Re: What is the logic of storing XML in a Database?

On Mar 28, 10:51 am, "Cimode" <cim...@xxxxxxxxxxx> wrote:

I should have asked the question differently. In what does XML allow
validation? I thought XML was supposed to be used for transport?

Fair enough, reasonable question. If it was purely a transport
format, the only thing that would matter was that it arrived at its
destination endpoint intact, and a CRC in a header would suffice. So
it's a little more than purely a transport format. Their life begins
a little earlier, and lasts a little longer, than their entry and exit
on the endpoints. The messages are produced and consumed by
applications that are typically very loosely coupled, often, as in the
case of ecommerce, to completely independent firms. The validation
referred to applies to the production and consumption of the messages,
or some place in the middle.

But nobody can write and sell (or give away as open source) a CSV
validator that validates an arbitrary CSV file against a standard
schema describing that CSV file, for the simple reason that no such
standard schema exists. No tools exist in this category, in contrast,
many such tools exist in the XML space.

Tools to do what again?

As an example, an XML Schema may declare that an element named
dayCountFraction is of type DayCountFraction.

<xsd:element name="dayCountFraction" type="DayCountFraction">

The type DayCountFraction may restrict the values that the field
dayCountFraction can take to a specific list, e.g. "ACT/ACT",
"30/360", "30/365".

A schema validator tool will take an XML document, apply the schema,
and will reject the message if the value is other than one in the
list.

The question should have been: what else does XML schema bring as
oppose to a header?

Well formedness. If the CSV file departs from strict name value
pairs, e.g. uses tags to distinguish different types of rows, a single
header line no longer suffices to verify that the number of values
matches the number of names. But that's a fairly trivial test
anyway. An XMLSchema will validate that a datetime in a date element
conforms to a valid ISO datetime, a code in a dayCountFraction falls
into a supported set, that the number of leg subtrees in the message
is precisely two, etc.

If you doubt the value of this, I'll just point out that a vast amount
of code in applications consuming CSV files is devoted to checking
precisley these things; they never completely trust the producer. XML
Schemas provide a standard way of expressing these rules
declaratively, once.

Do you know about XML Schema? Do you know about domains like life
insurance that standardize on a schema such as ACCORD, so that they
have a standard way of representing data?

That does not answer the question. This is a specific example of a
company that uses XML. I know many clients who totally ignore XML.

Not a company, rather an entire industry.

So you are saying that XML is more verbose than CSV right?

Yes. For example, I have a CSV file of trades (with many duplicate
fields per row) that occupies 9,884KB, and an XML file generated from
that CSV file, in a standard industry format, that occupies
34,012KB.

Regards,
Daniel Parker

.

Relevant Pages

  • Re: Interplatform (interprocess, interlanguage) communication
    ... ability of using XML to represent free-form data, ... but one can wonder what is the gain of using a schema if one is just going to use "xsd:any"?... ... well, there are some rules, but the question is more if a schema or the use of validation would offer much advantage to make using it worth the bother?... ... I think the original point though was more about XML vs S-Expressions in this case though: ...
    (comp.lang.java.programmer)
  • Re: XmlValidatingReader - just the FAQS?
    ... > read an xml file and an xsd file and validate the xml file using ... The XML schema is fine, and your instance document is valid by it, ... > Validation Error: The 'Name' element is not declared. ... The XmlSchema constructor should only appear in applications ...
    (microsoft.public.dotnet.xml)
  • Re: validating if a file is a true valid xml file that fits a cert
    ... ''' Validates an XML stream against the specified XML Schema. ... ValidateXmlFileException if the XML stream or XML Schema fails validation. ... Public Sub ValidateXmlFile(ByVal SchemaNamespace As String, ...
    (microsoft.public.dotnet.languages.vb)
  • Re: What is the logic of storing XML in a Database?
    ... proprietary schema format for flatfiles and sell a proprietary tool ... for validating a CSV file that conforms to the flat file. ... I thought XML was supposed to be used for transport? ...
    (comp.databases.theory)
  • Re: What is the logic of storing XML in a Database?
    ... I thought XML was supposed to be used for transport? ... The validation ... validator that validates an arbitrary CSV file against a standard ... schema describing that CSV file, for the simple reason that no such ...
    (comp.databases.theory)