4.2.2.1 Note: A question of flexibility 

The main issue, which informed the design of multishop.php, is that almost anything can 

be  encoded  in  the  HTTP  query  string  passed  into  it.  Unlike  a  typical  HTTP form into 

PHP scenario, such as in the case of queries.php above, the search parameters cannot be 

predefined.  

This  is  because  we  need  to  be  able  to  describe  and  search  for  an  infinite  number  of 

different products and services, which can be described in an infinite number of different 

ways. For example, a computer shop`s inventory and description thereof differs radically 

from an art gallery`s, or a butcher`s or a bookshop`s. A typical item in a computer shop 

might be: 

  DESCRIPTION:mouse; MAKE:Samsung; MODEL:SM937 Optical; PRICE:24.99. 

A pet shop, whereas, describes its mice in a completely different way: 

  DESCRIPTION:mouse;  GENUS SPECIES:   Mus  musculus ;  NAME:  Mickey; 

COLOUR:white; PRICE 24.99. 

Creating set categories for every type of product and service on sale in the country would 

be  completely  impractical,  so  it  was  decided  instead  to  make  the  system  as  flexible  as 

possible.  Critically,  this  rules  out  the  use  of  DTDs,  something  which  would  seem  to 

negate  a  basic  rule  of  XML,  namely  that  all  documents  be  strictly  structured.  As 

explained above, however, it would be nigh on impossible to define and formalise all of 

the tags and permitted attribute values for every possible item that the system is likely to 

come across. 

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