Simple Outline XML (SOX) is an alternative syntax used to simplify the textual representation of Extensible Markup Language (XML) documents. It is designed to be simpler, easier to read, and less verbose than standard XML while still being as machine-readable. Since it is easily parsed, a valid SOX document can easily be transformed into a valid XML document.

Standard XML syntax consists of textual data which is marked-up using markup instructions, referred to as tags. All text affected by one of these instructions is encapsulated between a start and end tag. The start tag consists of a less-than () symbol. An end tag appears at the end of the affected text, consisting of a less-than symbol, a slash (/), the instruction name, and a greater-than symbol. The following is an example of an XML document:

Basic bread Flour Yeast Warm Water Salt Mix all ingredients together, and knead thoroughly. Cover with a cloth, and leave for one hour in warm room. Knead again, place in a tin, and then bake in the oven.

Simple Outline XML uses whitespace indentation to encode some of the information ordinarily encoded using XML tags. The level of indentation makes the structure of the document immediately apparent, which eliminates the need for closing tags. Each line represents a single element, attribute, or text node which also eliminates the need for attribute quoting. Elements are represented by names ending with a greater-than symbol, attributes contain an equals (=) sign, and any other text entities are text nodes. Text may be quoted if it contains a greater-than symbol or an equals sign. The following is the SOX representation of the above XML document:

Recipe> name=bread prep_time=5 mins cook_time=3 hours title>Basic bread ingredient> amount=3 unit=cups Flour ingredient> amount=0.25 unit=ounce Yeast ingredient> amount=1.5 unit=cups Warm Water ingredient> amount=1 unit=teaspoon Salt Instructions> step>Mix all ingredients together, and knead thoroughly. step>Cover with a cloth, and leave for one hour in warm room. step>Knead again, place in a tin, and then bake in the oven.

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