f3yourmind

If you hate reading lengthy blog posts and dig the mind map view of the world, then add Steve van der Merwe’s blog to your feed gadget.  What I really like is his short quick observations and great views about software development.  But for me, it’s even better that I get to speak to him regularly, in person.  If you’re in the Cape Town area, make a point of finding him and chatting to him.  He makes ubuntu real.

Trust has popped up in so many of my conversations recently.  It came up at home, at a new school that Lia will be starting next term, in the DDD course that I gave earlier in the month, in Peter Hundermark’s scrum master certification course.  And I got a one line email that said this.

The entire world lives on trust. Every aspect in life moves with trust.

The more I think about situations in life that will prove this statement false, the more it seems to hold true.  Even in design it holds true.  Your most fundamental architectural decisions are based on trust and the implementations of that architecture work because of trust.

It’s true for code too.  If you don’t trust the code on which you build or depend, then you might as well write everything yourself, and give up your place on your team.

I was thinking about the AOP with DDD tutorial that I will be giving at OOPSLA this year, and this trust thing came up.  Here again, aspects and the classes into which they get woven, need a trust relationship.  It may seem like a stretch to make that statement, but I think it holds true again.

So, how do you gain trust?  I am not sure, but I think you have give up something first.  Maybe you need to show your vulnerability first, then it becomes easier to let someone into your space.  Then, perhaps, they will let you in to their space too.  When ego walls are erected, then trust finds it hard to grow.  By ego, I don’t mean arrogance, I mean awareness of your self that you hide from others for fear.  Perhaps, it is only when you show your true interface, that the other will worry less about hidden agendas.

In code, trust lies in interfaces and types, not in implementations.  It’s really about trusting the implementation that makes types worthy.  When you trust the type and send it a message and it behaves as expected, then you trust it.  If you request something of an abstract type and the message was received by an instance of a subclass, then you expect the subclass to behave like the abstract type.  You don’t hope that it does behave consistently, you trust that it does!

Trust is tied in with ubuntu too.  You can’t be part of a community nor allow yourself to be defined and shaped by the people around you, if you can’t trust them.  I think ubuntu coding needs trust as one of it’s values.  It’s already a value in XP, and Scrum, and families.  It needs to be in teams, and organisations, and communities and nations too.

Recently I wrote about the fruitless plight of a schizophrenic service.  Now, I think that some of that schizophrenia exists in the ESB too (or is it rubbing off onto the ESB?).  I’ve always felt that the ESB was just another pattern that showed how to isolate things and deal with routing and transformations.  The most common implementation was a messaging gadget with some pluggable framework of sorts for the transformations, and some configurable framework for routing.

With such isolation of parts, it was convenient to not worry about what happened elsewhere when something was thrown to this gadget for processing.  And we started wondering about scalability things and decided that asynchronous was the way to go … disconnected, stateless, etc, all good, well-intentioned things and useful things.

Then the pattern became a product.  And on top of this product we had more products like business process orchestrators or workflow managers.  And below this product we had applications and databases and ftp locations and all sorts of things that catered for every imaginable protocol.  And around all of this we had some enterprise-ish sort of management thing to keep on eye on everything that was happening inside this very busy product.

Then, services moved from applications to the ESB product.  After all, it’s a service and that’s an enterprise service bus, right?  And when the services where moved over to their new home, all the dependencies had to come along too.  And then we started arguing about getting granularity right in the ESB.  I used to just think that the ESB had a proxy of sorts to the service that still was at the application.  Maybe I got it all wrong.

Now this ESB is starting to feel like an Application Server with a messaging gadget, workflow gadget, transformers, routers, protocol handlers.  And some ESB’s have a web server too, since they have browser based management consoles.

Some people also like the idea of a rules engine for their complex domain rules and embedded those in their applications.  Hold on, those content based routers in the ESB also used a rules engine.  Ok, let’s move our rules over to the ESB too.  Cool, my ESB is also a rules engine.

Now, I see people writing the most hellish XML that is meant to do everything from configure routing, define transformations, execute code, persist messages, fire off sets of rules and more.  It reminds me so much of those weird and wonderful stored procedures and cascading triggers that we wrote.  The other day I got a laugh out of a friend when I told him that ESB’s are now DB servers and everyone writes sprocs in XML.

And we tried to do everything in the database server – rules, custom types, defaults, constraints, sprocs, triggers, batch jobs … even jump into a shell and execute something else.  It did not work out very well then.

If I was an ESB, I’d be very confused.  I started life as a pattern with a reasonable implementation using messaging and transformation and routing.  Now all of this.  In fact, I’d be more stressed than confused.

Then again, maybe the ESB is not confused, and maybe the people that use the ESB that are confused.  In fact, if I was one of those people, I’d be stressed too.

I finally got out of neutral and pulled together the first public offering our Domain Driven Design courses in Cape Town, South Africa.  Normally we give these courses on-site with people on the same development team but I thought it may be fun and inspiring to open it up to everyone for a change.  Now I’m all excited again and really looking forward to a diverse mixture of people. Hopefully, I will see some old faces and lots of new people.

The one thing I can tell you is that the course is a very immersive experience.  I really hate lecturing but I enjoy probing conversations and that’s how I give the course. I don’t have answers to the practical work and concerns are addressed as we go along.  As a result, the day takes unexpected turns and routes.  But in the end I get you to the right destination.  Come along; you will leave exhausted, but inspired!

Take the Fast Track to Domain Driven Design

about the course /  course contents / should you attend? / register for the course

factor10 has expanded its services in South Africa to include our advanced and
expert level courses aimed for the software professional.  On September 8-9, 2009,
we will be offering a fast track to DDD for Architects at the BMW Pavilion in
Cape Town.

Who should attend?

This course is for software professionals that want to take the right steps towards
advanced and expert levels in their careers.  Register for this course if you want to …

• learn more than just another syntax and set of tools
• write software for large, long living systems
• increase the quality and maintainability of your design
• design high quality models and use code to represent those models effectively
• develop applications with a good APIs
• add a design edge to your skill set

Why should you learn DDD?

More and more developers and architects realise that learning every detail of a new
API just isn’t the way to deliver the best business value. It’s such a tough balancing
act; focus on the solving the business problem and focus on building working software
with your frameworks.

One way of taking a big leap in the right direction is to learn and apply domain driven
design. It is definitely not abstract and fluffy; it deals a lot with the code also. DDD
leads us to focus on understanding and to communicate that understanding very well;
in language, in design and in code. You will shift your focus away from designing for a
technology, and you will learn to design for the business domain; to the core of the
problems and solutions. Those are the most interesting parts and what your users
and customers really care about.

about the course /  course contents / should you attend? / register for the course

Many big vendors have invested a lot on blue print or reference architectures.  I came across another in recent months.  I witnessed a vendor team moving from client to client implementing this reference architecture as part of their SOA solution.

What were they actually doing? They were mapping the client’s domain to the reference architecture domain and thereby identified reference architecture services that supported the client’s needs.  This most probably works for some people.   But I feel uncomfortable with it because…

• It means translating from one domain to another and back again.  It’s like having one massive bounded context around the reference architecture with a gigantic set of adaptors and transformers.
• There is a very real possibility of semantic impedance on the boundary of the two domains.
• There is likely to be two domain vocabularies or one large polluted vocabulary with synonyms, etc.

There are other reasons but these few are just old problems and habits coming back again.  Things that we accepted as dangerous and limits success in creating good software.

So, are reference architectures bad? Yes and no.  Maybe you should consider adopting its domain vocabulary as a first step.  A reference architecture with a rich metamodel is more likely to be more valuable than one without a metamodel.

And the moment you start thinking at a meta level, then you’re moving into a higher level of abstraction.  In this higher level, you will have a greater opportunity to describe your intentions agnostic of the reference architecture and the vendor’s technology stack.

The way I see it, services are defined at a meta level.  They describe your intentions and are independent of a reference architecture.  However, if you chose a reference architecture up front, then describe your intentions in the vocabulary of the reference architecture.

Does this make sense?  Because I’m just hypothesising here.