Semantic Web, Structured Dynamics, OSF Web Services

Querying the MyPeg datasets using the structWSF SPARQL endpoint

The last blog post I wrote demonstrated how one could query the MyPeg.ca portal using the full set of structWSF web service endpoints to get data out of the portal. However, I didn’t cover the usage of the SPARQL endpoint since I wanted to cover it in its own blog post to explain all its characteristics.

In this blog post, I will demonstrate how one can get data out of the MyPeg.ca community indicators web portal for Winnipeg’s citizens using the SPARQL endpoint. I will also cover all the specificities of this SPARQL endpoint: all its characteristics and access/permission features.

Two Modes

The first characteristic of the structWSF SPARQL endpoint is that there are two modes (usecases) it can be used for:

  1. Getting SPARQL resultsets that match some SPARQL queries patterns
  2. Getting complete records descriptions in any format supported by the endpoint

The first mode is not different than any other SPARQL endpoint. Users just send different SPARQL queries and retrieve their related SPARQL resultsets. These resultsets can be returned using different MIME types.

For a SELECT query, these formats can be used:

  1. application/sparql-results+xml
  2. application/sparql-results+json

For a DESCRIBE or a CONSTRUCT query, these formats can be used:

  1. text/rdf+n3 (RDF+N3)
  2. application/rdf+xml (RDF+XML)
  3. application/rdf+json (RDF+JSON)
  4. text/plain (NTRIPLES)

The second mode is quite different. The main characteristic of the structWSF SPARQL endpoint is that it can export resultsets into different formats, not usually supported by other endpoints. However, these other formats are usually used to describe complete descriptions of records, and not just some triples matching some SPARQL patterns.

For that reason, the SPARQL query that is sent using this second mode needs to have the three variables (1) ?s, (2) ?p and (3) ?o bound in the SPARQL query, otherwise an empty resultset will be returned. For example, the following SPARQL query would return the complete records descriptions of all the records that are peg:Theme and that are themes of the peg:WellBeing cross cutting issue:

[cc lang=’text’ line_numbers=’false’ escaped=’true’]SELECT ?s ?p ?o
WHERE
{
?s a <http://purl.org/ontology/peg#Theme> ;
<http://purl.org/ontology/peg#isThemeOf> <http://purl.org/ontology/peg/framework#WellBeing> ;
?p ?o .
}[/cc]

This mode is used to return a set of records descriptions that match a SPARQL pattern. Supported MIME formats for that second mode are:

  • text/xml (structXML)
  • application/json (structXML in JSON)
  • application/rdf+xml (RDF+XML)
  • application/rdf+n3 (RDF+N3)
  • application/sparql-results+xml (SPARQL resultset in XML)
  • application/sparql-results+json (SPARQL resultset in XML)

Getting Records in Different Formats

Now, let’s take a look at what is returned for the SPARQL query above, for each of these supported MIME types, from the MyPeg.ca SPARQL endpoint.

Note that the queries below are using the Curl application (available for multiple operating systems) to send the HTTP queries to the structWSF SPARQL web service endpoint.

StructXML: text/xml

[cc lang=’text’ line_numbers=’false’ escaped=’true’]
curl -H “Accept: text/xml” “http://www.mypeg.ca/ws/sparql/” -d “dataset=http://www.mypeg%2Eca%2Fwsf%2Fdatasets%2F249%2F&query= SELECT+%3Fs+%3Fp+%3Fo%0D%0AWHERE%0D%0A{%0D%0A++%3Fs+a+<http%3A%2F%2Fpurl.org%2Fontology%2Fpeg%23Theme>+%3B%0D%0A+<http%3A%2F%2Fpurl.org%2Fontology%2Fpeg%23isThemeOf>+<http%3A%2F%2Fpurl.org%2Fontology%2Fpeg%2Fframework%23WellBeing>+%3B%0D%0A+++++%3Fp+%3Fo+.%0D%0A}%0D%0A”
[/cc]

[cc lang=’xml’ line_numbers=’false’ escaped=’true’]

<?xml version=”1.0″ encoding=”utf-8″?>
<resultset>
<prefix entity=”owl” uri=”http://www.w3.org/2002/07/owl#”/>
<prefix entity=”rdf” uri=”http://www.w3.org/1999/02/22-rdf-syntax-ns#”/>
<prefix entity=”rdfs” uri=”http://www.w3.org/2000/01/rdf-schema#”/>
<prefix entity=”wsf” uri=”http://purl.org/ontology/wsf#”/>
<subject type=”http://purl.org/ontology/peg#Theme” uri=”http://purl.org/ontology/peg/framework#Economy”>
<predicate type=”http://purl.org/ontology/peg#isThemeOf”>
<object uri=”http://purl.org/ontology/peg/framework#WellBeing”/>
</predicate>
<predicate type=”http://purl.org/ontology/peg#isThemeOf”>
<object uri=”http://purl.org/ontology/peg/framework#Poverty”/>
</predicate>
<predicate type=”http://purl.org/ontology/sco#displayComponent”>
<object uri=”http://purl.org/ontology/sco#sRelationBrowser”/>
</predicate>
<predicate type=”http://www.w3.org/2000/01/rdf-schema#label”>
<object type=”rdfs:Literal”>economy</object>
</predicate>
<predicate type=”http://purl.org/ontology/iron#prefLabel”>
<object type=”rdfs:Literal”>Economy</object>
</predicate>
<predicate type=”http://purl.org/dc/elements/1.1/description”>
<object type=”rdfs:Literal”>Economy includes all that people do in our community to produce, exchange, distribute, and consume goods and services.</object>
</predicate>
</subject>
</resultset>

[/cc]

StructXML in JSON: application/json

[cc lang=’text’ line_numbers=’false’ escaped=’true’]

curl -H “Accept: application/json” “http://www.mypeg.ca/ws/sparql/” -d “dataset=http://www.mypeg%2Eca%2Fwsf%2Fdatasets%2F249%2F&query= SELECT+%3Fs+%3Fp+%3Fo%0D%0AWHERE%0D%0A{%0D%0A++%3Fs+a+<http%3A%2F%2Fpurl.org%2Fontology%2Fpeg%23Theme>+%3B%0D%0A+<http%3A%2F%2Fpurl.org%2Fontology%2Fpeg%23isThemeOf>+<http%3A%2F%2Fpurl.org%2Fontology%2Fpeg%2Fframework%23WellBeing>+%3B%0D%0A+++++%3Fp+%3Fo+.%0D%0A}%0D%0A”

[/cc]

[cc lang=’javascript’ line_numbers=’false’ escaped=’true’]

{
“prefixes”: [
{
“owl”: “http://www.w3.org/2002/07/owl#”,
“rdf”: “http://www.w3.org/1999/02/22-rdf-syntax-ns#”,
“rdfs”: “http://www.w3.org/2000/01/rdf-schema#”,
“wsf”: “http://purl.org/ontology/wsf#”,
“ns0”: “http://purl.org/ontology/peg#”,
“ns1”: “http://purl.org/ontology/sco#”,
“ns2”: “http://purl.org/ontology/iron#”,
“ns3”: “http://purl.org/dc/elements/1.1/”
}
],
“resultset”: {
“subject”: [
{
“uri”: “http://purl.org/ontology/peg/framework#Economy”,
“type”: “ns0:Theme”,
“predicates”: [
{
“ns0:isThemeOf”: {
“uri”: “http://purl.org/ontology/peg/framework#WellBeing”
}
},
{
“ns0:isThemeOf”: {
“uri”: “http://purl.org/ontology/peg/framework#Poverty”
}
},
{
“ns1:displayComponent”: {
“uri”: “http://purl.org/ontology/sco#sRelationBrowser”
}
},
{
“rdfs:label”: “economy”
},
{
“ns2:prefLabel”: “Economy”
},
{
“ns3:description”: “Economy includes all that people do in our community to produce, exchange, distribute, and consume goods and services.”
}
]
},
]
}
}

[/cc]

RDF in XML: application/rdf+xml

[cc lang=’text’ line_numbers=’false’ escaped=’true’]

curl -H “Accept: application/rdf+xml” “http://www.mypeg.ca/ws/sparql/” -d “dataset=http://www.mypeg%2Eca%2Fwsf%2Fdatasets%2F249%2F&query= SELECT+%3Fs+%3Fp+%3Fo%0D%0AWHERE%0D%0A{%0D%0A++%3Fs+a+<http%3A%2F%2Fpurl.org%2Fontology%2Fpeg%23Theme>+%3B%0D%0A+<http%3A%2F%2Fpurl.org%2Fontology%2Fpeg%23isThemeOf>+<http%3A%2F%2Fpurl.org%2Fontology%2Fpeg%2Fframework%23WellBeing>+%3B%0D%0A+++++%3Fp+%3Fo+.%0D%0A}%0D%0A”

[/cc]

[cc lang=’xml’ line_numbers=’false’ escaped=’true’]

<?xml version=”1.0″?>
<rdf:RDF  xmlns:owl=”http://www.w3.org/2002/07/owl#” xmlns:rdf=”http://www.w3.org/1999/02/22-rdf-syntax-ns#” xmlns:rdfs=”http://www.w3.org/2000/01/rdf-schema#” xmlns:wsf=”http://purl.org/ontology/wsf#” xmlns:ns0=”http://purl.org/ontology/peg#” xmlns:ns1=”http://purl.org/ontology/sco#” xmlns:ns2=”http://purl.org/ontology/iron#” xmlns:ns3=”http://purl.org/dc/elements/1.1/”>

<ns0:Theme rdf:about=”http://purl.org/ontology/peg/framework#Economy”>
<ns0:isThemeOf rdf:resource=”http://purl.org/ontology/peg/framework#WellBeing” />
<ns0:isThemeOf rdf:resource=”http://purl.org/ontology/peg/framework#Poverty” />
<ns1:displayComponent rdf:resource=”http://purl.org/ontology/sco#sRelationBrowser” />
<rdfs:label>economy</rdfs:label>
<ns2:prefLabel>Economy</ns2:prefLabel>
<ns3:description>Economy includes all that people do in our community to produce, exchange, distribute, and consume goods and services.</ns3:description>
</ns0:Theme>

</rdf:RDF>

[/cc]

RDF in N3: application/rdf+n3

[cc lang=’text’ line_numbers=’false’ escaped=’true’]

curl -H “Accept: application/rdf+n3” “http://www.mypeg.ca/ws/sparql/” -d “dataset=http://www.mypeg%2Eca%2Fwsf%2Fdatasets%2F249%2F&query= SELECT+%3Fs+%3Fp+%3Fo%0D%0AWHERE%0D%0A{%0D%0A++%3Fs+a+<http%3A%2F%2Fpurl.org%2Fontology%2Fpeg%23Theme>+%3B%0D%0A+<http%3A%2F%2Fpurl.org%2Fontology%2Fpeg%23isThemeOf>+<http%3A%2F%2Fpurl.org%2Fontology%2Fpeg%2Fframework%23WellBeing>+%3B%0D%0A+++++%3Fp+%3Fo+.%0D%0A}%0D%0A”

[/cc]

[cc lang=’text’ line_numbers=’false’ escaped=’true’]

@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix wsf: <http://purl.org/ontology/wsf#> .

<http://purl.org/ontology/peg/framework#Economy> a <http://purl.org/ontology/peg#Theme> ;
<http://purl.org/ontology/peg#isThemeOf> <http://purl.org/ontology/peg/framework#WellBeing> ;
<http://purl.org/ontology/peg#isThemeOf> <http://purl.org/ontology/peg/framework#Poverty> ;
<http://purl.org/ontology/sco#displayComponent> <http://purl.org/ontology/sco#sRelationBrowser> ;
<http://www.w3.org/2000/01/rdf-schema#label> “””economy””” ;
<http://purl.org/ontology/iron#prefLabel> “””Economy””” ;
<http://purl.org/dc/elements/1.1/description> “””Economy includes all that people do in our community to produce, exchange, distribute, and consume goods and services.””” .

[/cc]

Getting Records Using CONSTRUCT

You always have the possibility to use a CONSTRUCT query to return data in different formats. Unlike with the second mode supported by the endpoint, you won’t have access to different formats (such as structXML both in XML and JSON). Here is such a CONSTRUCT query:

[cc lang=’text’ line_numbers=’false’ escaped=’true’]
CONSTRUCT FROM <http://www.mypeg.ca/wsf/datasets/249/>
{
?s ?p ?o .
}
WHERE
{
?s peg:isThemeOf <http://purl.org/ontology/peg/framework#WellBeing> .
?s ?o ?p .
}
[/cc]

[cc lang=’text’ line_numbers=’false’ escaped=’true’]
curl -H “Accept: application/rdf+xml” “http://www.mypeg.ca/ws/sparql/” -d “query=PREFIX%20peg%3A%20%3Chttp%3A%2F%2Fpurl.org%2Fontology%2Fpeg%23%3E%0ACONSTRUCT%0A%7B%0A%20%20%3Fs%20peg%3AisThemeOf%20%3Chttp%3A%2F%2Fpurl.org%2Fontology%2Fpeg%2Fframework%23WellBeing%3E%20.%0A%7D%0AFROM%20%3Chttp%3A%2F%2Fwww.mypeg.ca%2Fwsf%2Fdatasets%2F249%2F%3E%0AWHERE%20%0A%7B%20%0A%20%20%3Fs%20peg%3AisThemeOf%20%3Chttp%3A%2F%2Fpurl.org%2Fontology%2Fpeg%2Fframework%23WellBeing%3E%20.%0A%7D”
[/cc]

[cc lang=’xml’ line_numbers=’false’ escaped=’true’]
<?xml version=”1.0″ encoding=”utf-8″ ?>
<rdf:RDF xmlns:rdf=”http://www.w3.org/1999/02/22-rdf-syntax-ns#” xmlns:rdfs=”http://www.w3.org/2000/01/rdf-schema#”>
<rdf:Description rdf:about=”http://purl.org/ontology/peg/framework#EducationAndLearning”><n0pred:isThemeOf xmlns:n0pred=”http://purl.org/ontology/peg#” rdf:resource=”http://purl.org/ontology/peg/framework#WellBeing”/></rdf:Description>
<rdf:Description rdf:about=”http://purl.org/ontology/peg/framework#BasicNeeds”><n0pred:isThemeOf xmlns:n0pred=”http://purl.org/ontology/peg#” rdf:resource=”http://purl.org/ontology/peg/framework#WellBeing”/></rdf:Description>
<rdf:Description rdf:about=”http://purl.org/ontology/peg/framework#Health”><n0pred:isThemeOf xmlns:n0pred=”http://purl.org/ontology/peg#” rdf:resource=”http://purl.org/ontology/peg/framework#WellBeing”/></rdf:Description>
<rdf:Description rdf:about=”http://purl.org/ontology/peg/framework#SocialVitality”><n0pred:isThemeOf xmlns:n0pred=”http://purl.org/ontology/peg#” rdf:resource=”http://purl.org/ontology/peg/framework#WellBeing”/></rdf:Description>
<rdf:Description rdf:about=”http://purl.org/ontology/peg/framework#BuiltEnvironment”><n0pred:isThemeOf xmlns:n0pred=”http://purl.org/ontology/peg#” rdf:resource=”http://purl.org/ontology/peg/framework#WellBeing”/></rdf:Description>
<rdf:Description rdf:about=”http://purl.org/ontology/peg/framework#NaturalEnvironment”><n0pred:isThemeOf xmlns:n0pred=”http://purl.org/ontology/peg#” rdf:resource=”http://purl.org/ontology/peg/framework#WellBeing”/></rdf:Description>
<rdf:Description rdf:about=”http://purl.org/ontology/peg/framework#Economy”><n0pred:isThemeOf xmlns:n0pred=”http://purl.org/ontology/peg#” rdf:resource=”http://purl.org/ontology/peg/framework#WellBeing”/></rdf:Description>
<rdf:Description rdf:about=”http://purl.org/ontology/peg/framework#Governance”><n0pred:isThemeOf xmlns:n0pred=”http://purl.org/ontology/peg#” rdf:resource=”http://purl.org/ontology/peg/framework#WellBeing”/></rdf:Description>
</rdf:RDF>
[/cc]

SPARQL Queries Restrictions

The structWSF SPARQL endpoint has some restrictions that have been introduced to make sure that the requesting users can only query the data to which they have access.

In structWSF, all permissions are attached to a dataset (a graph). Different users have different Create, Read, Update and Delete permissions on different datasets hosted on the same structWSF endpoint. Because of this core mechanism in structWSF, we had to make sure that these same restrictions were applied for the SPARQL endpoint. This means that different SPARQL clauses and usages are restricted.

This section covers these specific restrictions for a structWSF SPARQL endpoint.

Accessing Dataset Without Permissions

Let’s try to see what happens when someone tries to access a dataset to which he doesn’t have access. Consider this SPARQL query:

[cc lang=’text’ line_numbers=’false’ escaped=’true’]
PREFIX mypeg: <http://www.mypeg.ca/wsf/>
SELECT ?s ?p ?o FROM mypeg:
WHERE
{
?s ?p ?o .
}
[/cc]

Obviously, no user has a direct access to that dataset on the MyPeg instance:

[cc lang=’text’ line_numbers=’false’ escaped=’true’]
curl -H “Accept: application/rdf+n3” “http://www.mypeg.ca/ws/sparql/” -d “query= PREFIX%20mypeg%3A%20%3Chttp%3A%2F%2Fwww.mypeg.ca%2Fwsf%2F%3E%0ASELECT%20%3Fs%20%3Fp%20%3Fo%20FROM%20mypeg%3A%0AWHERE%0A%7B%0A%20%20%3Fs%20%3Fp%20%3Fo%20.%0A%7D%0A”
[/cc]

[cc lang=’xml’ line_numbers=’false’ escaped=’true’]

<error>
<id>WS-AUTH-VALIDATOR-303</id>
<webservice>/ws/auth/validator/</webservice>
<name>No access defined</name>
<description>No access defined for this requester IP , dataset and web service</description>
<debugInformation>No access defined for this requester IP (174.129.43.163), dataset (http://www.mypeg.ca/wsf/) and web service (http://www.mypeg.ca/wsf/ws/sparql/)</debugInformation>
<level>Warning</level>
</error>

[/cc]

So, even if a dataset exists in a triple store that exposes a SPARQL endpoint, not all users have access to all of these datasets. The access and permissions layer will restrict the access to them if need be.

If a FROM clause, or multiple FROM NAMED clauses are specified in the SPARQL query, the access layer will make sure that the user has access to all these datasets. If he doesn’t have access to one of them, then an error will be returned.

CONSTRUCT

The CONSTRUCT clause can be used against this SPARQL endpoint, but only if it doesn’t use any GRAPH clauses. However, we encourage users to use the method described in the section “Getting Records in Different Formats” since more formats can be requested, and more formats can easily be added in the future.

Here is an example of a CONSTRUCT query that uses a GRAPH clause:

[cc lang=’text’ line_numbers=’false’ escaped=’true’]
CONSTRUCT
{
?s ?p ?o
}
WHERE
{
graph <http://www.mypeg.ca/wsf/datasets/249/>
{
?s ?p ?o
}
}
[/cc]

[cc lang=’text’ line_numbers=’false’ escaped=’true’]
curl -H “Accept: application/rdf+xml” “http://www.mypeg.ca/ws/sparql/” -d ” query=CONSTRUCT%0A%7B%0A%20%20%3Fs%20%3Fp%20%3Fo%0A%7D%0AWHERE%20%0A%7B%20%0A%20%20graph%20%3C%20http%3A%2F%2Fwww.mypeg.ca%2Fwsf%2Fdatasets%2F249%2F%3E%0A%20%20%7B%0A%20%20%20%20%3Fs%20%3Fp%20%3Fo%0A%20%20%7D%0A%7D%0A”
[/cc]

[cc lang=’xml’ line_numbers=’false’ escaped=’true’]
<?xml version=”1.0″ encoding=”utf-8″?>
<error>
<id>WS-SPARQL-205</id>
<webservice>/ws/sparql/</webservice>
<name>GRAPH not permitted.</name>
<description>The SPARQL GRAPH clause is not permitted for this sparql endpoint. Please change your SPARQL query to specify the datasets you want to query with the FROM and FROM NAMED sparql clauses, or with the dataset parameter.</description>
<debugInformation></debugInformation>
<level>Warning</level>
</error>
[/cc]

As you can see, the endpoint will return a 205 error if a GRAPH clause is used within a CONSTRUCT statement.

GRAPH

As we saw above, no GRAPH clauses can be used in a SPARQL query. The reason is that we don’t want people to send SPARQL queries with GRAPH clauses that use variables. Otherwise, if we permitted GRAPH clauses to be used with variables, we couldn’t currently determine what triple comes from what dataset and so, we couldn’t ensure the access and permissions to that data.

However, in the future two improvements could be created to enable the usage of GRAPH clauses in SPARQL queries processed by structWSF:

  1. We could enable people to use GRAPH clauses that use direct IRI_REF references. That way, structWSF could easily check the permissions for these graphs (just like it does handle the FROM, FROM NAMED and DESCRIPTION clauses).
  2. We could enable the full usage of the GRAPH clause. However, we would have to modify the queries at the level of the endpoint to get the graph provenance of all the triples. Then the endpoint would have to analyze the provenance of each triple and only return the ones that the user has access to. This would inevitably slow down the query time to process the SPARQL request.

In the mean time, no GRAPH clauses can be used in any SPARQL query, and people should use the FROM and FROM NAMED clauses to get access to all the datasets they want from a particular endpoint.

SPARUL

No SPARQL/Update (SPARUL) queries can be sent via the structWSF SPARQL endpoint. All data modifications (records and/or dataset creation, updating and deleting) have to be performed by the Dataset and Record CRUD web service endpoints.

Conclusion

The structWSF SPARQL endpoint is a wrapper above a triple store’s SPARQL endpoint. It adds a permissions and access layer that is compatible with that used by other structWSF web services. This permission layer ensures that requesters only access the information they have access to within the triple store. Also, all of these access permissions are managed by the other structWSF web service endpoints, and can also be managed via the conStruct user interface.

The structWSF SPARQL endpoint also supports more resultset formats than are generally supported by mainstream triple stores. Also, the addition of new formats is made easier by using structWSF’s way to convert data in different formats.

Semantic Web, Structured Dynamics, OSF for Drupal, irON, OSF Web Services, OSF Widgets

Getting Data Out of MyPeg.ca using structWSF Endpoints

A few weeks ago I presented the new MyPeg.ca community indicators web portal for Winnipeg’s citizens. I explained how in MyPeg.ca we leverage Structured Dynamics’ semantic technologies stack (akaThe Semantic Muffin). Today’s blog post explains one facet of the project that shows how external agents (people, services, software, etc.) can interact with the system’s indicator datasets using the structWSF web service endpoints.Since this post focuses only on data export, I suggest you read the structWSF Web Services Tutorial for a complete overview of how the endpoints architecture works.

Merging Pipes

Two Main structWSF Characteristics: Accessibility & Management

structWSF is a set of 22 web service endpoints that lets you integrate data from different sources, manage that integrated data, and publish it via different communication channels such as web pages, software applications, etc.

Obviously, the main characteristic of this framework is that everything is a web service. This means that all functionality of the system can be accessed from anywhere on the Internet. However, this doesn’t mean that everything is open like a snack-bar. In fact, there are two levels of accessibility: (1) access to the web service endpoint’s URL, and (2) access to the content of datasets hosted on structWSF. Depending on the usecase, people could restrict the direct access to the web service endpoint(s) by properly configuring their web server, others could choose to let anyone access the endpoints, but would restrict the access to the dataset(s) hosted by structWSF. In case of MyPeg.ca, the sponsor chose to open the access to their web service endpoints and datasets.

Just by surfing on the MyPeg.ca portal, you are already leveraging these endpoints in multiple different ways. First, each time you generate a browse or a search Web page, you are telling the web server to send multiple queries to different endpoints; then the web page’s content will be populated with that information and presented to you. But, each time you click on an explorer node, your web browser is also sending queries to exactly the same web service endpoints. So, in one case a PHP script acts to query the endpoints; and, in other cases, a Flash Semantic Component does. Depending, all structWSF data can be accessed from quite different environments.

The other main characteristic of structWSF is that any kind of data can be imported in, and exported out, of the system. structWSF leverages RDF (Resource Description Framework) as the canonical data format that can be used to express any other formats. It is because of the usage of RDF that structWSF can act as an effective ETL (Extract, transform, load) system. Depending on the web service endpoint, the output formats currently supported by most of the endpoints are:

But the architecture of the web service endpoints can easily accommodate other formats if needed for a specific usecase.

Getting Data Out Of MyPeg.ca

Now, how can you get data out of MyPeg.ca? There are really two methods. This blog post discusses the CRUD: Read, Browse and Search web service endpoints. In my next blog post, I will focus on using the SPARQL web service endpoint to do the same.

All of the query examples in this blog post will use a tool called Curl to send the queries and to get back the resultsets. I encourage you to download and use that tool to test these endpoints and to gain a feeling for how it works. Also note that only the first record of each resultset is recorded below (of course, the actual results include all records).

Browse

The Browse web service endpoint is used to return lists of records. These records can also be filtered according to their provenance (dataset), type and the attributes that describe them. Now, let’s see how you can use this web service to get data out of MyPeg.ca.

First, there are three datasets available to the public:

  1. Well-being Indicators (http://www.mypeg.ca/wsf/datasets/258/)
  2. Stories (http://www.mypeg.ca/wsf/datasets/272/)
  3. PEG Framework (http://www.mypeg.ca/wsf/datasets/249/)

The resultsets can be serialized using one of these four different formats:

  • text/xml (structXML)
  • application/json (structXML in JSON)
  • application/rdf+xml (RDF/XML)
  • application/rdf+n3 (RDF/N3)

Note: if one of your desired formats is not directly available at the endpoint level, you can always use one of the converter web service endpoints such as: commON, irJSON or TSV/CSV.

Get the first 10 results of the Stories dataset in structXML

Query:

[cc lang=’text’ line_numbers=’false’]curl -H “Accept: text/xml” “http://www.mypeg.ca/ws/browse/” -d “attributes=all&types=all&datasets=http%3A%2F%2Fwww.mypeg.ca%2Fwsf%2Fdatasets%2F272%2F&items=10&page=0&inference=on&include_aggregates=true”[/cc]

StructXML resultset:

[cc lang=’xml’ line_numbers=’false’ escaped=’true’]

<?xml version=”1.0″ encoding=”utf-8″?>
<resultset>
<prefix entity=”owl” uri=”http://www.w3.org/2002/07/owl#”/>
<prefix entity=”rdf” uri=”http://www.w3.org/1999/02/22-rdf-syntax-ns#”/>
<prefix entity=”rdfs” uri=”http://www.w3.org/2000/01/rdf-schema#”/>
<prefix entity=”wsf” uri=”http://purl.org/ontology/wsf#”/>
<subject type=”http://purl.org/ontology/muni#Story” uri=”http://www.mypeg.ca/wsf/datasets/272/resource/AgeOpportunity”>
<predicate type=”http://purl.org/dc/terms/isPartOf”>
<object type=”http://rdfs.org/ns/void#Dataset” uri=”http://www.mypeg.ca/wsf/datasets/272/”/>
</predicate>
<predicate type=”http://purl.org/ontology/iron#prefLabel”>
<object type=”rdfs:Literal”>Age &amp; Opportunity</object>
</predicate>
<predicate type=”http://purl.org/dc/terms/created”>
<object type=”rdfs:Literal”>2010-10-28T19:38:58+00:00</object>
</predicate>
<predicate type=”http://purl.org/ontology/bibo/abstract”>
<object type=”rdfs:Literal”>Amanda Macrae, Deborah Lorteau and Stacey Miller work for Age and Opportunity.
The majority of clients are older adults living at lower socio economic status. When addressing the housing issue they say, “In a nutshell, it’s dire.” There is simply not enou…</object>
</predicate>
<predicate type=”http://purl.org/ontology/peg#interviewee”>
<object type=”rdfs:Literal”>Amanda Macrae, Deborah Lorteau, Stacey Miller</object>
</predicate>
<predicate type=”http://purl.org/ontology/peg#interviewer”>
<object type=”rdfs:Literal”>Molly Johnson</object>
</predicate>
<predicate type=”http://purl.org/ontology/peg#storyRelatedAgencyProgram”>
<object type=”rdfs:Literal”>Age &amp; Opportunity</object>
</predicate>
<predicate type=”http://purl.org/ontology/sco#storyAnnotatedTextUri”>
<object>http://www.mypeg.ca/scones/AgeOpportunity.xml</object>
</predicate>
<predicate type=”http://purl.org/ontology/sco#storyTextUri”>
<object type=”rdfs:Literal”>http://www.mypeg.ca/scones/AgeOpportunity.txt</object>
</predicate>
</subject>
</resultset>

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Get the 10 first results from all datasets that are records of type Neighborhoods in RDF/XML

Query:

[cc lang=’text’ line_numbers=’false’]curl -H “Accept: application/rdf+xml ” “http://www.mypeg.ca/ws/browse/” -d “attributes=all& type=http%3A%2F%2Fpurl.org%2Fontology%2Fpeg%23Neighborhood &datasets=all&items=10&page=0&inference=on&include_aggregates=true”[/cc]

RDF/XML resultset:

[cc lang=’xml’ line_numbers=’false’ escaped=’true’]

<?xml version=”1.0″?>
<rdf:RDF  xmlns:owl=”http://www.w3.org/2002/07/owl#” xmlns:rdf=”http://www.w3.org/1999/02/22-rdf-syntax-ns#” xmlns:rdfs=”http://www.w3.org/2000/01/rdf-schema#” xmlns:wsf=”http://purl.org/ontology/wsf#” xmlns:ns0=”http://purl.org/ontology/peg#” xmlns:ns1=”http://purl.org/dc/terms/” xmlns:ns2=”http://purl.org/ontology/iron#” xmlns:ns3=”” xmlns:ns4=”http://purl.org/dc/elements/1.1/” xmlns:ns5=”http://purl.org/ontology/aggregate#”>

<ns0:Component rdf:about=”http://purl.org/ontology/peg/framework#Safety”>
<ns1:isPartOf rdf:resource=”http://www.mypeg.ca/wsf/datasets/249/” />
<ns2:prefLabel>Safety</ns2:prefLabel>
<ns2:altLabel>safety</ns2:altLabel>
<ns3:>safety</ns3:>
<ns4:description>Safety is the state of being “safe”, the condition of being protected against physical, social, spiritual, financial, political, emotional, occupational, psychological, educational or other types or consequences of failure, damage, error, accidents, harm or any other event which could be considered non-desirable.</ns4:description>
<rdfs:comment>Includes the idea of safety prevention</rdfs:comment>
<rdfs:seeAlso>http://en.wikipedia.org/wiki/Safety</rdfs:seeAlso>
<ns0:hasIndicator rdf:resource=”http://purl.org/ontology/peg/framework#HouseholdIncome” />
<ns0:hasIndicator rdf:resource=”http://purl.org/ontology/peg/framework#LowIncomeCutOffAfterTax” />
<ns0:hasIndicator rdf:resource=”http://purl.org/ontology/peg/framework#MarketBasketMeasure” />
<ns0:hasIndicator rdf:resource=”http://purl.org/ontology/peg/framework#ParticipationInSportsAndRecreation” />
<ns0:hasIndicator rdf:resource=”http://purl.org/ontology/peg/framework#MaternalSocialIsolation” />
<ns0:hasIndicator rdf:resource=”http://purl.org/ontology/peg/framework#PersonalSafety” />
<ns0:hasIndicator rdf:resource=”http://purl.org/ontology/peg/framework#EarlyDevelopmentInstrument” />
<ns0:hasIndicator rdf:resource=”http://purl.org/ontology/peg/framework#HighSchoolGraduationRate” />
<ns0:hasIndicator rdf:resource=”http://purl.org/ontology/peg/framework#LongTermUnemployment” />
<ns0:hasIndicator rdf:resource=”http://purl.org/ontology/peg/framework#TeenageBirths” />
<ns0:isComponentOf rdf:resource=”http://purl.org/ontology/peg/framework#BasicNeeds” />
<ns0:isComponentOf rdf:resource=”http://purl.org/ontology/peg/framework#Poverty” />
</ns0:Component>
</rdf:RDF>

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Search

The Search web service endpoint is also used to return lists of records. These records should match a search string and can also be filtered according to their provenance (dataset), type and the attributes that describe them.

The same mime types and datasets as the ones for the Browse web service are available for the Search endpoint.

Searching for records with the keyword “poverty” and get resultsets in RDF/N3

Query:

[cc lang=’text’ line_numbers=’false’]curl -H “Accept: application/rdf+n3” “http://www.mypeg.ca/ws/search/” -d “query=poverty&datasets=all&items=10&page=0&inference=on&include_aggregates=true”[/cc]

RDF/N3 resultset:

[cc lang=’text’ line_numbers=’false’ escaped=’true’]

@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix wsf: <http://purl.org/ontology/wsf#> .

<http://purl.org/ontology/peg/framework#Poverty> a <http://purl.org/ontology/peg#CrossCuttingIssue> ;
<http://purl.org/dc/terms/isPartOf> <http://www.mypeg.ca/wsf/datasets/249/> ;
<http://purl.org/ontology/iron#prefLabel> “””Poverty””” ;
<http://purl.org/dc/elements/1.1/description> “””Poverty is not having the sufficient resources, capabilities, choices, security and power necessary to enjoy an adequate standard of living.  Poverty includes much more than a lack of money.  It includes being excluded from ordinary living patterns, customs and activities.  Consequently, people living in poverty are often unable to participate fully in their communities or to reach their full potential.””” ;
<http://www.w3.org/2000/01/rdf-schema#seeAlso> “””http://en.wikipedia.org/wiki/Poverty””” .

[/cc]

CRUD: Read

The Browse and Search web service endpoints are really used to find lists of records according to some provided criteria. However, the complete description of these records is not returned by these endpoints, but only the information necessary to create the proper list to display to users in a user interface. So, to get the complete description of a record (or multiples thereof), you have to use the CRUD: Read web service endpoint. Also, sometimes you may get a reference to a record hosted on a structWSF node, then CRUD: Read is the way to get its full description.

Get the full description of the Ida story in irJSON

Query:

[cc lang=’text’ line_numbers=’false’]curl -H “Accept: application/iron+json” “http://www.mypeg.ca/ws/crud/read/?uri=http%3A%2F%2Fwww.mypeg.ca%2Fwsf%2Fdatasets%2F272%2Fresource%2FIda&dataset=http%3A%2F%2Fwww.mypeg.ca%2Fwsf%2Fdatasets%2F272%2F&include_reification=true&include_linksback=false[/cc]

irJSON resulset:

[cc lang=’javascript’ line_numbers=’false’ escaped=’true’]

{
“dataset”: {
“linkage”: [
{
“linkedType”: “application/rdf+xml”,
“attributeList”: {
“created”: {
“mapTo”: “http://purl.org/dc/terms/created”
},
“isAbout”: {
“mapTo”: “http://umbel.org/umbel#isAbout”
},
“prefLabel”: {
“mapTo”: “http://purl.org/ontology/iron#prefLabel”
},
“interviewee”: {
“mapTo”: “http://purl.org/ontology/peg#interviewee”
},
“interviewer”: {
“mapTo”: “http://purl.org/ontology/peg#interviewer”
},
“abstract”: {
“mapTo”: “http://purl.org/ontology/bibo/abstract”
},
“storyVideoAudio”: {
“mapTo”: “http://purl.org/ontology/peg#storyVideoAudio”
},
“storyAnnotatedTextUri”: {
“mapTo”: “http://purl.org/ontology/sco#storyAnnotatedTextUri”
},
“storyTextUri”: {
“mapTo”: “http://purl.org/ontology/sco#storyTextUri”
}
},
“typeList”: {
“Story”: {
“mapTo”: “http://purl.org/ontology/muni#Story”
}
}
}
]},
“recordList”: [
{
“id”: “http://www.mypeg.ca/wsf/datasets/272/resource/Ida”,
“type”: “Story”,
“created”: “2010-10-28T18:11:27+00:00”,
“isAbout”: [
{
“ref”: “@@http://purl.org/ontology/peg/framework#EducationAndLearning”
},
{
“ref”: “@@http://purl.org/ontology/peg/framework#Health”
},
{
“ref”: “@@http://purl.org/ontology/peg/framework#Program”
},
{
“ref”: “@@http://purl.org/ontology/peg/framework#Income”
},
{
“ref”: “@@http://purl.org/ontology/peg/framework#Poverty”
}     ],
“prefLabel”: “Ida”,
“interviewee”: “Ida”,
“interviewer”: “Christa Rust”,
“abstract”: “‘Poverty is earning just enough to get by; never having money for extras.’\n\nIda is the mother of two grown children, eight years apart.  She lives in a small bachelor suite, which costs her $428 per month, or 62% of her income.  She volunteers twice a we…”,
“storyVideoAudio”: “http://www.youtube.com/v/0zIqtYhiHfM”,
“storyAnnotatedTextUri”: “http://www.mypeg.ca/scones/Ida.xml”,
“storyTextUri”: “http://www.mypeg.ca/scones/Ida.txt”
}
]
}

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Get Well-Being record description with linkbacks in RDF+N3

The characteristic of this query is that I enabled the “include_linksback” parameter. This returns a reference to all the records, in the datasets hosted on the structWSF node, that refers to that target record.

Query:

[cc lang=’text’ line_numbers=’false’]curl -H “Accept: application/rdf+n3” “http://www.mypeg.ca/ws/crud/read/?uri=http%3A%2F%2Fpurl.org%2Fontology%2Fpeg%2Fframework%23WellBeing&datast=http%3A%2F%2Fwww.mypeg.ca%2Fwsf%2Fdatasets%2F249%2F&registered_ip=self%3A%3A0&include_reification=true&include_linksback=true”[/cc]

RDF+N3 resultset:

[cc lang=’text’ line_numbers=’false’ escaped=’true’]

@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .

<http://purl.org/ontology/peg/framework#WellBeing> a <http://purl.org/ontology/peg/framework#WellBeing> ;
<http://purl.org/ontology/iron#prefLabel> “””Well-being””” ;
<http://purl.org/dc/elements/1.1/description> “””Well-being refers to the general quality of life experienced by individuals and communities. The elements of wellbeing include: the ability to meet basic needs, the economy, health, the built environment, governance, education and learning, the natural environment, and social vitality.””” ;
<http://purl.org/ontology/sco#displayComponent> <http://purl.org/ontology/sco#sRelationBrowser> .

<http://purl.org/ontology/peg/framework#WellBeing> a <http://www.w3.org/2002/07/owl#Thing> ;
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://purl.org/ontology/peg/framework#WellBeing> .

<http://purl.org/ontology/peg/framework#Economy> a <http://www.w3.org/2002/07/owl#Thing> ;
<http://purl.org/ontology/peg#isThemeOf> <http://purl.org/ontology/peg/framework#WellBeing> .

<http://purl.org/ontology/peg/framework#Governance> a <http://www.w3.org/2002/07/owl#Thing> ;
<http://purl.org/ontology/peg#isThemeOf> <http://purl.org/ontology/peg/framework#WellBeing> .

<http://purl.org/ontology/peg/framework#BuiltEnvironment> a <http://www.w3.org/2002/07/owl#Thing> ;
<http://purl.org/ontology/peg#isThemeOf> <http://purl.org/ontology/peg/framework#WellBeing> .

<http://purl.org/ontology/peg/framework#NaturalEnvironment> a <http://www.w3.org/2002/07/owl#Thing> ;
<http://purl.org/ontology/peg#isThemeOf> <http://purl.org/ontology/peg/framework#WellBeing> .

<http://purl.org/ontology/peg/framework#SocialVitality> a <http://www.w3.org/2002/07/owl#Thing> ;
<http://purl.org/ontology/peg#isThemeOf> <http://purl.org/ontology/peg/framework#WellBeing> .

<http://purl.org/ontology/peg/framework#BasicNeeds> a <http://www.w3.org/2002/07/owl#Thing> ;
<http://purl.org/ontology/peg#isThemeOf> <http://purl.org/ontology/peg/framework#WellBeing> .

<http://purl.org/ontology/peg/framework#EducationAndLearning> a <http://www.w3.org/2002/07/owl#Thing> ;
<http://purl.org/ontology/peg#isThemeOf> <http://purl.org/ontology/peg/framework#WellBeing> .

<http://purl.org/ontology/peg/framework#Health> a <http://www.w3.org/2002/07/owl#Thing> ;
<http://purl.org/ontology/peg#isThemeOf> <http://purl.org/ontology/peg/framework#WellBeing> .

[/cc]

General Endpoint Parameters

The general parameters available for each of these web services is provided in their respective TechWiki documentation. For that detailed information, see the Browse, Search, or CRUD: Read articles.

Conclusion

As you can see, agents can get different kinds of data from the MyPeg.ca portal by querying a set of web service endpoints. This is one way to get data out of the system. These data can then be accessed for indexing in other systems, for direct use, or for dynamic applications like browsing the nodes in the explorer.

This is one of the ways to get data out of the system. A user can also export that same information from the Export features on the Browse, Search and Record View pages. Also, other methods will be explained in the next blog posts from this MyPeg.ca series.

All in all, this shows how effective structWSF can be to integrate, manage and publish a wide range of data in different data formats. It also shows how completely different parts of your software architecture can leverage your information, the way you want, from anywhere on the Internet.

Semantic Web, Structured Dynamics, UMBEL, Ping the Semantic Web

A New Home for UMBEL Web Services

umbel_wsEight months ago we announced the dissolution of Zitgist LLC. This event led to the creation of a sandbox to keep alive all the online assets of the company. Since this sandbox server was not owned by Structured Dynamics, it was becoming hard for us to update UMBEL and its online services. It is why we took the time to move the services back on to our new servers.

A New Home

sd_logo_260Structured Dynamics LLC now hosts a new version for the UMBEL Web services. From the main menu at the SD Web site you can access these services under the “umbel ws” menu option (you can also bookmark the Web services site at umbel.structureddynamics.com or ws.umbel.org.)

This move of UMBEL’s Web services to a new home will make the future upgrade of UMBEL easier, and this will make the maintenance of the Web services endpoints easier as well. With this move, I am pleased to announce the release of five initial Web services and one visualization tool:

Lookup Web Services:

Inference Engine Web Services:

SPARQL endpoint Web Service:

Visual Tool:

Note that the visual tool is using Moritz Stefaner’s Relation Browser.


Ping the Semantic Web

ptswlogo160.gifAdditionally, the Ping the Semantic Web RDF pinging service is now the property of OpenLink Software Inc. OpenLink is now hosting, maintaining and developing the service.

Semantic Web, Zitgist, UMBEL

UMBEL Web Services Endpoints Released

After some delay, we are pleased to finally release the UMBEL Web services endpoints to the public. We have re-organized the Web services we introduced three months ago to add coherency and flexibility to the model.

The goal remains the same, but with a different flavor: these tools let ontologists and Web developers search, discover and use the UMBEL subject concept and named entity structures. The added flavor is that these Web services now fully embrace the HTTP 1.1 protocol and are provided via a series of well established data and serialization formats.

We now have RESTful Web services to add to our RESTful linked data. Pretty cool combination!

We are introducing two kinds of Web services: (1) atomic Web services and (2) compound Web services. An atomic Web service only performs one action: It takes some inputs and then outputs a resultset of the action. A compound Web service takes multiple atomic Web services, plugs them together in a pipeline model, and then takes some inputs and outputs a resultset arising from the compound action.

The communication between each of these Web service instances and the external World is the same: communication is governed by the HTTP 1.1 protocol. HTTP is generally RESTful and used to establish the communication, to determine mime type and serialization, to get inputs, to return status of the communication and possible errors, and to send back the resultset of the computation of the Web service.

That way, we can easily, within hours, programmatically pipeline these atomic Web services together to create new Web services. We can integrate external Web services endpoints into the same pipeline without modifying anything to the architecture. Status, errors and resultsets are propagated along the line, directly to the data consumer. This is the flexibility part of the story.

Now, how cool is that?

Overview of the UMBEL Web Services Endpoints

We are today releasing a couple of these atomic and compound Web service endpoints to the public, but others will follow in the coming weeks and months. Four families of Web services have been released that total seven Web service endpoints:

If you don’t know what UMBEL is, I would suggest you read a background information page that talks about the project.

The most important reading related to this blog post is the API philosophy documentation page that talks about the details of the design of this Web services architecture.

For Web developers that want to integrate these Web services endpoints within their application, an API documentation page explains how to communicate with these endpoints for each of the services.

Example of an Atomic Web Service

The Inference: Lister Web service is a good example of an atomic Web service. It takes a subject concept URI as the input and outputs a series of super-class-of, sub-class-of or equivalent-class-of classes for that concept. As an atomic service it does one thing and one thing only: Inferring relationships of a given subject concept URI.

Example of a Compound Web Service

The Reporter: Named Entity Web service is a good example of a compound Web service. This Web service displays full of information about a UMBEL named entity URI. However, not all the information returned by this Web service is directly computed by it. In fact, the information about broader and equivalent classes and subject concepts come from the Inference: Lister Web service. Results coming from this Web service are immediately integrated in the Reporter’s resultset. This is easily done considering that they share the same communication language (HTTP 1.1) and the same data and serialization formats (XML, RDF+XML and RDF+N3). This flexibility is priceless to quickly create resourceful compound Web services.

Conclusion

After some months to get the design right, we have finally released some of the UMBEL Web services to the public. These Web services can easily be integrated in current software architectures to leverage UMBEL’s vision of the World. The architecture underlying what we have released today will help to easily integrate UMBEL’s principles and concepts within new and existing projects. This will ultimately help people to quickly react to the changing World of needs and expectations of data users and consumers.

I hope you will enjoy using these new Web services, which Zitgist is freely hosting. The data you get from the Web service is open data and can be used freely with attribution.

Please do report any issues you may encounter. We also welcome any advice or suggestions that you would care to provide to enhance the overall system.