Presented to Birmingham University in 2010 as part of the Computer Science - Commercial Programming course.

1. Software Development with "
Open Source
Jon Allen (JJ) – jj@opusvl.com
Birmingham University 2010
Software Development with Open Source
Open Source Business Systems
www.opusvl.com

2. About OpusVL
• Open Source development company
• Based in Rugby, UK
• Founded in 2000
• Business systems (ERP, VOIP, CRM, etc)
• Bespoke software development
• Use and contribute to Open Source
– Code
– Sponsorship
Software Development with Open Source
Open Source Business Systems
www.opusvl.com

3. Open Source
• Who uses Open Source software?
Software Development with Open Source
Open Source Business Systems
www.opusvl.com

4. Open Source
• Who uses Open Source software?
• Who uses…
– Google
– Facebook
– BBC iPlayer
– Amazon
Software Development with Open Source
Open Source Business Systems
www.opusvl.com

5. Open Source
• Who uses Open Source software?
• Who uses…
– Google
– Facebook
– BBC iPlayer
– Amazon
• All built on Open Source software
Software Development with Open Source
Open Source Business Systems
www.opusvl.com

6. What is Open Source Software?
• Licensing model
– Free redistribution
– Source code available
– Modifications and derived works allowed
• Distribution allowed under same terms as original licence
– No discrimination against people or fields of usage
• Typical licenses
– BSD, Apache, GPL, Artistic
• Restrictions vary by license (BSD vs. Copyleft)
Software Development with Open Source
Open Source Business Systems
www.opusvl.com

7. Why Open Source?
• Try before you buy
– Use first, get support later
– Open documentation, support forums, etc
• Source code available
– Can make changes and fix bugs
• Freedom to fork
– No vendor lock-in
• Access to developers
– Speak directly to the author
Software Development with Open Source
Open Source Business Systems
www.opusvl.com

8. What do we use?
• Products
– Debian, Ubuntu, Apache, PostgreSQL, CouchDB,
Asterisk, XEN, OpenERP, DAViCal, Memcached, etc.
• Development tools
– Perl
– Catalyst, Moose, DBIx::Class, Template Toolkit,
DateTime, HTML::FormFu, etc.
Software Development with Open Source
Open Source Business Systems
www.opusvl.com

9. Perl
• Multi-paradigm programming language
– Procedural, Functional, Object-Oriented
• Mature, stable, scalable
– Used in mission-critical systems across the globe
– BBC, Cisco, Amazon, Vodafone, LOVEFiLM
– http://www.perl.org
• Perl 5, version 12.2
– Released 7th September 2010
Software Development with Open Source
Open Source Business Systems
www.opusvl.com

10. CPAN
• Comprehensive Perl Archive Network
– Over 21,000 modules - Perl’s “killer app”
• Interfaces, frameworks, applications, dev tools, file
formats, imaging, databases, and lots more
• Code reuse
– Don’t re-invent the wheel
– Building blocks for applications
• http://search.cpan.org
Software Development with Open Source
Open Source Business Systems
www.opusvl.com

11. Quality Assurance
• Perl has a strong QA culture
• Test-driven development
• CPAN Testers
– Automated testing community
– Every CPAN upload tested with multiple platforms
and Perl versions
– 9,000,000 test reports (500,000 per month)
– http://www.cpantesters.org
Software Development with Open Source
Open Source Business Systems
www.opusvl.com

12. Community
• Perl Mongers – local user groups
– Birmingham, London, Milton Keynes, North West
– http://birmingham.pm.org
• Conferences and workshops
– YAPC – Europe, Asia, Russia, North America
– http://conferences.yapceurope.org/lpw2010
• Online
– http://blogs.perl.org
– Forums, IRC, mailing lists
Software Development with Open Source
Open Source Business Systems
www.opusvl.com

13. Jobs
• Contribute to Open Source projects
– Very impressive on your CV
– Great way to gain experience
• Not just programming
– Documentation, testing, bug triage
• User groups
– Perl Mongers, LUGs, UKUUG, Multipack, PyWM
– Networking – get yourself known
Software Development with Open Source
Open Source Business Systems
www.opusvl.com

14. Software Stack
Client customisations • Core framework
– Catalyst
Client OpusVL
application
components
application
components
– Moose
– DBIx::Class
OpusVL framework modules
DBMS
Core framework modules Ingres,
Catalyst, Moose, DBIx::Class, etc PostgreSQL,
CouchDB, etc
Base software stack
Linux, Apache, Perl
Software Development with Open Source
Open Source Business Systems
www.opusvl.com

15. DBIx::Class
• ORM – Object Relational Mapper
– Database abstraction layer
• Creates objects, classes, and methods
• Writes SQL – improves maintainability
• Easily add new class methods
– Business logic
– Encapsulation
• Use methods, not database queries
Software Development with Open Source
Open Source Business Systems
www.opusvl.com

16. DBIx::Class Schema
• Describes tables and relationships
– Loaded from DB – DBIx::Class::Schema::Loader
CREATE TABLE authors (
id integer primary key,
name text
);
CREATE TABLE books (
id integer primary key,
author_id integer,
title text,
foreign key(author_id) references authors(id)
);
dbicdump Authors 'dbi:SQLite:test.db'
Software Development with Open Source
Open Source Business Systems
www.opusvl.com

17. Using generated classes
• Gives us an Authors class
– Relationships converted to class methods
use Authors;
my $db = Authors->connect("dbi:SQLite:test.db");
my $author = $db->resultset("Author")
->find(name => "Stephen King");
foreach my $book ($author->books) {
say $book->title;
say $book->author->name;
}
Software Development with Open Source
Open Source Business Systems
www.opusvl.com

18. Extending classes
• With a “rate” method added to the Book class
# in Authors/Result/Author.pm
use List::Utils qw/sum/;
sub is_liked {
my $self = shift;
my $total = sum(
map {$_->rating} $self->books->all
);
return ($total / $self->books->count) > 3;
}
Software Development with Open Source
Open Source Business Systems
www.opusvl.com

19. Moose
• Object Oriented programming framework
• Extension of Perl’s native OO
• Improves syntax and facilities
– Method modifiers, introspection, roles, type checking
• Large developer community
• http://moose.perl.org
Software Development with Open Source
Open Source Business Systems
www.opusvl.com

20. Moose example
use MooseX::Declare
class Report extends ‘Document’
with ‘Confidentiality’ {
has ‘total’ => (isa => ‘Num’, default => ‘1000’);
has ‘notes’ => (isa => ‘Str’);
method fake_data {...}
}
role Confidentiality {
before print {
# hide any incriminating data!
};
}
Software Development with Open Source
Open Source Business Systems
www.opusvl.com

21. Catalyst
• Web development framework
• Application server
• Scalable, high performance
– Powers some of the world’s biggest websites
• Structured, maintainable
– URLs dispatched to class methods
• DRY – Don’t Repeat Yourself
– Modular, self-contained components
Software Development with Open Source
Open Source Business Systems
www.opusvl.com

22. What does Catalyst provide?
• Session handling
• Authentication / access control
• Page caching
• Built-in development server
• URL generation
– What’s the URL to reach this method?
• Library of pre-built components
Software Development with Open Source
Open Source Business Systems
www.opusvl.com

23. Catalyst block diagram
View
Stash
User Controller
Model
Business Logic DB
Software Development with Open Source
Open Source Business Systems
www.opusvl.com

24. Model
• Business logic
• Interface to a class
– Data storage (DBIx::Class, LDAP, S3, data files)
– API (REST, SOAP, XMLRPC)
– External system (OpenERP, Asterisk, hardware)
– Any other piece of Perl code
• External to Catalyst
– Used and maintained separately
Software Development with Open Source
Open Source Business Systems
www.opusvl.com

25. View
• Presentation logic
• Renders output as…
– HTML, XML, JSON, PDF, Excel, JPEG, PNG, etc.
– Template::Toolkit
• Messaging
– Email, SMS
• Processing
– Generating thumbnail images
Software Development with Open Source
Open Source Business Systems
www.opusvl.com

26. Controller
• Application logic
– Links Models to Views
• Passes input to the model
• Puts data from the model onto the stash
• Runs the application
– Control flow
– Logging / error handling
– Status codes
Software Development with Open Source
Open Source Business Systems
www.opusvl.com

27. Conclusion
• Open Source gives us the tools to deliver
• The Community makes it possible
• Birmingham Perl Mongers
– http://birmingham.pm.org
• Birmingham Linux User Group
– http://birmingham.lug.org.uk
Software Development with Open Source
Open Source Business Systems
www.opusvl.com

28. Essay question
• Open Source software is often perceived as being non-
commercial as free redistribution is permitted. However,
many companies have managed to turn both the
development and usage of Open Source software into a
profitable business.
– Research the different business models that companies use
to derive commercial benefit from Open Source software.
– Investigate the challenges that companies face in managing
external development and user communities.
Software Development with Open Source
Open Source Business Systems
www.opusvl.com