A DBA suggested that I read up on "Practical API Design: Confessions of a
Java Framework Architect".
Apparently the DBA had
read the phrase "direct compiler support of versioning of APIs" in a
review of the book and -- immediately -- become terribly confused.
can see why a DBA would be confused. From a DBA's point of view all
data, all processing and all management-- all of it -- is intimately
tied to a single tool. The idea behind Big Relational is to
conflate configuration management, quality assurance, programming and
the persistent data so that the product is inescapable.
idea is so pervasive that not using the RDBMS has to be called a
"movement", as in "NoSQL Movement". It's not a new idea -- it's old
wine in new bottles
-- but Big Relational has become so pervasive
that avoiding the database makes some folks feel like renegades.]
to the confusion is the reality that DBA's live in a world where
version management is difficult. What is an API version number when
applied to the database? Can a table have a version? Can a schema have
[IMO, the answer is yes, database
designs -- metadata -- can easily be versioned. There's no support in
the database product. But it's easy to do with simple naming
For a DBA -- who's mind-set is
often twisted into "one product hegemony" and "versioning is hard" --
the phrase "direct compiler support of versioning of APIs" maps to
"direct tool/database/everything support of versioning." Nirvana.
Things in Moderation
A relevant quote from
the book is much more sensible than this fragment of a review. "Some
parts of the solution should be in the compiler, or at least reflected
in the sources, and processed by some annotation processor later."
versioning is not a good idea for adding to a programming language. At
all. It's entirely a management discipline. There's no sensible
avenue for "language" support of versioning. It can make sense to carry
version information in the source, via annotations or comments. But to
augment a language to support management can't work out well in the
1. Programming Languages are Turing Complete. And Nothing More.
Syntactic sugar is okay, if it can be proven to be built on the Turing
complete core language. Extra "features" like version control are well
outside the minimal set of features required to be Turing complete. So
far outside that they make a completeness proof hard because there's
this extra stuff that doesn't matter to the proof.
Don't Add Features. The language is the language. Add features
via a toolset or a annotation processor or somewhere else. Your API
revision junk will only make the proof of completeness that much more
complex; and the proof won't touch the "features".
2. Today's Management Practice is Only A Fad. Version numbering
for API's with a string of Major.Minor.Release.Patch
is simply a trendy fad. No one seems to have a consistent
understanding of what those numbers mean. Further, some tools
(like subversion) simply using monotonically increasing numbers -- no
Someday, someone will come up with an
XML Feature Summary (XFS) for describing features and aspects of the the
API, and numbers will be dropped as uselessly vague and replaced with a
complex namespace of features and feature enumeration and a URI
referencing an RDF that identifies the feature set. Numbers will be
replaced with URI's.
Canonize Today's Management Practice in the Language. When the
current practice has faded from memory, we don't want to have to retool
our programming languages.
What To Do?
we do for API version control is -- well -- hard work. Annotations
are good. A tool that scrapes out the annotations to create a "profile"
of the API might be handy.
In Python (and
other dynamic languages) it's a much simpler problem than it is in
static languages like Java and C++. Indeed, API version management may
be one of the reasons for the slow shift from static to dynamic
If we try to fold in complex
language features for API version support, we introduce bugs and
problems. Then -- when management practice drifts to a new way of
handling API's -- we're stuck with bad language features. We can't
simply deprecate them, we have to find a new language that has similar
syntax, but lacks the old-bad API management features.
has a nice "Requires", "Provides" and "Obsoletes" specification that's
part of the installation script. This is a handy level of automation:
the unit of configuration management (the module) is identified at a
high level using simple numbers. More than this is probably
And -- of course -- this isn't
part of the Python language. It's just a tool.