From: Jatinder Singh <jatinder.saundh@...>
Date: 2006-06-15T02:26:49+09:00
Subject: Using YAML as a data DSL

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I have an RoR application which has various GUI screens for taking input
from users for creating some entities in my application.
What ever information is given by the user I am putting in to a
datastructure in ruby(I have created a set of classes in ruby for that
purpose),

To give you an example say there is a Music store and there are various
records of various artists available.
we can have following classes for storing the information entered by user
for records and artists,
class Record

@name
#array for storing objects of artist class
@artists

end
class Artist
@name
@phone
end

Note: ofcourse we can use a db here and update the info entered by user
directly in the database, but may be I am giving a wrong example here,
actually the above information about entities is entered by user only once.

Now I want to give the end user, a way to circumvent GUI and directly write
in to a file the information about the entities in a format specified by
me(thats what a DSL is all about).
Following is what I intend to have with respect to DSL

1. This DSL would be more of a data DSL then a business DSL which is meant
for defining business rules.
2. It should be user friendly(who doesn't want a DSL to be user friendly)

with these goals in mind I wrote an internal DSL(having ruby method calls)
and wrote some code which populates above mentioned classes(Record and
Artist).

I worked in other direction of using YAML as DSL; for that I created a YAML
compliant file with following contents,
###########################
--- !ruby/object:Video
artist: Jatinder
name: SampleVideo
type: Pop
###########################
YAML provides a way to persist objects in text format which is I believe
very user friendly, so what I thought is that a user can create a file with
above contents and then use YAML::load method to load above file's content
in to ruby object.
Well in this case I really dont have to do much, as in I dont have to write
a parser.

There might be several deficiencies/probelms in the 2nd approach, few of
them I think are,
1. YAML has a strict format, even if a ":" goes here and there then the
whole file goes for a toss.
2. In the above file, I would definately not like to have
"!ruby/object"..can I override that somehow?(ofcourse I can have a layer
between YAML and file, which modifies the file to change the file
structure/contents to make it YAML compliant).
3. is YAML stable enough? I read about syck..it seems to solve the problem
of solving perf issues.


Any thought's on above appraoch?

Regards,
Jatinder

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