RE: [xsl] Converting CSV to XML without hardcoding schema details in xs

Hi Nathan,

Thanks a lot for your help. I was just trying to exhaust the XSL route. It
seemed to be a really good one for us, considering that we may need to
transform CSV's (with differing schemas) into corresponding XML's i.e. the
schema of one xml would differ from that of another.

> From Michael's email, it seems like that may be doable - but may need more
reading on the regex stuff.

I will also look into what you have suggested.

Thanks,

Vish.

> -----Original Message-----
> From: Nathan Young -X (natyoung - Artizen at Cisco)
> [mailto:natyoung(_at_)cisco(_dot_)com]
> Sent: Monday, June 26, 2006 11:02 AM
> To: xsl-list(_at_)lists(_dot_)mulberrytech(_dot_)com
> Subject: RE: [xsl] Converting CSV to XML without hardcoding schema details
> in xsl
>
> Hi.
>
> I don't know how you need to treat performance but regular expressions
> are going to be a lot slower than the low level css parsing routines you
> can get by using a perl, java or c library someone wrote to parse csv.
> These are cleverly written and perform very well, a quick web search for
> your language will turn up useful links if you go this route.
>
> If "good enough" is good enough for you performance-wise, regular
> expressions probably can work for you.  If you do pursue this I strongly
> recommend an application called "regex coach" for troubleshooting and
> learning regular expressions.  It really makes the effects of your
> expression visible to you and lets you quickly adjust and try
> variations.
>
> ----->Nathan
>
> > > > There's a lot of potential backtracking here: it might be
> > better to
> > > > replace each "(.*)," with "[^,]*" or with "(.*?),".
> > > [Pantvaidya, Vishwajit] Does "[^,]*" work the same as "(.*),"
> > > - I understand that ^ is start of line metachar. How does the
> > > former match the alphabet chars?
> > No, within square brackets, ^ means "not". So [^,]* matches a
> > sequence of
> > any characters except comma.
> >
> > The problem with your expression is that (.*) matches as many
> > characters as
> > it can. Then it sees ",", so it backtracks to find the last
> > comma. Then it
> > sees the next (.*), and has to backtrack again; and so on.
> > > > My own instinct would be to use something like:
> > > >
> > > > ([^"]*,|"[^"]*",)*
> > > [Pantvaidya, Vishwajit] Oxygen would not accept this regex as
> > > "it matches a zero-length string".
> > Perhaps then you want to change the final "*" to a "+".
> >
> > > Anyway, how does this regex work - it does not seem to have
> > > anything that matches the alphabet chars.
> > See above: [^"] matches everything except quotes.
> >
> > > And does the ,|" match comma or double quotes - because
> > > actually some field will have both.
> > The first alternative, [^"]*, matches any field that ends
> > with a comma, and
> > doesn't contain a quotation mark. The second alternative,
> > "[^"]*,", matches
> > any field that begins and ends with quotes (followed by a
> > comma), and might
> > contain a comma between the quotes.
> >
> > It's very hard to find out what the exact rules for CSV files
> > used by a
> > particular product are: for example, how it represents a
> > field that contains
> > quotation marks as well as commas. (That's one of the great
> > advantages of
> > XML< you can find a specification!) If you know the exact
> > rules for your
> > particular flavour of CSV, you can adapt the regex to match
> > (well, you can
> > if you study a bit more about regular expressions).
> > > Maybe this conversion is easier done with some Java code.
> > I'm sure it can be done using regular expressions but it
> > looks as if you
> > need to do some learning in this area.
> >
> > Michael Kay
> > http://www.saxonica.com/
> >
> >
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