[MarkLogic Dev General] Type safe data and referencing questions

[Danny Sokolsky]

Hi Mark,

I will take a stab at your questions.

1) You do not need a schema to use typed data.  A schema will make it so
Mark Logic treats an element or attribute as its defined type without an
explicit cast, but you can always add an explicit cast (like the
use-case example) to make sure XQuery treats a value as a certain type
(with or without a schema).  The schema just makes that a little easier.
There might be some performance advantage to using a schema, but I don't
think it will be that big.  It is worth trying though, as this might
depend somewhat on your content.  The real performance advantage will
come from creating range indexes on elements or attributes you will use
in comparisons.  Schemas can also help you ensure that your data is in
the correct format when you load it, as Mark Logic will throw an
exception if it cannot cast content in an element or attribute to the
type specified in the schema. 

2) You could put the referencing information in the properties document.
The default conversion application in CPF does this, for example, to
keep track of the original documents and various converted documents.

3) There are no foreign key constraints built in.  I think any best
practices would depend on what you are trying to do.  Two approaches
that tend to work well are to a) put the constraining items in the same
document and/or b) use the properties document corresponding to a
document to store information about what is in the document.  

-Danny

-----Original Message-----
From: general-bounces at developer.marklogic.com
[mailto:general-bounces at developer.marklogic.com] On Behalf Of Mark
Waschkowski
Sent: Monday, January 14, 2008 1:25 PM
To: general at developer.marklogic.com
Subject: [MarkLogic Dev General] Type safe data and referencing
questions

Hi,

Have been using Marklogic for a while now and haven't seen answers to
the below questions yet, anyone know of an answer or two?

1) Type safe data -  I'm concerned with retrieval of typed data,
especially for date information. The only way to store typed data is
through the use of a schema right? I can't specify the type of data on
a per element basis, correct? ie. <person> <birthday
xs:date>01-01-1970</birthday></person>

As well, I noticed the below query in the use case examples:

 let $item := doc("items.xml")//item_tuple
              [end_date >= xs:date("1999-03-01")
               and
               end_date <= xs:date("1999-03-31")]
 return
 <item_count>
 {
   count($item)
 }
 </item_count>

Is there a schema behind the loaded data or are the examples un-type
safe? Should I just not worry about type safety and convert the data
values to the type I need when querying? If so, won't that be a
performance issue?

2) Referencing - what is the (if there is one) best practice approach
to reference documents together?
ie. Document A and Document B should both refer to Document C

3) Foreign key constraints - is this supported at all in some fashion?
If not, any approaches to suggest?

Thanks in advance for any and all suggestions!

Mark
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