Home » Bluespeak

I was recently asked about the SPARQL support in Sparql Droid and whether it could serve as a way for other Android applications to execute SPARQL queries against remote data sources.  It could be used in this way but there is a simpler alternative I’d like to discuss here.

On the Android platform it is actually quite easy to execute SPARQL against remote SPARQL endpoints, RDF data and local models.  The heavy lifting is handled by Androjena’s ARQoid, an Android-centric port of HP’s Jena ARQ engine.

Both engines (the original and the port) do a great job of simplifying the execution of SPARQL queries and consumption of the resulting data.  In this post I’ll go through a simple example of using ARQoid.  Note that all the code being shown here is available for download.  This post is based specifically on the queryRemoteSparqlEndpoint() method in the com.monead.androjena.demo.arqoid.SparqlExamples class.

Thursday December 01, 2011 | By David Read

As I release my 3rd Alpha-version of Sparql Droid I thought I’d document a few lessons learned and open items as I work with the Android environment.  Some of my constraints are based on targeting smart phones rather than tablets, but the lessons learned around development environments, screen layouts, and memory management are valuable.

I’ll start on the development side.  I use Eclipse and the android development plugin is very helpful. It greatly streamlines the development process.  Principally, it automates the generation of the resources from the source files.  These resources, such as screen layouts and menus, require a conversion step after being edited.  The automation, though, comes at a price.

Tuesday July 12, 2011 | By David Read

The semantic technology concepts that comprise what is generally called the semantic web involve paradigm shifts in the ways that we represent data, organize information and compute results. Such shifts create opportunities and present challenges. The opportunities include easier correlation of decentralized information, flexible data relationships and reduced data storage entropy. The challenges include new data management technology, new syntaxes, and a new separation of data and its relationships.

I am a strong advocate of leveraging semantic technology. I believe that this new paradigms provide a more flexible basis for our journey to create meaningful, efficient and effective business automation solutions. However, one challenge that differentiates leveraging semantic technology from more common technology (such as relational databases) is the lack of mature tools supporting a business system infrastructure.

It will take a while for solid solutions to appear. Support for mainstream capabilities such as reporting, BI, workflow, application design and development that all leverage semantic technology are missing or weak at best. Again, this is an opportunity and a challenge. For those who enjoy creating computer software it presents a new world of possibilities. For those looking to leverage mature solutions in order to advance their business vision it will take investment and patience.

Friday June 24, 2011 | By David Read

Being a consumer of semantic data I thought creating a SPARQL endpoint would be an interesting exercise.  It would require having some data to publish as well as working with a SPARQL library.  For data, I chose a set of mileage information that I have been collecting on my cars for the last 5 years.  For technology, I decided to use the Joseki SPARQL Server, since I was already using Jena.

For those who want to skip the “how” and see the result, the SPARQL endpoint along with sample queries and a link to the ontology and data is at: http://monead.com/semantic/query.html

The first step in this project was to convert my mileage spreadsheets into triples.  I looked briefly for an existing ontology in the automobile domain but didn’t find anything I could use.  I created an ontology that would reflect my approach to recording automobile mileage data.  My data  records the miles traveled between fill-ups as well as the number of gallons used.  I also record the car’s claimed MPG as well as calculating the actual MPG.

The ontology reflects this perspective of calculating the MPG at each fill-up.  This means that the purchase of gas is abstracted to a class with information such as miles traveled, gallons used and date of purchase as attributes.  I abstracted the gas station and location as classes, assuming that over time I might be able to flesh these out (in the spreadsheet I record the name of the station and the town/state).

A trivial Java program converts my spreadsheet (CSV) data into triples matching the ontology.  I then run the ontology and data through Pellet to derive any additional triples from the ontology.  The entire ontology and current data are available at http://monead.com/semantic/data/HybridMileageOntologyAll.Inferenced.xml.

It turns out that the ontology creation and data conversion were the easy parts of this project.  Getting Joseki to work as desired took some time, mostly because I couldn’t find much documentation for deploying it as a servlet rather than using its standalone server feature.  I eventually downloaded the Joseki source in order to understand what was going wrong.  The principle issue is that Joseki doesn’t seem to understand the WAR environment and relative paths (e.g. relative to its own WAR).

I had two major PATH issues: 1) getting Joseki to find its configuration (joseki-config.ttl); and 2) getting Joseki to find the triple store (in this case a flat file).

Monday November 29, 2010 | By David Read

My last two days at JavaOne 2010 included some interesting sessions as well as spending some time in the pavilion.  I’ll mention a few of the session topics that I found interesting as well as some of the products that I intend to check out.

I attended a session on creating a web architecture focused on high-performance with low-bandwidth.  The speaker was tasked with designing a web-based framework for the government of Ethiopia.  He discussed the challenges that are presented by that country’s infrastructure – consider network speed on the order of 5Kbps between sites.  He also had to work with an IT group that, although educated and intelligent, did not have a lot of depth beyond working with an Oracle database’s features.

His solution allows developers to create fully functional web applications that keep exchanged payloads under 10K.  Although I understand the logic of the approach in this case, I’m not sure the technique would be practical in situations without such severe bandwidth and skill set limitations.

A basic theme during his talk was to keep the data and logic tightly co-located.  In his case it is all located in the database (PL/SQL) but he agreed that it could all be in the application tier (e.g. NoSQL).  I’m not convinced that this is a good approach to creating maintainable high-volume applications.  It could be that the domain of business applications and business verticals in which I often find myself differ from the use cases that are common to developers promoting the removal of tiers from the stack (whether removing the DB server or the mid-tier logic server).

One part of his approach with which I absolutely concur is to push processing onto the client. The use of the client’s CPU seems common sense to me.  The work is around balancing that with security and bandwidth.  However, it can be done and I believe we will continue to find more effective ways to leverage all that computer power.

Sunday September 26, 2010 | By David Read

I’ve been at Oracle’s combined JavaOne and OpenWorld events for two days.  I am here as both an attendee, learning from a variety of experts, and as a speaker.  Of course this is the first JavaOne since Oracle acquired Sun.  I have been to several JavaOne conferences over the years so I was curious how the event might be different.

One of the first changes that I’ve noticed is that due to the co-location of these two large conferences the venue is very different than when Sun ran JavaOne as a standalone event.  The time between sessions is a full half hour, probably due to the fact that you may find yourself going between venues that are several blocks apart.  I used to think that having getting from Moscone North the Moscone South took a while.   Now I’m walking from the Moscone center to a variety of hotels and back again.  Perhaps this is actually a health regime for programmers!

The new session pre-registration system is interesting. I don’t know if this system has been routine with Oracle’s other conferences but it is new to JavaOne.  Attendees go on-line and pre-register for the sessions they want to attend.  When you show up at the session your badge is scanned.  If you had registered you are allowed in.  If you didn’t preregister and the session is full you have to wait outside the room to see if anyone who registered fails to show up.

I think I like the system, with the assumption that they would stop people from entering when the room was full.  At previous conferences it seemed like popular sessions would just be standing room only, but that was probably a violation of fire codes.  The big advantage of this approach is that it reduces the likelihood of your investing the time to walk to the venue only to find out you can’t get in.  As long as you arranged your schedule on-line and you show up on-time, you’re guaranteed a seat.

Enough about new processes.  After all, I came here to co-present a session and to learn from a variety of others.

Paul Evans and I spoke on the topic of web services and their use with a rules engine. Specifically we were using JAX-WS and Drools.  We also threw in jUDDI to show the value of service location decoupling.  The session was well attended (essentially the room was full) and seemed to keep the attendees’ attention.  We had some good follow-up conversations regarding aspects of the presentation that caught people’s interest, which is always rewarding. The source code for the demonstration program is located at http://bit.ly/blueslate-javaone2010.

Since I am a speaker I have access to both JavaOne and OpenWorld sessions.  I took advantage of that by attending several OpenWorld sessions in addition to a bunch of JavaOne talks.

Wednesday September 22, 2010 | By David Read