{ Make this readable }

Sunday, June 21, 2009

Sanborn-Skyline County Park (this time for real)

This is another nice park that intersects the fabled Skyline trail. The entrance is on the way to Big Basin and very easy to miss which I did a few weeks ago. So, this time I made the correct turn and made it about 2.5 hours before what looked like a Wedding party about to start. There must've been about 25 cars lined up at the gate that I saw while heading back home.

Well, the park itself is quite big and very nice. I wouldn't mind attending a party on the lush lawns and cozy picnic spots. There's a $6 parking fee. It's manned so, you don't have to worry about exact change, I think.

There was only 1 "long" trail that was open. I started on the Peterson trail, which is quite steep. It then merges with Sanborn trail and then goes all the way to meet the Skyline trail. It's about 2.4 miles to the Skyline trail, may be a little more. I continued for a few minutes on Skyline. Stopped for a snack and then headed back on the same Sanborn and Peterson trails.

Every time I go hiking under the Redwoods, I've noticed a sweet, mildly smoky, intoxicating smell usually where there is a patch on sunlight. I've tried stopping to get a second lung full and never managed to find it again. It's been driving me nuts. This strange, ephemeral smell always reminds me of the weird Picnic at Hanging Rock movie.

Until next time...

Saturday, June 20, 2009

Trouble with Schemas

I had to spend some time this week working on XML schemas. The trouble with schemas is that you can go all out and implement an almost object-oriented inheritance hierarchy. Which is exactly what I did.

I unwittingly set foot into the rarefied area of substitutionGroups and the like. And trying to find information when you don't know what to look for is a huge problem. So to save you the trouble and for my own future reference, here's what I learned. I could be wrong in several places, but it should be a good starting point for you.

This is what I was I had in mind. I needed a generic Object and a simple Collection-like container that could hold 1 or more Objects. And if you are not using XMLSpy...well good luck!

This is what the Object looks like:


<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns="http://www.javaforu.com/schemas/lesson1" xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.javaforu.com/schemas/lesson1" elementFormDefault="qualified" attributeFormDefault="unqualified">

<xs:complexType name="GenericObjectType"></xs:complexType>

<xs:element name="GenericObject" type="GenericObjectType"></xs:element>

</xs:schema>


And this is what the Object Collection looks like:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns="http://www.javaforu.com/schemas/lesson1" xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.javaforu.com/schemas/lesson1" elementFormDefault="qualified" attributeFormDefault="unqualified">


<xs:complexType name="GenericObjectCollectionType">
<xs:sequence>
<xs:element ref="GenericObject" maxOccurs="unbounded"></xs:element>
</xs:sequence>
</xs:complexType>

<xs:element name="GenericObjectCollection" type="GenericObjectCollectionType"></xs:element>

</xs:schema>


That was easy enough. What I need now is a Person object that inherits from Object.


<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns="http://www.javaforu.com/schemas/lesson1" xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.javaforu.com/schemas/lesson1" elementFormDefault="qualified" attributeFormDefault="unqualified">


<xs:complexType name="PersonType">
<xs:complexContent>
<xs:extension base="GenericObjectType">
<xs:sequence>
<xs:element name="firstName" type="xs:string"></xs:element>
<xs:element name="lastName" type="xs:string"></xs:element>
<xs:element name="age" type="xs:positiveInteger"></xs:element>
<xs:element name="gender" type="xs:string"></xs:element>
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>

<xs:element name="Person" type="PersonType" substitutionGroup="GenericObject"></xs:element>

</xs:schema>


Note the use of substitutionGroup="GenericObject" in the Person element. This means that I can create Person tags/elements where ever GenericObject tags are allowed. That's very cool!

Here comes the clincher..If I need a special PersonCollection that only allows Person objects but still inherits from the GenericCollection, this is what I'd have to do:


<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns="http://www.javaforu.com/schemas/lesson1" xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.javaforu.com/schemas/lesson1" elementFormDefault="qualified" attributeFormDefault="unqualified">


<xs:complexType name="PersonCollectionType">
<xs:complexContent>
<xs:restriction base="GenericObjectCollectionType">
<xs:sequence>
<xs:choice maxOccurs="unbounded">
<xs:element ref="Person"></xs:element>
</xs:choice>
</xs:sequence>
</xs:restriction>
</xs:complexContent>
</xs:complexType>

</xs:schema>


Now, pay attention: For some reason, I'm yet to discover why, you cannot just replace the ref to the GenericObject with a Person ref when you have an unbounded occurrence rule. Try it. It has to be wrapped in a choice rule.

And of course the substitutionGroup="GenericObjectCollection" will you use the PersonCollection where ever the GenericCollection is allowed.

<xs:element name="PersonCollection" substitutionGroup="GenericObjectCollection"></xs:element>


This is what a sample looks XML like:

<?xml version="1.0" encoding="UTF-8"?>
<DocRoot xmlns="http://www.javaforu.com/schemas/lesson1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.javaforu.com/schemas/lesson1 Lesson1.xsd">

<GenericObject></GenericObject>

<Person>
<firstName>sdsfxcv</firstName>
<lastName>xsdf</lastName>
<age>12</age>
<gender>m</gender>
</Person>

<GenericObjectCollection>
<GenericObject></GenericObject>

<Person>
<firstName>asd</firstName>
<lastName>fgdfgd</lastName>
<age>77</age>
<gender>f</gender>
</Person>
</GenericObjectCollection>

<PersonCollection>
<Person>
<firstName>abcd</firstName>
<lastName>def</lastName>
<age>20</age>
<gender>m</gender>
</Person>
</PersonCollection>

</DocRoot>


And the full schema:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns="http://www.javaforu.com/schemas/lesson1" xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.javaforu.com/schemas/lesson1" elementFormDefault="qualified" attributeFormDefault="unqualified">

<xs:complexType name="GenericObjectType"/>

<xs:complexType name="GenericObjectCollectionType">
<xs:sequence>
<xs:element ref="GenericObject" maxOccurs="unbounded"></xs:element>
</xs:sequence>
</xs:complexType>

<xs:complexType name="DocRootType">
<xs:sequence>
<xs:element ref="GenericObject" minOccurs="0" maxOccurs="unbounded"></xs:element>
<xs:element ref="GenericObjectCollection" minOccurs="0" maxOccurs="unbounded"></xs:element>
</xs:sequence>
</xs:complexType>

<xs:element name="GenericObject" type="GenericObjectType"></xs:element>
<xs:element name="GenericObjectCollection" type="GenericObjectCollectionType"></xs:element>
<xs:element name="DocRoot" type="DocRootType"></xs:element>

<!---->

<xs:complexType name="PersonType">
<xs:complexContent>
<xs:extension base="GenericObjectType">
<xs:sequence>
<xs:element name="firstName" type="xs:string"></xs:element>
<xs:element name="lastName" type="xs:string"></xs:element>
<xs:element name="age" type="xs:positiveInteger"></xs:element>
<xs:element name="gender" type="xs:string"></xs:element>
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>

<xs:complexType name="PersonCollectionType">
<xs:complexContent>
<xs:restriction base="GenericObjectCollectionType">
<xs:sequence>
<xs:choice maxOccurs="unbounded">
<xs:element ref="Person"></xs:element>
</xs:choice>
</xs:sequence>
</xs:restriction>
</xs:complexContent>
</xs:complexType>

<xs:element name="Person" type="PersonType" substitutionGroup="GenericObject"></xs:element>
<xs:element name="PersonCollection" substitutionGroup="GenericObjectCollection"></xs:element>

</xs:schema>


If you find any mistakes or have any other such interesting bits of information to share, I'd love to hear it.

Sunday, June 14, 2009

Pycon 2009 talk - Drop ACID and think about data

This is worth watching - Drop ACID and think about data. A nice summary of current cluster/cache/distributed db technologies.

Thursday, June 11, 2009

Flame back wood pecker


Flame back wood pecker, originally uploaded by SRJP.

Pic taken by my dad - Dr Jayaprakash, Bangalore

Bush chat male


Bush chat male, originally uploaded by SRJP.

Pic taken by my dad - Dr Jayaprakash, Bangalore

Jungle fowl


Jungle fowl, originally uploaded by SRJP.

Pic taken by my dad - Dr Jayaprakash, Bangalore

Serpent eagle


Serpent eagle, originally uploaded by SRJP.

Pic taken by my dad - Dr Jayaprakash, Bangalore

Lark


Lark, originally uploaded by SRJP.

Pic taken by my dad - Dr Jayaprakash, Bangalore

Blue tailed bee eater


Blue tailed bee eater, originally uploaded by SRJP.

Pic taken by my dad - Dr Jayaprakash, Bangalore

Tuesday, June 09, 2009

A cool 100K open network connections

A nice read - 100K simultaneous connections using Java NIO, actually Netty.

Saturday, June 06, 2009

Beautiful visualization of Huffman encoding

How I wish all algorithms were animated and illustrated this well - Huffman encoding. Yay! I now know how compression works.

Tuesday, June 02, 2009

Java powered Netbooks

This is interesting - Oracle's Ellison considers netbook market foray.

Also interesting to hear that JavaFx will get more support. Strange.. considering the fact that most people thought JavaFx/Desktop Java would die after the Oracle acquisition. More hints here with Larry Ellison and Scott McNealy on stage at the JavaOne 2009 inauguration (at 1:38:11). Not just that but he was also eyeing the Google Android Netbook market. Seems natural enough to mere mortals like us now that the visionaries have laid out a plan of attack on the pseudo-JVM that is Android.

As an aside - Acer to sell Android netbook PCs in Q3.