[SpecGL] C1: define your terms, GP 2

2nd (and last) GP for section C1.

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Good practice: re-use existing terms, and don't redefine them

What does this mean?
When a definition for a term already exists (e.g. in a different
specification) and matches your needs, re-use the term and its
definitions without changing them, and with a reference to the source.

Why care?
Re-using existing terms reduce the cost of crafting new definitions, and
makes it easier for readers already familiar with other specifications
to get into a new one. Also, conflicting definitions of the same term
leads to a reduced interoperability.

Technique:
- use the W3C Glossary system to check if there are existing definitions
of the term you want to re-use
- when quoting a definition from another specification, put a link back
to the specification 
-- 
Dominique Hazaël-Massieux - http://www.w3.org/People/Dom/
W3C/ERCIM
mailto:dom@w3.org