[erlang-questions] Glossary

Dave Pawson <>
Mon Jul 20 10:28:39 CEST 2009


2009/7/20 Richard Andrews <>:
> On Mon, Jul 20, 2009 at 5:52 PM, Dave Pawson<> wrote:
>> New to Erlang. Just reading the new O'Reilly book (very good btw).
>> I'm a little unsure on terminology.
>
> I'll have a go...

erlang.org/doc/glossary.html does it. I'm sure Maxim could have
been more sarcastic though.

>
>
>> Node
>
> It's an operating system process. A virtual machine which contains
> processes. Large systems off consist of several nodes distributed
> across many hosts for redundancy, load balancing or some other reason.
> Processes can send messages between themselves across nodes and across
> hosts (network transparent message passing).

Node = (approx) a single processor/computer/machine?
That's how I had it.  Then one of those is 'the erlang node', i.e. where
whole programs are started from.



>
>> Process
>
> A light-weight state machine with a mailbox for receiving messages
> from other processes or system IO resources. In java you might know
> them as green threads. The node schedules processes to run when there
> is something for them to do (like a message in the mailbox).

This seems the key bit. Yet least natural to get hold of.
Receiving messages is a key part.
Is it true that a process is generally a single module ('a chunk of code')?
Even if code from other modules is used?
And what's the relationship between scheduling, the VM and processes/modules?



>
>> Resource
>
> Memory, socket, etc.
> Internally might also refer to some erlang specific bits and pieces
> like atoms and binaries (which you'll get to).

Less understood here. I guess resource is a bit vague!
>From the glossary:

Resource
    The actual resource to be managed. A resource is represented by a
Managed Object. Each resource is mapped to one or several resources.

which isn't much better/clearer.

>
>> Task
>
> Ambiguous. Need context. This isn't an erlang-specific term I know.

The book doesn't have it indexed, I'll put that one down to 'a
computing task to be executed'
i.e. book specific :-) I wasn't sure if it was Erlang based.


>
>> Event
>
> Usually this means a message that was delivered to a process mailbox.

Thanks. That's how I had it.

Tks Richard.


regards



-- 
Dave Pawson
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