Sunday, August 29, 2010

I was interviewed for
PrintMediaCentr by Deborah Corn on the topic of JDF (Job Definition Format).

As more and more print production tasks are becoming controlled by connected multi-vendor systems, we need a common, standards based language that enables these system to 'talk'.

JDF is an instance of XML. JDF is designed to carry a print job from genesis through completion. This includes a detailed description of the creative, prepress, press, postpress and delivery processes.

Several people have asked me "what is XML ?"

XML is a rule book about how a computer language needs to "be".

When a computer talks with another computer, there needs to be a language. Like any language, we need nouns and verbs, we need adjectives too.

Here is an example;


At first glance this is both hard to read and to hard to fully understand unless we add a few things like spaces and punctuation.

i put coffee table very hot

That is a little better - but without syntax and other important bits we use in language rules, it is still not easily understood. Now, if we add all that stuff...

I put (your) coffee (on the) table (and it's) very hot.

I is the noun, Put is the verb, Your is a pronoun, Coffee is yet another Table is a noun, Very is an adverb and Hot is an adjective - get the picture ? We need rules to make this make sense.

In an XML laungage, we needed to include these rules inside a message, you might express these rules as tags.

< verb > Put < pronoun > Your < noun > Coffee etc...

You may have been able to assume a few things because we are humans and we have 'context' - we may have had a conversation about you wanting some coffee, and you might even guess which table I am speaking about, but even if you guessed wrong, you can walk around and find it...

In the computer to computer world, we do not have the luxury of context or assumptions.

EVERYTHING must be spelled out.

We can't have unanswered questions like "Is the coffee in a cup ? Which table ? Is there a cream and sugar available ? If so, where ? Are there spoons and napkins ?

You can see - you need very specific things for very specific tasks.

Besides language structure -
JDF has a Glossary

Something as simple as a PayPal payment becomes quite complex because it is not just your computer and my computer that needs to communicate, it is several other computers and systems that need to not just listen but respond.

That is what XML enables.

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