Two types of Architects

I am amused by these creatures called 'Architects' in software development. In recent phenomena, They are available under numerous headings such as 'Software architect', 'Solution architect', 'Front end architect', 'Enterprise architect' and so on. To me, in what they really do, there are only two broad types of architects. My brain timed out while guessing fancy names for them so their description is in order with uninteresting machine generated type names, it is up to you to decide what to call them.

The Type1 Architect:
A Type1 architect lives near 'The well of Eternal dreams' in his tranquility. He speaks high of latest technologies, buzzwords from internet meme. He actively attends all expensive technology conferences, management meetings, and is excellent at presenting management with summaries of what he may possibly be capable of.
The ideal Type1 architect rarely talks to developer and/or QA teams, he doesn't really waste his time for trivial details and is religious about development-by-exception (don't stop coding/testing till you hit the roadblock); he would rather express his greatness with another Type1 architect who can really appreciate him. He is a huge fan of his super-mega automated, ultra-modern cloud-based, universally-ultimate end-of-the-world web 9000.0 ready architecture, which he thoughtfully insists in applying wherever it's not needed. His thinking is beyond languages, frameworks, platforms and business needs, no mortal can grasp what he thinks. He usually masters the skill of overkill and is full of without-the-box ideas. I can really go on for next few weeks talking about this type of architects but I need to talk about the other type so I will stop here.

The Type2 Architect:
This type of dude is a very simple earthliving guy, he lives by the belief that success of software development efforts is dependent only on the people who are involved in it rather than tools and technologies. He holds the shared vision of what the end product is likely to be and thrives at driving the team efforts in that direction without managing them. He doesn't fear coding (more like the existing code fears for its life when he starts coding), testing or training whenever he needs to do it. He believes in pleasing management with frequent stable releases than presentation of the obvious. He communicates with everyone, right from tester to business analysts and managers frequently, this guy is often found roaming around discussing with different team members.

So if you are an architect, what type are you?

Formal grammars, parsing etc. for dummies

I thought it may be useful to post summaries of what I have been reading recently. In this post, I will try to explain some basic grammar and parsing stuff in as simple way as I can (omitting all the academic complacency) .

A grammar defines a language with a set of rules of type x -> y, where x is left hand side of the rule and y is right hand side of the rule. x and y can be either expandable or literals depending on grammar type (math zealot? read terminals and non-terminals).

Chomsky hierarchy defines four levels of grammar (although these are not the only grammar types in literature but Chomsky is cool dude in linguistic literature, hence the list):

0. Unrestricted grammar:

Languages based on such grammar can have any rule for derivation (which usually means any text can belong to a possible unrestricted grammar like 'yo dawg', where 'yo dawg -> u'). However, it is possible to define a language with unrestricted grammar which is also Turing complete. A language based on unrestricted grammar is extremely difficult to parse, but not completely impossible. Such language doesn't necessarily make sense, e.g. It is possible to create a math expression such as this 1++1=1--*1=1 in an unrestricted language, as well as an unrestricted English statement such as this: "all your bases are belong to us".

1. Context sensitive grammar:

A language defined with CSG may represent all the natural languages. Such grammar is defined with a set of rules where both sides may have expandable symbols (e.g. "a" B "c" -> "a" "x" "c"). It is very difficult to build a parser which can parse CSG.

2. Context free grammar:

All programming language grammars are context free grammars. It can have only one expandable symbol on left hand side of a grammar rule and is very easy to parse. E.g. X -> "if" (y) z | "if" (y) z "else" (X), where y and z can be represented as other statements of the same grammar. There are several well known parsing techniques to parse CFGs such as:

- LL(1)-LL(k) with a recursive descent parser (top down parsers with look-aheads 1 to k) and,
- Bottom up parsers such as LR(1) and LALR which can parse more CFGs than LL parsers (generally shift reduce parsers).

LL parser starts with Left to right and always expands Left expandable symbol first (think of queue) where as LR starts with Left to right but expands Right symbol first (think of stack).

3. Regular grammar:

A regular expression is a language defined by a regular grammar. It is represented as X -> "t" | "t" Y, where Y represents expandable symbol and always follows literal (if it exists). E.g. ab*, where * may be an expandable symbol defined to mean one or more occurrence of the literal it followed as a grammar rule.

Each grammar type above is a subset of previous grammar type, meaning every regular grammar is context free grammar, every context free grammar is also context sensitive grammar and so on.

Mutual recursion fun with Eclipse Debug model

I rarely come across real-world data structures which are inherently mutually recursive (a.k.a. Daisy chain recursion in CS literature). Recently, while writing a plug-in related to eclipse.debug, I came across this interesting data structure.

Source Eclipse.org

Observe the IVariable ←→ IValue relationship (although most relationships in this object-model is mutually recursive), given an implementation of this model (say JDI) how do you clone an object-tree representing variables on a stack-frame?

The answer is simple: assuming implementation classes Variable and Value just write a simple function to clone variables one by one:

public class Variable {
…
private Value value;
…
public static Variable create(IVariable var) {
  Variable v = new Variable() ;
  try {
      v.setName(var.getName());
      v.setType(var.getReferenceTypeName());
      v.setValue(Value.create(var.getValue()));
      return v;
  } catch (DebugException e) {
      ..
  }
}
}

Similarly for Value class:

public class Value {
…
private  Variable[] variables;
…
public static Value create(IValue var) {
    Value v = new Value() ;
    try {
        v.setType(var.getReferenceTypeName());
        v.setValue(...);
        IVariable[] variables = value.getVariables();
        if (variables != null) {
            for (IVariable variable : variables)
                v.add(Variable.create(variable));
        }
        return v;
    } catch (DebugException e) {
        ..
    }
}
}

Statement 'Variable.create(yourJDIVariable);' clones entire JDI object. This is one of those intuitive recursion examples which you die to find out IRL. Interesting, isn't it?

This is how your regular stack-frame looks (Variables view):

And this is how it looks when you represent it using an example debug model :

Introducing PyConsole!

I have been pretty inactive this year, unlike what I planned (yawn, haven't heard from DLTK since June either) . I started learning Python earlier this year and felt the need of an embedded python shell inside Eclipse. This was something PyDev is missing [Edit: Simone pointed out that PyDev already has this neat feature, I was late to discover it] as compared to other python tools in Linux such as Eric. So I decided to write one.

PyConsole is direct result of my irregular and intermittent Eclipse development (lately), it's very simple plug-in with a basic exploit of Eclipse Console View and manages two way synchronized I/O from the python interpreter process controlled by a background Eclipse job. It provides few basic features anyone might expect from a shell such as syntax highlighting, command history etc.

Here's the code repository if anyone would like to check it out. If you have suggestions or feedback please write to me or create a bug.