README.md

		# Overview

		-Relational XPath Map (RXM) is a terse database query language that
		-produces structured documents using a [BNF Converter](http://bnfc.digitalgrammars.com/).
		+Relational XPath Map (rxm) is a simple, terse database query language
		+that produces structured documents.
		+
		+The syntax examples show how to produce an XML document, but the same
		+mapping could produce any structured format (e.g., JSON, YAML, or TOML).
		+
		+# Syntax
		+
		+This section describes the rxm language syntax. The syntax entails a map
		+and a where clause.
		+
		+## Map
		+
		+The element mapping consists primarily of a database entity on the left
		+and a simple XPath expression on the right.

		```
		-root > people, # "root" is a keyword
		+root > people, # "root" keyword starts the document
		person > person, # maps a node to table context
		.first_name > first, # maps a node to column
		.last_name > name/last, # maps an ancestor node to a column
		.age > @age, # @ maps an attribute to table node
		account.person_id > person.person_id, # performs an inner join
		account > account, # context is now "account" node
		.id > @id,
		-^, # return to previous context
		+^, # pop stack to previous context
		address > address,
		.; # globs all columns. ; is WHERE
		```

		-# Namespaces
		+This would produce a document structure similar to the following:

		```
		-root > people(html, http://www.w3.org/TR/html4/),
		-person > html:person,
		-
		-person.id > people:id( people, http://www.people.com ),
		+<people>
		+ <person age="42">
		+ <first>Charles</first>
		+ <name>
		+ <last>Goldfarb</last>
		+ </name>
		+ <account id="123"/>
		+ <address>
		+ <street>123 Query Lane</street>
		+ <city>San Francisco</city>
		+ </address>
		+ </person>
		+</people>
		```

		-# Where clause
		+Note: Multiple stack pops (`^`) are allowed per line. If a pop would otherwise
		+exceed the root context, the context remains at the root.
		+
		+## Where

		```

		account.id <= 42 # numeric less than or equal to comparison
		account.id >= 42 # numeric greater than or equal to comparison
		+```
		+
		+## Namespace
		+
		+```
		+root > people(html, http://www.w3.org/TR/html4/),
		+person > html:person,
		+
		+person.id > people:id( people, http://www.people.com ),
		```
		+
		+# Requirements
		+
		+The software requirements include:
		+
		+* [Java 8](http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html)
		+* [BNF Converter](http://bnfc.digitalgrammars.com/) (see the [BNFC documentation](https://bnfc.readthedocs.org/en/latest/lbnf.html) for details)
		+
		+# Rationale
		+
		+The reasons to create rxm include:
		+
		+* Decouple SQL statements from document output format.
		+* Eliminate repetitious code.
		+* Provide a database-agnostic mechanism to generate structured documents
		+(currently based on SQL/XML).
		+* Few databases are fully compliant with SQL/XML:2006.
		+* XQuery has limited open-source implementations for major RDBMS software.
		+
		+# Addendum
		+
		+It might be possible to reuse maps for bidirectional data loading in addition
		+to data extraction.

Added explanation for the example.

Author	Dave Jarvis <email>
Date	2015-02-08 12:11:06 GMT-0800
Commit	7d0726d49fdb590aa4fc0e7b3fcc988b019b114a
Parent	40ecb3f
Delta	67 lines added, 10 lines removed, 57-line increase