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Appendix D.

PDL Syntax

This chapter introduces the syntax for the Persistence Deﬁnition Language.

D.1. PDL Grammar

The following is an Extended Backus-Naur Form (EBNF) grammar that deﬁnes the current PDL

language. EBNF is a standard notation for formally deﬁning a language that extends BNF (they are

functionally equivalent -- EBNF simply introduces some elements for better readability).

In this grammar, items within angle braces

ITEM are terminals (tokens), while

those not within angle brackets are non-terminals. If you are unfamiliar with EBNF,

http://www.garshol.priv.no/download/text/bnf.html is a good starting point.

/** Top level constructs. */

file :=

model <SEMI>

( pdl_import <SEMI> )*

( object_type | association | data_operation )*

<EOF>

model := <MODEL> idpath

pdl_import := <IMPORT> idpath ( <DOT> <STAR> )?

object_type :=

( <VERSIONED> )?

( <QUERY> | <OBJECTTYPE> ) id

( ( <EXTENDS> type |

<CLASS> javaClass <ADAPTER> javaClass |

<RETURNS> <INT> <DOT> <DOT> ( id | <INT> ) ) )?

<LBRACE> ( statement )* <RBRACE>

association :=

<ASSOCIATION> <LBRACE> property <SEMI> property <SEMI>

( property <SEMI> )*

( option_block )?

( event )* <RBRACE>

data_operation :=

<DATA_OPERATION> id <LBRACE> ( option_block )? sql_block <RBRACE>

/** First level constructs. */

statement := ( simple_statement <SEMI> | compound_statement )

simple_statement :=

( property_stmt | object_key | reference_key |

unique_key | aggressive_load | join_stmt )

compound_statement := ( event | option_block )

/** Simple statements */

property_stmt := property

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Red Hat Web Application Framework 6.1 Manual do Utilizador Página 203