the difference between FROM and the Endpoint field?
Can I rewrite any query with a from statement into a query that does not have it?
I am not able to list for example details of Human Phenotype Ontology concept id: HP:0000023 because I am not sure what to put into FROM or if to use it at all.
There are a number of terms and mechanisms here. Let's go over them one by one.
First of all, a PREFIX clause is simply a declaration of a syntax shortcut, for use within your query. So this line:
PREFIX ex: <http://example.org/>
says that the string ex: is a shortcut for the string http://example.org/. If you have this prefix declared at the start of your query, you can use ex:someUrl (instead of <http://example.org/someUrl>) in other places in your query. It's simply there to make queries easier to read and write, but apart from that it has no influence on the meaning of your query.
A SPARQL endpoint is another term for a web service that can answer SPARQL queries.
The FROM clause of a SPARQL query determines the dataset (or more precisely, the default graph, which is part of the dataset) over which the query is executed. Any SPARQL endpoint may contain several graphs, each identified by a URI (so-called named graphs). A collection of such graph together is a dataset. If you don't specify a FROM clause (and perhaps also one or more FROM NAMED clauses), the dataset queried is simply whatever default dataset the endpoint chooses.
So, what this mean for your specific questions?
Most of my prior queries had a PREFIX and no FROM part. Can I move any FROM URL into PREFIX?
As you can see from the above explanation, that would make no sense. They are different mechanisms, for different purposes, that just both happen to use URIs.
Using YASGUI client, what is the difference between FROM and the Endpoint field?
The endpoint field defines which service YASGUI needs to send the query to. The FROM clause tells the endpoint what dataset you want to query.
Can I rewrite any query with a from statement into a query that does not have it?
Not generally, no. The absence of a FROM clause means that the endpoint executes the query over its default dataset. Depending on how that endpoint is configured, this may mean that you either get a lot more results (namely not just from the one dataset you want, but from a lot of others) or none at all (in case the dataset you wanted to query is not part of the endpoint's default dataset).
I have REST API URL structure similar to:
/api/contacts GET Returns an array of contacts
/api/contacts/:id GET Returns the contact with id of :id
/api/contacts POST Adds a new contact and return it with an id added
/api/contacts/:id PUT Updates the contact with id of :id
/api/contacts/:id PATCH Partially updates the contact with id of :id
/api/contacts/:id DELETE Deletes the contact with id of :id
My question is about:
/api/contacts/:id GET
Suppose that in addition to fetching the contact by ID, I also want to fetch it by an unique alias.
What should be URI structure be if I want to be able to fetch contact by either ID or Alias?
If you're alias's are not numeric i would suggest using the same URI structure and figuring out if it's an ID or an alias on your end. Just like Facebook does with username and user_id. facebook.com/user_id or facebook.com/username.
Another approach would be to have the client use GET /contacts with some extra GET parameters as filters to first search for a contact and then looking up the ID from that response.
Last option i think would be to use a structure like GET /contacts/alias/:alias. But this would kinda imply that alias is a subresource of contacts.
The path and query part of IRIs are up to you. The path is for hierarchical data, like api/version/module/collection/item/property, the query is for non-hierarchical data, like ?display-fields="id,name,etc..." or ?search="brown teddy bear"&offset=125&count=25, etc...
What you have to keep in mind, that you are working with resources and not operations. So the IRIs are resource identifiers, like DELETE /something, and not operation identifiers, like POST /something/delete. You don't have to follow any structure by IRIs, so for example you could use simply POST /dashuif328rgfiwa. The server would understand, but it would be much harder to write a router for this kind of IRIs, that's why we use nice IRIs.
What is important that a single IRI always belongs only to a single resource. So you cannot read cat properties with GET /cats/123 and write dog properties with PUT /cats/123. What ppl usually don't understand, that a single resource can have multiple IRIs, so for example /cats/123, /cats/name:kitty, /users/123/cats/kitty, cats/123?fields="id,name", etc... can belong to the same resource. Or if you want to give an IRI to a thing (the living cat, not the document which describes it), then you can use /cats/123#thing or /users/123#kitty, etc... You usually do that in RDF documents.
What should be URI structure be if I want to be able to fetch contact
by either ID or Alias?
It can be /api/contacts/name:{name} for example /api/contacts/name:John, since it is clearly hierarchical. Or you can check if the param contains numeric or string in the /api/contacts/{param}.
You can use the query too, but I don't recommend that. For example the following IRI can have 2 separate meanings: /api/contacts?name="John". You want to list every contact with name John, or you want one exact contact. So you have to make some conventions about this kind of requests in the router of your server side application.
I would consider adding a "search" resource when you are trying to resolve a resource with the alias:
GET /api/contacts/:id
and
GET /api/contacts?alias=:alias
or
GET /api/contacts/search?q=:alias
First of all, the 'ID' in the URL doesn't have to be a numerical ID generated by your database. You could use any piece of data (including the alias) in the URL, as long as its unique. Of course, if you are using numerical ID's everywhere, it is more consistent to do the same in your contacts API. But you could choose to use the aliases instead of numeric IDs (as long as they are always unique).
Another approach would be, as Stromgren suggested, to allow both numeric IDs and aliases in the URL:
/api/contacts/123
/api/contacts/foobar
But this can obviously cause problems if aliases can be numeric, because then you wouldn't have any way to differentiate between an ID and a (numeric) alias.
Last but not least, you can implement a way of filtering the complete collection, as shlomi33 already suggested. I wouldn't introduce a search resource, as that isn't really RESTful, so I'd go for the other solution instead:
/api/contacts?alias=foobar
Which should return all contacts with foobar as alias. Since the alias should be unique, this will return 1 or 0 results.
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 am working on semantic web project where user will input text query like "Name the presidents of US who died under an age of 60 ? " and I have to generate automatic sparql query based on user's inputed text and this will be fired on http://dbpedia.org/snorql using DBpedia endpoint. I am confused how to select subject, predicate and object as we don't know all properties of specific resource.
Check out GATE (general architecture for text engineering).
I suppose you could analyze the natural query, and with Annie and JAPE, you might have a good start to transform your query into sparql.
Hope this helps