.SH Overview of the Game Driver.
.LP
If all you want to do is play with the supplied game and never get
your paws dirty now is a good time to stop. I'm going to assume
some basic understanding of programming and related ideas. Since this
manual is so dire that you'll probably need to explore the source code
to figure out what on earth is really going on I don't think that is
too unfair.
.LP
The original goal of AberMUD5 was that everything in the database would
be a 'thing' and have the same basic behaviour. In actual fact there are
several differently behaving sets of things within the AberMUD system.
.LP
Firstly there are words. A word is a set of letters, a value and a type.
The sole purpose of the value is to identify synonyms. Any words with
the same type and value are synonyms. 
The game parser understands quite a wide variety of words, although
only within a limited command oriented structure. The syntax is best
described as
.LP
sentence :== verb {item} {preposition} {item} | verb {text}
.br
		 | verb {item} {preposition} {text}
.br
item:== {ordinate} itemphrase
.br
itemphrase:== adjective {itemphrase} | noun
.SP 1
.LP
The different word types are:
.SP 1
.IP verb: 15
Normal command sentences begin with a verb. The parser doesn't
understand the English structure 'use item to verb target'. 
Verb numbers 0-12 are reserved for directions, and 13-199 for
game editing commands.
.IP adjective: 15
An adjective qualifies a noun to define exactly which item
is being referred to. An item can only have one adjective
associated with it in the current system. The game allows
adjectives and nouns with the same text, and correctly
interprets them.
.IP noun: 15
Each item within the game has a noun it is associated with. 
Nouns may be further qualified by adjectives.
.IP ordinate: 15
An ordinate is used as the final level of qualification of
a specific item. An ordinate secifies which of the matching
set of items is to be used by number - eg fourth blue sack.
.IP preposition: 15
As far as the game system is concered a preposition is
any linking word that seperates two items within the
command given. For example 'to' 'in' and 'from'.
.IP pronoun: 15
Words like 'him' and 'her'. The game system tracks and manages
the basic English pronouns :- him, her, it, them, there, me.
When processing the parser substitutes back in the appropriate
item for the words.
.LP
Although these are a tiny subset of the language structure and the parser
is easily fooled into interpreting things that would never be said in real
English, it is more than adequate for the job, and more powerful than most
other game system parsers.
.LP
The game has some limits however. Firstly it is unable to handle the structure
use <item> to <verb> <target>. This can be handled easily within the database
as we shall see later. Its two much more real limits are the inability to
handle <verb> <"string"> <preposition> <item> - for example say "hello" to 
eric, and the ability to handle sentences of the form <verb> <nounitem1> 
<item2>, where the noun of item1 is also possibly an adjective. When a 
preposition is used the parser is cable of handling the second example. 
The first case is a deliberate choice. To process say "hello" to eric, you would
have to include the quotes. It was felt the ability to avoid quotes outweighed
the advantages of handling this sentence form.
.LP
The second type of thing within the database we have almost met already. When
the parser resolves an adjective noun to give something which exists in the 
game world, it is resolving it to an item, the next in our three types.
.LP
An item represents some physical or at least metaphysical entity within the game
world. Unlike many game systems it makes no seperation between the different
basic types , instead each of these types can be attached to the basic item. By
working in this fashion game designers get maximum flexibility and ease of use,
since they never have to worry 'is this a player or a room', and in addition
an item can be two or more of the types. We shall look in detail at items in the
next chapter.
.LP
The final type has to do with the result of someone typing in a command. Something
has to explain what the game does when this command is entered This is the role
of the database tables. These are sections of game code describing conditions
and testing and changing the status of items. It is these which allow the author
to control and customise his world.
.LP
A couple of minor types also float around the game system. The only one of note
is the BSX picture, which is a picture for Bram Stolks BSX graphics system.