I personally would try to use the "fill-in the blanks" design principle --
as much as possible:
<DateOfPublication>
<Year>$$(substring($Published, 1, 4))</Year>
<Month> $$(substring($Published, 5, 2))</Month>
<Day> $$(substring($Published, 7, 2))</Day>
</DateOfPublication>
The above is (a fragment of) a separate XML document, and will be one of
the inputs of the transformation that fills-in the blanks and produces the
final result.
Thanks,
Dimitre
On Thu, Apr 21, 2022 at 9:36 AM Roger L Costello costello(_at_)mitre(_dot_)org <
xsl-list-service(_at_)lists(_dot_)mulberrytech(_dot_)com> wrote:
Hi Folks,
I have fallen into the trap of creating my own little mapping language and
then writing an interpreter for my little language. I am hoping you can
help me out of this trap and show me how to replace my little language with
XSLT and use an XSLT processor.
Here's the background:
I am tasked to create a document which shows the mapping between one XML
vocabulary and another. In addition, I need to implement a tool that
performs the mapping, i.e., the tool takes an instance of the source XML
vocabulary and generates an instance of the destination XML vocabulary,
using the mapping document:
(source document, mapping document) --> tool --> destination document
Let's take a simple example.
The source XML vocabulary has an element whose value is a date (YYYYMMDD):
<Published>20220421</Published>
The destination XML vocabulary has three elements, one containing a year
(YYYY), a second containing a month (MM), and a third containing a day
(DD). The three elements are enclosed within an element:
<DateOfPublication>
<Year>2022</Year>
<Month>04</Month>
<Day>21</Day>
</DateOfPublication>
The mapping document must record that characters 1-4 of Published maps to
the Year element in DateOfPublication, characters 5-6 maps to the Month
element, and characters 7-8 maps to the Day element.
Remember, in addition to the mapping document I need to write a tool that
processes the mapping document to auto-generate a destination document. So
in my mapping document I provide machine-processable instructions to the
tool on how to perform the mapping:
<mapping>
<row>
<destination-element>DateOfPublication/Year</destination-element>
<source-element>Published</source-element>
<appinfo>
<substring>
<start>1</start>
<length>4</length>
</substring>
</appinfo>
</row>
<row>
<destination-element> DateOfPublication/Month</destination-element>
<source-element>Published</source-element>
<appinfo>
<substring>
<start>5</start>
<length>2</length>
</substring>
</appinfo>
</row>
<row>
<destination-element> DateOfPublication/Day</destination-element>
<source-element>Published</source-element>
<appinfo>
<substring>
<start>7</start>
<length>2</length>
</substring>
</appinfo>
</row>
</mapping>
"What's that appinfo element?" you ask. The appinfo element informs the
tool how to do the mapping. For example, this appinfo:
<appinfo>
<substring>
<start>1</start>
<length>4</length>
</substring>
</appinfo>
informs the tool: get a substring of the source element (Published)
starting at character 1 for a length of 4 and use it as the value of the
destination element (DateOfPublication/Year).
That is a little language that I made up. The tool must be implemented to
interpret my little language.
Ugh!
It would be better if I didn't invent a language.
It would be nice if I could use XSLT to express both the mapping as well
as code for doing the mapping.
I could write an XSLT program like this:
<xsl:template match="/">
<DateOfPublication>
<Year><xsl:value-of select="substring($source/Published, 1,
4)"/></Year>
<Month><xsl:value-of select="substring($source/Published, 5,
2)"/></Month>
<Day><xsl:value-of select="substring($source/Published, 7,
2)"/></Day>
</DateOfPublication>
</xsl:template>
But that's even worse than my mapping approach. Why? Because now the
mapping is buried in code. My clients don't understand XSLT. At least my
clients can understand my mapping (they ignore the appinfo part).
You might suggest, "Well, keep the mapping document (discard the appinfo
part) and supplement it with the above XSLT program. That's even more
worse. It has the mapping repeated in two places - in my mapping document
and in XSLT code.
What I want is something like this:
<mapping>
<row>
<destination-element>DateOfPublication/Year</destination-element>
<source-element>Published</source-element>
<appinfo>
<Year>
<!-- XSLT code that maps characters 1-4 of Published to
DateOfPublication/Year -->
</Year>
</appinfo>
</row>
...
When I "run" that document, all the XSLT snippets get executed (by an XSLT
processor).
Well, I think that's what would be really good, but I seek your
suggestions. How to create a declarative mapping document with embedded
XSLT commands?
/Roger
--
Cheers,
Dimitre Novatchev
---------------------------------------
Truly great madness cannot be achieved without significant intelligence.
---------------------------------------
To invent, you need a good imagination and a pile of junk
-------------------------------------
Never fight an inanimate object
-------------------------------------
To avoid situations in which you might make mistakes may be the
biggest mistake of all
------------------------------------
Quality means doing it right when no one is looking.
-------------------------------------
You've achieved success in your field when you don't know whether what
you're doing is work or play
-------------------------------------
To achieve the impossible dream, try going to sleep.
-------------------------------------
Facts do not cease to exist because they are ignored.
-------------------------------------
Typing monkeys will write all Shakespeare's works in 200yrs.Will they write
all patents, too? :)
-------------------------------------
Sanity is madness put to good use.
-------------------------------------
I finally figured out the only reason to be alive is to enjoy it.
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