Just a Theory

By David E. Wheeler

bricolage.cc Has a New Server

The Bricolage project has a new server! Thanks to a generous donation from NetStumbler.com, we have a shiny new hosted FreeBSD server. I’ve started building it, and have migrated the Bricolage Web site over today. By tomorrow, DNS records should be updated, and it’ll be rarin’ to go!

While I was at it, I rolled out the new Bricolage API documentation browser. There are now browser available for all of the major stable releases of Bricolage, listed on the old documentation page. The API browser for the current stable release will always be available here. Meanwhile, the documentation will also be generated from the Subversion trunk every morning; you can find those docs here.

We’ll also be able to keep better track of the kind of traffic the site gets thanks to the new stats site, which will also be updated daily.

Enjoy!

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Perl.org Subversion Authentication Woes

It looks like the Perl.org authentication system that handles authentication for svn.bricolage.cc doesn’t properly cache an authentication token. Robert discovered this when a very large merge I was working on from the rev_1_8 branch of Bricolage to trunk was hanging and then timing out on me. The problem was that it was disconnecting from the MySQL server. Odd. At any rate, Robert switched over to an auth system that doesn’t use MySQL so that I could do the merge and then the commit. This morning, he restored the original auth system. I shouldn’t often have to do such a big merge or commit in Bricolage, so hopefully it won’t come up again, but it sure was annoying there for a while.

So for my fellow Bricolage developers who thought that the auth system was down: Sorry, it’s back now. And the trunk is fully updated with all of the changes to rev_1_8, which means that new development in the trunk can begin again in earnest.

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Blosxom Rewrite Rules

I finally got my mod_rewrite rules working for Blosxom, so now it finally looks like I have a real site! The problem was that %{REQUEST_FILE} wasn’t actually the full file name on the file system, but the request URI! I have no idea why, but once I figured out this problem I was able get ‘round it by using %{DOCUMENT_ROOT}%{REQUEST_URI}. So now my configuration looks like this:

<VirtualHost *>
  DocumentRoot /usr/local/www/doc_roots/justatheory
  ServerAdmin david@justatheory.com
  ServerName justatheory.com
  ServerAlias www.justatheory.com
  CustomLog /usr/local/www/logs/access_log.justatheory combined
  <Directory /usr/local/www/doc_roots/justatheory>
    AddHandler cgi-script .cgi
    Options +ExecCGI
  </Directory>
  RewriteEngine on
  RewriteCond %{DOCUMENT_ROOT}%{REQUEST_URI} !-f
  RewriteCond %{DOCUMENT_ROOT}%{REQUEST_URI} !-d
  RewriteRule ^/(.*)$ /blosxom.cgi/$1 [L,QSA]
</VirtualHost>

And all is well. Now, if only I could get the meta plugin working properly…

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How to Extend Bricolage 2.0

Going through the latest version of the Bricolage 2.0 technical specification, I can see at least six ways that developers will easily be able to extend Bricolage:

Write a new task by subclassing Bricolage::Biz::Task
A task can be designed to do just about anything to a single Bricolage object. Hell, you’d be able to look up other objects, too, so anything’s possible. Tasks are run by scheduled jobs, event-triggered actions, or by distribution jobs.
Create a new data type by subclassing Bricolage::Biz::Value and Bricolage::Biz::Type::Value
We’ll support quite a few different value types to start with, but we couldn’t anticipate everything, so this’ll be your chance!
Create a new UI widget by subclassing Bricolage::Widget and Bricolage::Biz::Type::Widget
Maybe your new value requires its own special widget. Or maybe you don’t like the way the existing widgets handle other types of values. So write your own!
Write a new distribution mover by subclassing Bricolage::Biz::Dist::Mover
We’ll start out with file system copy, SFTP, SFTP, and WebDAV distribution movers just as we have in Bricolage 1.8, but there’s always room for more!
Write a new authentication plugin by subclassing Bricolage::Util::Auth
The built-in and LDAP-based authentication systems aren’t doing it for you? You want to authenticate against a different database? Make it so!
Write a new storage back-end by subclassing Bricolage::Store
We’ll have a PostgreSQL back-end from the start, and perhaps SQLite and/or MySQL. But here’s your chance to get Bricolage running on FileMaker Pro just as you’ve always secretly desired!

So have fun with it! When it gets here. Want to help get get here? Subscribe to Bricolage-Devel and chip in!

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Bricolage Tasks, Jobs, Actions, and Alerts

I’ve been working on the design for what are called distribution jobs and alerts in Bricolage 1.x. There were some good ideas there. Distribution jobs enable users to set up a list of tasks to execute against the files being distributed, such as validating them against a DTD or distributing them via email. It also allowed developers to create fairly simple plugin modules that could be added as new jobs. Alerts are great ways of letting users know that some even has happened, and their rules-based evaluation of event attributes is a powerful way of configuring alerts to be sent only for certain events logged for certain objects.

The problem is that they’re specific solutions to general problems. Distribution job s are an example of scheduling arbitrary tasks to be executed, while alerts are an example of triggering the execution of arbitrary tasks upon the logging of an event. So what I’ve been working on is trying to generalize these ideas into a simpler yet more powerful and flexible architecture. What I’ve come with is this:

Tasks

Very simply, a task is an object of a class designed to perform a simple, um task. Examples include publishing a document, expiring a document, sending an alert, or validating a file against a DTD. An abstract base class, Bricolage::Biz::Task, will establish the the interface for tasks, although its subclasses may add their own attributes (such as the subject and message of an alert). Each will implement an execute() method that will simply carry out the task on the object passed to it. Some task classes may operate on only one type of object (such as Task::Publish), while others may operate on many or even all Bricolage business classes (such as Task::SendAlert). There is no connection between task classes and events or jobs, except that the object that called the task object’s execute() method will be passed to execute() as a second argument.

Actions

An action is an event-triggered series of tasks. New action types can be created that have rules set to be evaluated against the event, just as is currently the case for alert types in Bricolage 1.x. The difference is that rather than being limited to sending alerts, actions types will be associated with one or more task objects, and each of those tasks will be executed in sequence when an action of that type is triggered. This will enable users to, for example, configure an action to republish an index document whenever a story document is published.

Jobs

A job is a scheduled series of tasks. Users will be able to create new jobs for any single object in Bricolage, associate any number of task objects, and then schedule the job to be run at some specific date and time in the future. This approach will enable users to, for example, schedule a job to send an alert about a given document one year in the future, as a reminder to update the document.

Destinations

Destinations will be similar to what’s currently in Bricolage 1.x. However, rather than having “job” classes specific to distribution, they’ll be able to specify a list of any tasks that are designed to be executed against an output file. This keeps the interface for tasks identical across all three uses.

Alerts

Alerts are no longer closely tied to events, since they can sent as part of a scheduled job or as part of a distribution to a destination in addition to when an event is logged. Rather, they will only be created by Bricolage::Biz::Task::SendAlert. So a Bricolage business object can have any number of associated alerts, just as it can have any number of associated events.

Upshot

The upshot of this redesign, which took me several days of thinking to tease out to be general enough to satisfy me, is that more users will have more of what they need from Bricolage, and developers can more easily add new functionality that’s immediately available to event actions, scheduled jobs, and distribution destinations.

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My Adventures with Mac OS X

I recently decided to make the leap from Yellow Dog Linux to Mac OS X on my Titanium PowerBook. Getting everything to work the way I wanted proved to be a challenge, but well worth it. This document outlines all that I learned, so that neither you nor I will have to experience such pain again. The overall goal was to get Bricolage up and running, figuring that if it worked, then just about any mod_perl based solution would run. I’m happy to say that I was ultimately successful. You can be, too.

In the descriptions below, I provide links to download the software you’ll need, as well as the shell commands I used to compile and install each package. In all cases (except for the installation of the Developer Tools), I saved each package’s sources to /usr/local/src and gunzipped and untarred them there. I also carried out each step as root, by running sudo -s. If you’re not comfortable using a Unix shell, you might want to read up on it, first. All of my examples also assume a sh-compatible shell, such as bash or zsh. Fortunately, zsh comes with OS X, so you can just enable it for yourself in NetInfo Manager by setting users -> <username> -> shell to “/bin/zsh”, where <username> is your user name.

Developer Tools

All of the software that I describe installing below must be compiled. To compile software on Mac OS X, you need to install the Mac OS X Developer Tools. These provide the cc compiler and many required libraries. Conveniently, these come on a CD-ROM with the Mac OS X Version 10.1 upgrade kit. I just popped in the CD and installed them like you’d install any other OS X software. I needed administrative access to OS X to install the Developer Tools (or, indeed, to install any of the other software I describe below), but otherwise it posed no problems.

The best time to install the Developer Tools is immediately after upgrading to OS X version 10.1. Then run the Software Update applet in the System preferences to get your system completely up-to-date. By the time I was done, I had the system updated to version 10.1.3.

Emacs

The first step I took in the process of moving to OS X was to get working the tools I needed most. Essentially, what this meant was GNU Emacs. Now I happen to be a fan of the X version of Emacs – not XEmacs, but GNU Emacs with X support built in. I wasn’t relishing the idea of having to install X on OS X (although there are XFree86 ports that do this), so I was really pleased to discover the Mac-Emacs project. All I had to do was patch the GNU Emacs 21.1 sources and compile them, and I was ready to go! GNU Emacs works beautifully with the OS X Aqua interface.

There were a few configuration issues for me to work out, however. I have become addicted to the green background that an old RedHat .XConfig file had set, and I wanted this feature in OS X, too. Plus, the default font was really ugly (well, too big, really – anyone know how to make it smaller in Emacs?) and the Mac command key was working as the Emacs META key, rather than the option key. So I poked around the net until I found the settings I needed and put them into my .emacs file:

(custom-set-faces
'(default ((t (:stipple nil
  :background "DarkSlateGrey"
  :foreground "Wheat"
  :inverse-video nil
  :box nil
  :strike-through nil
  :overline nil
  :underline nil
  :slant normal
  :weight normal
  :height 116
  :width normal
  :family "apple-andale mono"))))
'(cursor ((t (:background "Wheat"))))
; Use option for the meta key.
(setq mac-command-key-is-meta nil)

Installing Emacs is not required for installing any of the other packages described below – it just happens to be my favorite text editor and IDE. So I don’t provide the instructions here; the Mac-Emacs project does a plenty good job. If you’re not comfortable with Unix editors, you can use whatever editor you like. BBEdit is a good choice.

GDBM

Mac OS X doesn’t come with a DBM! But since mod_ssl needs it, we have to install it. Fortunately, I found this PDF detailing someone else’s adventures with mod_ssl on OS X, and it provided decent instructions for installing GDBM. First, I created a new user for GDBM. In NetInfoManager, I created a duplicate of the “unknown” user and named it “bin”. Then, I downloaded GDBM from the FSF, and installed it like this:

cd /usr/local/src/gdbm-1.8.0
cp /usr/libexec/config* .
./configure
make
make install
ln -s /usr/local/lib/libgdbm.a /usr/local/lib/libdbm.a

That did the trick. Nothing else was involved, fortunately.

Expat

Who doesn’t do something with XML these days? If your answer is, “not me!”, then you’ll need to install the Expat library in order to work with XML::Parser in Perl. Fortunately it’s relatively easy to install, although support for the -static flag appears to be broken in cc on OS X, so it needs to be stripped out. I downloaded it from its project bpage, and then did this:

cd /usr/local/src/expat-1.95.2
./configure
perl -i.bak -p -e \
  's/LDFLAGS\s*=\s*-static/LDFLAGS=/' \
  examples/Makefile
perl -i.bak -p -e \
  's/LDFLAGS\s*=\s*-static/LDFLAGS=/' \
  xmlwf/Makefile
make
make install

Perl

Although Mac OS X ships with Perl (Yay!), it’s the older 5.6.0 version. There have been many bug fixes included in 5.6.1, so I wanted to make sure I got the latest stable version before I built anything else around it (mod_perl, modules, etc.).

Being a Unix program, Perl doesn’t expect to run into the problems associated with a case-insensitive file system like that Mac OS X’s HFS Plus. So there are a couple of tweaks to the install process that make it slightly more complicated than you would typically expect. Fortunately, many have preceded us in doing this, and the work-arounds are well-known. Basically, it comes down to this:

cd /usr/local/src/perl-5.6.1/
export LC_ALL=C
export LANG=en_US
perl -i.bak -p -e 's|Local/Library|Library|g' hints/darwin.sh
sh Configure -des -Dfirstmakefile=GNUmakefile -Dldflags="-flat_namespace"
make
make test
make install

There were a few errors during make test, but none of them seems to be significant. Hopefully, in the next version of Perl, the build will work just as it does on other platforms.

Downloads

Before installing Open SSL, mod_ssl, mod_perl, and Apache, I needed to get all the right pieces in place. The mod_ssl and mod_perl configure processes patch the Apache sources, so the Apache sources have to be downloaded and gunzipped and untarred into an adjacent directory. Furthermore, the mod_ssl version number corresponds to the Apache version number, so you have to be sure that they match up. Normally, I would just download the latest versions of all of these pieces and run with it.

However, Bricolage requires the libapreq library and its supporting Perl modules to run, and these libraries have not yet been successfully ported to Mac OS X. But worry not; fearless mod_perl hackers are working on the problem even as we speak, and there is an interim solution to get everything working.

As of this writing, the latest version of Apache is 1.3.24. But because I needed libapreq, I had to use an experimental version of Apache modified to statically compile in libapreq. Currently, only version 1.3.23 has been patched for libapreq, so that’s what I had to use. I discovered this experimental path thanks to a discussion on the Mac OS X Perl mail list.

So essentially what I did was download the experimental apache.tar.gz and the experimental lightweight apreq.tar.gz packages and gunzip and untar them into /usr/local/src. Then I was ready to move on to Open SSL, mod_ssl, and mod_perl.

Open SSL

Compiling Open SSL was pretty painless. One of the tests fails, but it all seems to work out, anyway. I download the sources from the Open SSL site, and did this:

cd /usr/local/src/openssl-0.9.6c
./config
make
make test

mod_ssl

The mod_ssl Apache module poses no problems whatsoever. I simply downloaded mod_ssl-2.8.7-1.3.23 from the mod_ssl site (note that the “1.3.23” at the end matches the version of Apache I downloaded) and gunzipped and untarred it into /usr/local/src/. Then I simply excuted:

./configure --with-apache=/usr/local/src/apache_1.3.23

mod_perl

Configuring and installing mod_ssl was, fortunately, a relatively straight-forward process. Getting Apache compiled with mod_perl and mod_ssl, however, was quite tricky, as you’ll see below. A number of braver folks than I have preceded me in installing mod_perl, so I was able to rely on their hard-earned knowledge to get the job done. For example, Randal Schwartz posted instructions to the mod_perl mail list, and his instructions worked well for me. So I downloaded the sources from the mod_perl site, and did this:

cd /usr/local/src/mod_perl-1.26
perl Makefile.PL \
  APACHE_SRC=/usr/local/src/apache_1.3.23/src \
  NO_HTTPD=1 \
  USE_APACI=1 \
  PREP_HTTPD=1 \
  EVERYTHING=1
make
make install

Apache

Getting Apache compiled just right was the most time-consuming part of this process for me. Although many had gone before me in this task, everybody seems to do it differently. I had become accustomed to just allowing Apache to use most of its defaults when I compiled under Linux, but now I was getting all kinds of errors while following different instructions from different authorities from around the web. Sometimes Apache wouldn’t compile at all, and I’d get strange errors. Other times it would compile, pass all of its tests, and install, only to offer up errors such as

dyld: /usr/local/apache/bin/httpd Undefined symbols: _log_config_module

when I tried to start it. It turns out that the problem there was that I had a number of modules compiled as DSOs – that is, libraries that can be loaded into Apache dynamically – but wasn’t loading them properly in my httpd.conf. This was mainly because I’ve grown accustomed to Apache having all the libraries I needed compiled in statically, so I simply didn’t have to worry about them.

But I finally hit on the right incantation to get Apache to compile with everything I need added statically, but still with support for DSOs by compiling in mod_so. I present it here for your viewing pleasure:

SSL_BASE=/usr/local/src/openssl-0.9.6c/ \
    ./configure \
    --with-layout=Apache \
    --enable-module=ssl \
    --enable-module=rewrite \
    --enable-module=so \
    --activate-module=src/modules/perl/libperl.a \
    --disable-shared=perl \
    --without-execstrip
  make
  make certificate TYPE=custom 
  make install

This series of commands successfully compiled Apache with mod_perl and mod_ssl support statically compiled in, along with most of the other default modules that come with Apache. In short, everything is there that you need to run a major application with security such as Bricolage.

Note that make certificate will lead you through the process of creating an SSL certificate. I like to use the “custom” type so that it reflects the name of my organization. But you can use whatever approach you’re most comfortable with. Consult the mod_ssl INSTALL file for more information.

libapreq

Once Apache is installed with mod_perl and mod_ssl, the rest is gravy! The experimental libapreq library I downloaded installed without a hitch:

cd /usr/local/src/httpd-apreq
perl Makefile.PL
make
make install

PostgreSQL

PostgreSQL is a sophisticated open-source Object-Relational DBMS. I use it a lot in my application development, and it, too, is required by Bricolage. I was a bit concerned about how well it would compile and work on Mac OS X, but I needn’t have worried. First of all, Apple has provided some pretty decent instructions. Although they mainly document how to install MySQL, a competing open-source RDBMS, many of the same concepts apply to PostgreSQL.

The first thing I had to do was to create the “postgres” user. This is the system user that PostgreSQL typically runs as. I followed Apple’s instructions, using NetInfo Manager to duplicate the default “www” group and “www” user and give the copies the name “postgres” and a new gid and uid, respectively.

Next I downloaded the PostgreSQL version 7.2.1 sources. Version 7.2 is the first to specifically support Mac OS X, so going about the install was as simple as it is on any Unix system:

./configure --enable-multibyte=UNICODE
make
make install

That was it! PostgreSQL was now installed. Next I had to initialize the PostgreSQL database directory. Again, this works much the same as it does on any Unix system:

sudo -u postgres /usr/local/pgsql/bin/initdb \
  -D /usr/local/pgsql/data

The final step was to start PostgreSQL and try to connect to it:

sudo -u postgres /usr/local/pgsql/bin/pg_ctl start \
  -D /usr/local/pgsql/data /usr/local/pgsql/bin/psql -U postgres template1

If you follow the above steps and find yourself at a psql prompt, you’re in business! Because I tend to use PostgreSQL over TCP, I also enabled TCP connectivity by enabling the “tcpip_socket” option in the postgresql.conf file in the data directory created by initdb:

tcpip_socket = true

If you’re like me, you like to have servers such as PostgreSQL start when your computer starts. I enabled this by creating a Mac OS X PostgreSQL startup bundle. It may or may not be included in a future version of PostgreSQL, but in the meantime, you can download it from here. Simply download it, gunzip and untar it into /Library/StartupItems, restart OS X, and you’ll see it start up during the normal Mac OS X startup sequence. I built this startup bundle by borrowing from the existing FreeBSD PostgreSQL startup script, the Apache startup script that ships with OS X, and by reading the Creating SystemStarter Startup Item Bundles HOWTO.

XML::Parser

At this point, I had most

of the major pieces in place, and it was time for me to install the Perl modules I needed. First up was XML::Parser. For some reason, XML::Parser can’t find the expat libraries, even though the location in which I installed them is pretty common. I got around this by installing XML::Parser like this:

perl Makefile.PL EXPATLIBPATH=/usr/local/lib \
  EXPATINCPATH=/usr/local/include
make
make test
make install

Text::Iconv

In Bricolage, Text::Iconv does all the work of converting text between character sets. This is because all of the data is stored in the database in Unicode, but we wanted to allow users to use the character set with which they’re accustomed in the UI. So I needed to install Text::Iconv. Naturally, Mac OS X doesn’t come with libiconv – a library on which Text::Iconv depends – so I had to install it. Fortunately, it was a simple process to download it and do a normal build:

cd /usr/local/src/libiconv-1.7
./configure
make
make install

Now, Text::Iconv itself was a little more problematic. You have to tell it to look for libiconv by adding the -liconv option to the LIBS key in Makefile.PL. I’ve simplified doing this with the usual Perl magic:

perl -i.bak -p -e \
  "s/'LIBS'\s*=>\s*\[''\]/'LIBS' => \['-liconv'\]/" \
  Makefile.PL
perl Makefile.PL
make
make test
make install

DBD::Pg

Although the DBI installed via the CPAN module without problem, DBD::Pg wanted to play a little less nice. Of course I specified the proper environment variables to install it (anyone know why DBD::Pg’s Makefile.PL script can’t try to figure those out on its own?), but still I got this error during make:

/usr/bin/ld: table of contents for archive:
/usr/local/pgsql/lib/libpq.a is out of date;
rerun  ranlib(1) (can't load from it)

But this was one of those unusual situations in which the error message was helpful. So I took the error message’s advice, and successfully compiled and installed DBD::Pg like this:

ranlib /usr/local/pgsql/lib/libpq.a
export POSTGRES_INCLUDE=/usr/local/pgsql/include
export POSTGRES_LIB=/usr/local/pgsql/lib
perl Makefile.PL
make
make test
make install

LWP

The last piece I needed to worry about customizing when I installed it was LWP. Before installing, back up /usr/bin/head. The reason for this is that LWP will install /usr/bin/HEAD, and because HFS Plus is a case-insensitive file system, it’ll overwrite /usr/bin/head! This is a pretty significant issue, since many configure scripts use /usr/bin/head. So after installing LWP, move /usr/bin/HEAD, GET, & POST to /usr/local/bin. Also move /usr/bin/lwp* to /usr/local/bin. Then move your backed-up copy of head back to /usr/bin.

Naturally, I didn’t realize that this was necessary until it was too late. I installed LWP with the CPAN module, and it wiped out /usr/bin/head. Fortunately, all was not lost (though it took me a while to figure out why my Apache compiles were failing!): I was able to restore head by copying it from the Mac OS X installer CD. I Just popped it in an executed the command:

cp "/Volumes/Mac OS X Install CD/usr/bin/head" /usr/bin

And then everything was happy again.

Bricolage

And finally, the pièce de résistance: Bricolage! All of the other required Perl modules installed fine from Bundle::Bricolage:

perl -MCPAN -e 'install Bundle::Bricolage'

Then I simply followed the directions in Bricolage’s INSTALL file, and started ‘er up! I would document those steps here, but the install process is currently in flux and likely to change soon. The INSTALL file should always be current, however – check it out!

To Be Continued

No doubt my adventures with Unix tools on Mac OS X are far from over. I’ve reported to various authors on the issues I’ve described above, and most will soon be releasing new versions to address those issues. As they do, I’ll endeavor to keep this page up-to-date. In the meantime, I am thoroughly enjoying working with the first really solid OS that Apple has released in years, and thrilled that I can finally have the best of both worlds: a good, reliable, and elegant UI, and all the Unix power tools I can stand! I hope you do, too.

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Software Development Methodology

I feel that it’s important to have a comprehensive approach to software development. It’s not enough to be good at coding, or testing, or writing documentation. It’s far better to excel at managing every step of the development process in order to ensure the quality and consistency of the end-to-end work as well as of the final product. I aim to do just that in my work. Here I briefly outline my methodology for achieving that aim.

First, good software development starts with good planning and research. I strive to attain a thorough understanding of what I’m developing by listening to the people to whom it matters most: the users. By gaining insight into how people in the target market think about the problem space, and by strategizing about how technology can address that space, a picture of the product takes shape. This research coalesces into a set of pragmatic requirements and goals that balance the demands of a realistic development schedule with the needs and desires of the target market.

Once the requirements have been identified, it’s time for prototyping. Task flow diagrams of user interactions model the entire system. Evaluations from the target market refine these schematics, shaping the look and feel of the final product. I cannot emphasize enough the importance of seeking market feedback to build solid and meaningful metaphors into the design. These concepts drive the user experience and make or break the success of the final product. The outcome of this feedback loop will be a UI, terminology, and object design grounded on intuitive concepts, scalable technologies, and a reliable architecture.

Next, a talented development team must be assembled and backed by a dependable, project management-oriented implementation infrastructure. Team-building is crucial for the success of any product, and in software development, a diverse set of engineers and specialists with complementary talents must come together and work as an efficient whole. As a result, I consider it extremely important to create a working culture of which team members want to be a part. Such an environment doesn’t foster a sense of entitlement, but rather of conviviality and excitement. If team members believe in what they’re doing, and they enjoy doing it, then they’re likely to do it well.

And what they’ll do is actually create the software. Each element of the product design must be broken down into its basic parts, fit into a generalizable design, and built back up into meaningful objects. I further require detailed documentation of every interface and implementation, as well as thorough unit testing. In fact, the tests are often written before the interfaces are written, ensuring that they will work as expected throughout the remainder of the development process. All aspects of the application must be implemented according to a scalable, maintainable methodology that emphasizes consistency, quality, and efficiency.

The emphasis on quality naturally continues into the quality assurance phase of the development process. The feature set is locked so that development engineers can work closely with QA engineers to test edge conditions, identify bugs, fix them, and ensure that they remain fixed. I prefer to have QA engineers punish nightly builds with suites of tests while development engineers fix the problems identified by previous days’ tests. QA is considered complete when the product passes all the tests we can dream up.

And finally, once all of the QA issues have been addressed, the final product is delivered. Naturally, the process doesn’t stop there, but starts over – in fact, it likely has already started over. New features must be schematically tested with likely users, and new interfaces designed to implement them. The idea is to end up with a solid product that can grow with the needs of the target market.

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About Just a Theory

David E. “Theory” Wheeler

Just a Theory is an periodically irregular technology and culture blog by David E. Wheeler. If you’d like to get in touch, catch me on Twitter or send email to david at this domain.

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