29 June 2007

Installing OracleXE

We have been adding support for Oracle into SDB. As part of that, I installed Oracle XE ("Oracle Database 10g Express Edition") on my WindowsXP machine at work, which is part of a Windows domain.

It didn't go smoothly. I hope these notes help someone else trying to do the same thing.


  • Install when logged in as administrator (NOT a domain user, even if in group Administrators).
  • In order to use the command line SQL interface, you need to change SQLNET.ORA from (NTS) to (none)


The Oracle installation instructions say to log in with administrative privileges and be attached to the domain.

The installation proceeded with no errors, and the 5 Windows services start up OK. But I found that I could not connect to the database web-based admin interface.

An additional symptom was that I can't change my domain password, nor create Windows local user accounts. In both cases, the error was that the password does not meet the requirements on characters and length. HP has tighter guidelines than the default for passwords but why installation of OracleXE broke a part of WindowsXP, I don't understand. After uninstalling OracleXE, I could change my password and create local user accounts as usual.

There are lots of articles about not being about to contact the database home page but only a few were related to the situation I had: this one was most useful (that link is into the OracleXE forum which is not publicly readable - you have to register first).

A way to see if your installation has been affected is to see if there is a file server\dbs\SPFILEXE.ORA. If not, the installation is probably broken.

Logging in as the local administrator account, uninstalling, reinstalling got an installation where I could get to the database home page and administer the database. I guess any local user account in group Administarors would work.

But sqlplus.exe still didn't work. (The error is "ORA-12638: Credential retrieval failed"). Following that thread again, I changed SQLNET.ORA to  SQLNET.AUTHENTICATION_SERVICES = (none)  and could connect to the database from the SQL command prompt.

Afterwards ...

Installing on Windows XP/Home worked fine but that is not a domained machine.

And after all that, the SDB SPARQL test suite runs perfectly with OracleXE.

22 June 2007

Joseki 3.1

New version of Joseki released, primarily to package together all the updated jars files for Jena and ARQ that Joseki uses. At the same time, other jars have been upgraded so there are jar naming changes.

Joseki 3.1 download

10 June 2007

SPARQL Papers at ESWC 2007

There were 3 papers that particularly caught my SPARQL-driven attention at ESWC2007.

SPARQLeR: Extended Sparql for Semantic Association Discovery
Krys J. Kochut, Maciej Janik

This describes an extension to SPARQL for path variables. A path is a regular expression of properties but in addition the paper describes the need for reverse properties and constraints on paths (like length).

See also: PSPARQL: http://psparql.inrialpes.fr/

Minimal Deductive Systems for RDF
Sergio Muñoz, Jorge Pérez and Claudio Gutierrez.

This is a proposal for reduced RDFS with just rdfs:domain, rdfs:range, rdfs:subClassOf, rdfs:subPropertyOf and rdf:type.

This results in (on page 8) a small set of rules that have to be applied to the data but there is no core vocabulary. The rules can be applied to a streaming data stream, if the RDFS schema is known, because each rule only refers to at most one data triple.

There are no containers, which may be inconvenient, but that might more usefully be covered by not using typing, but having a different property just to match these syntactic constructs. That removes the container vocabulary from interacting with the application vocabulary.

A colleague here, Nipun Bhatia, has been working on streaming checking and rule application based on extending Eyeball. Nipun even adds cardinality validation by preprocessing the data to get the triples in subject order. Unix sort(1) is quite capable of sorting very large N-triples files in sensible amounts of time.

Semantic Process Retrieval with iSPARQL
Christoph Kiefer, Abraham Bernstein, Hong Joo Lee, Mark Klein and Markus Stocker.

((Non) interest declaration: Markus is now spending a few months working with us in Bristol - this work was done before that.)

The core of this paper is an example where statistical techniques beats logic. There is a strong message to us all here - don't think logic and perfect organization is necessarily the best solution to actual problems.

As part of this work, but not the main argument of the paper, they created iSPARQL (i=inprecise) which is an embedding of access to similarity metrics inside standard SPARQL without syntax changes. They use property functions (they are using ARQ but the principle is quite general) to access the similarity engine.

The idea of embedding some index or other functionality that can provide bindings of variables for some expression seems like a general extension technique for SPARQL. LARQ provides free-texting matching, using Lucene to do matching, and can include all the Lucene loose matching