A Curious Animal

Some days ago I saw this post, from Ron Lake's blog, in the Planet Geospatial.

As Ron says, ...In common parlance, and in land surveying, a datum is a reference point or reference surface.  Sometimes this is also interpreted as the zero point for a measurement... but ...provide a poor basis for generalization...

Datum – What’s in a name?

Enjoy it !

Many of us knows the origin of the microchips but probably don't know about its fabrication process.

This post points to a very nice PCPlus maginze which shows how this "complex components are made from nothing more glamorous than sand".

Today I need to install an Oracle instance to make some tests. No benchmarks, no cluster, nothing complicated, so I decide to create a VirtualBox Ubuntu image and install Oracle XE on it.

I'll try to sumarize the steps I follow.

1. Create the VirtualBox Ubuntu image. I have prepared a 10Gb disk file and install Ubuntu from the distro ISO file. You must take into account that Oracle needs a swap file greather than 500Mb (aprox.). If for some reason (like me) you create the swap partition less than 500Mb you can follow next workaround to solve the problem:
   • Restart the virtual machine, configuring the CD-ROM to load the Ubuntu ISO file (it is a LiveCD).
   • Execute the gparted program and resize your swap partition to take the right size.
2. Once you have the virtual machine you need to install Oracle. An easy option is to configure the debian/ubuntu repository that Oracle offers.
   • Add the next repository to your apt sources:

     deb http://oss.oracle.com/debian unstable main non-free.

   • Update the repository db and install Oracle XE:

     # wget http://oss.oracle.com/el4/RPM-GPG-KEY-oracle  -O- | sudo apt-key add - 
     # apt-get update
     # apt-get install oracle-xe oracle-xe-client

3. After installation was done, don't forget to execute:

   # /etc/init.d/oracle-xe configure

Now you have installed an instance of Oracle XE ready to work.

Links

• Installing Oracle Database XE on Debian, Ubuntu, and Kubuntu
• Installing Oracle 11gR1 on Ubuntu 8.10 Intrepid Ibex

You have installed the PostgreSQL and PostGIS pacakges that Ubuntu easely provides but... you are unable to create your GIS database. Maybe you need the next:

# log in to the database template1:

psql template1

# issue command to create new database:

create database template_postgis with template = template1;

# update pg_database table to indicate that new database is a template

UPDATE pg_database SET datistemplate = TRUE where datname = 'template_postgis';

# connect to new database

\c template_postgis

# add PostGIS extensions and grant access to everyone to spatial tables.

CREATE LANGUAGE plpgsql ;

\i /usr/share/postgresql-8.3-postgis/lwpostgis.sql;

\i /usr/share/postgresql-8.3-postgis/spatial_ref_sys.sql;

GRANT ALL ON geometry_columns TO PUBLIC;

GRANT ALL ON spatial_ref_sys TO PUBLIC;

# prevent further changes to this database

VACUUM FREEZE;

Via: http://blog.ralreegorganon.com

Here are six little things you can do to hold disciplined with your work, or at least helps to you to be a bit more disciplined.

It can be very helpful if you work as a freelance and sometimes you feel your productivite goes down.

1. Forgive yourself. You aren’t perfect.
2. Realize that discipline is an illusion. While discipline is a common concept, it doesn’t actually exist.
3. Focus on motivation. When things get tough, remind yourself of your motivation.
4. Make it easy.
5. Focus on enjoyment. Focus on the enjoyable aspect of your work. Open your mind.
6. Repeat.

Via: 6 Small Things You Can Do When You Lack Discipline.

Every body know about the Chuck Norris facts, but as you may think, Cuchk is much more than you or me, he is what he wants to be. So here I present some facts of Chuck Norris about Java, yes he knows about everything.

Some of my favourites facts are:

• Chuck Norris extends God.
• Chuck Norris can divide by 0!
• If you get a ChuckNorrisException you’ll probably die.

Found at: http://www.ovisual.com

Some days ago I read a post related to the citygml4j project. As its web page says:

citygml4j is a Java class library and API for facilitating work with the City Geography Markup Language (CityGML). citygml4j makes it easy to read, process, and write CityGML datasets, and to develop CityGML-aware software applications.

A couple of days ago I downloaded the binary package and try to execute some samples. Unfortunately it was compiled using Java6 and I was using Java.5 because I need it for my current project.

I wrote an email to Claus Nagel, the project manager,  talking about my "problem" and (wow) a couple of hours after, Claus has published a new binary package ready to use with Java1.5.

I only have congratulation words for you Claus ;)

JPA is the ORM specification which allows us to work in the same way independently of the ORM underline engine: hibernate, toplink, JDO, etc.

The most important concept is the entity, but around it there are a lot of other concepts like PersistenceContext, PersistenceUnits, EntityManager, etc.

Here is a brief summary of this concepts and the actions you can make over an entity:

• A PersistenceContext is a set of entity instances.
• A EntityManager is associated with a PersistenceContext and is used to create and remove persistent entity instances, to find entities by their primary key, and to query over entities.

You can think about the PersistenceContext as a kind of cache of the database. The basic actions you can make over an entity are: