RE: [xml-dev] RE: Markup Combinators -- A Functional Approach to XML

["Cox, Bruce" <Bruce.Cox@USPTO.GOV>]

I agree with Piotr, it makes me very uneasy to see what I'd have considered content used as element names.  No harm in using XML syntax to create a financial calculator, but it no longer reads like XML, to me.  When my colleagues and I set out to model business concepts and practices in a schema, we take some care to separate business vocabulary from the values associated with what amount to variables in the vocabulary.  For example, "Applicant" or "Claim," either of which can take on numerous values.  The complexity of the vocabulary (as others have said in this chain) is proportional to the complexity of the business.  Yes, of course we can simplify it, but at the great risk of losing sufficient transparency for the customer.  If it doesn't look, smell, taste right, they won't buy it.  Of course, I'm as fascinated by the allure of pure, abstract systems as the next geek.  Maybe, after I retire, I'll get to actually work with one.

Bruce B Cox
OCIO/AED/Software Architecture and Engineering Division
571-272-9004


-----Original Message-----
From: Piotr Bański [mailto:bansp@o2.pl] 
Sent: 2011 December 17, Saturday 10:59
To: xml-dev@lists.xml.org
Subject: Re: [xml-dev] RE: Markup Combinators -- A Functional Approach to XML

Hi Roger,

I'm not sure I get the idea: what if the contract is worth not "one" but
1.32 USD (etc.)? Do you then create integer-based element names? (I fear to ask about reals :-))

This reminds me of something that felt deeply wrong to me when I saw it, but I felt unable to pin the problem down in one sentence: I once saw grammatical markup that used the values of grammatical categories not as attribute or element content, but rather as element names.

Technically doable, assuming a closed set of values, and straightforwardly constrainable even with DTDs, and yet it simply felt wrong to see something like:

<entry>
<noun>car</noun>
<def>...</def>
</entry>

instead of, e.g.,

<entry>
<form>car</form>
<gram>noun</gram>
<def>...</def>
</entry>

I feel a need to keep the container skeleton apart from data values, with data type info preferably separated as well, but it's more like an instinct, and I'd be happy to tack a reference of two to it. Or to hear why it's possibly just one of many valid alternatives.

I hope this is on topic wrt your original thought and query.

Best,

  Piotr

On 17/12/11 15:04, Costello, Roger L. wrote:
> Hi Folks,
> 
>  
> 
> I noticed several typos in my previous message. They are fixed (below).
> 
>  
> 
> I am excited about the markup combinator functional approach to XML -- 
> create a small set of primitive markup combinators and use them to 
> create complex combinators. It occurs to me that this is also the 
> approach used in mathematics -- start with a small set of axioms and 
> use them to create theorems.
> 
>  
> 
> Do you know of an XML vocabulary that was created using this markup 
> combinator functional approach? If yes, would you briefly describe the 
> set of primitive combinators and a few of the complex combinators that 
> were created from the primitive combinators?
> 
>  
> 
> /Roger
> 
>  
> 
> ----------------------------------------------------------------
> 
> The following example is inspired by “/How to write a financial 
> contract/” by Simon Peyton Jones. [2] Many of the words come from that 
> paper.
> 
> *Example: Use Markup Combinators to Create Financial Contracts *
> 
> The finance industry has an enormous vocabulary of jargon for typical 
> combinations of financial contracts (swaps, futures, caps, floors, 
> swaptions, spreads, straddles, captions, European options, American 
> options, ..., the list goes on.) Treating these individually is like 
> having a large catalog of prefabricated components. The trouble is 
> that someone will soon want a contract that is not in the catalog.
> 
> If, instead, we could define each of these contracts using a fixed, 
> precisely specified set of combinators, we would be in a much better 
> position than having a fixed catalog. For a start, it becomes much 
> easier to describe new, unforeseen, contracts. Beyond that, we can 
> systematically analyze, manipulate, and perform computations over 
> these new contracts, because they are described in terms of a fixed, 
> well-understood set of primitives.
> 
> Let us begin with some simple combinators and then use them to create 
> more complex combinators.
> 
> Here is a simple financial contract, it pays one USD at the time of 
> acquisition
> 
> <one>USD</one>
> 
> The recipient receives one USD.
> 
> “one” is a combinator. It is a contract.
> 
> For our next contract the recipient again acquires the value 
> immediately, except all the payments are multiplied by (scaled up) 100 
> times
> 
> <scale><konst>100</konst><one>USD</one></scale>
> 
> The contract pays 100 USD.
> 
> “scale” is a combinator. It is a contract.
> 
> To re-emphasize, this new contract was created by assembling a double 
> with another contract.
> 
> The recipients of the previous two contracts received the value 
> immediately. We can create a contract that is worthless until a 
> Boolean condition becomes true. Let’s create this contract
> 
> When at January 1, 2012, acquire one USD
> 
> Here’s the contract
> 
> <when>
>       <at>2012-01-01</at>
>       <one>USD</one>
> </when>
> 
> The “when” combinator consists of a Boolean observable and contract.
> Here are a couple examples to illustrate what a Boolean observable is:
> 
> Hey, I observe that the date is (not) now 2012-01-01.
> 
> Hey, I observe that the temperature is (not) now
> 5 degrees Celsius.
> 
> “at” is a Boolean observable that becomes true at time /t/.
> 
> Now let’s create a contract that is known in the industry as a 
> zero-coupon discount bond (zcb). Let’s create this zcb contract
> 
> Receive 100 USD on January 1, 2012.
> 
> This is easily created by assembling the above combinators.
> 
> A zcb contract is created by assembling a date, double, and currency.
> The below XML creates the desired zcb contract. Read the XML as 
> follows
> 
> This contract pays off when at January 1, 2012, an amount equaling the 
> scaling 100x of one USD.
> 
> Here is the XML
> 
> <zcb>
>     <when>
>            <at>2012-01-01</at>
>           <scale><konst>100</konst><one>USD</one></scale>
>      </when>
> </zcb>
> 
> Why did we go to the trouble of defining zcb in terms of multiple 
> combinators rather than making it primitive? Because it turns out that 
> scale, when, and one are all independently useful. Each embodies a 
> distinct piece of functionality, and by separating them we 
> significantly simplify the semantics and enrich the algebra of contracts.
> 
> *Recap*: the above discussion illustrates how to approach XML in a 
> functional manner; that is, how to create XML by assembling markup 
> combinators. This is beautiful markup. This functional approach to XML 
> is consistent with XSLT and NVDL.
> 
> /Roger
> 
> [1] http://lists.xml.org/archives/xml-dev/201107/msg00116.html
> 
> [2]
> http://research.microsoft.com/en-us/um/people/simonpj/papers/financial
> -contracts/contracts-icfp.htm
> 
>  
>