1. Method of Language Definition
A Language is defined by:
A: Lexical = Valid Tokens & Words
B: Syntax = The GRAMMER of the Language
C: Semantics = The MEANING of valid syntactical statement
Language

2. 26 letter and . ? ! Special Characters
The Valid Tokens
create
“Words” - Expression
then become
Written English
26 letter and . ? ! Special Characters
Words
Obj of Preposition
Verb Clause
Sentences
Statement – Complete Statement Rules – Spelling of Words – Completing a sentence
What is part A: Lexical?
What is part B: Syntax?

3. 26 letter and . ? ! Special Characters
The Valid Tokens
“a, e, h, H, i, J, m, n,
o, s, y”
create
“Hi, John,
name, my, is”
“Words” - Expression
then become
“Hi, my name is John”
Written English
26 letter and . ? ! Special Characters
Words
Obj of Preposition
Verb Clause
Sentences
Statement – Complete Statement Rules – Spelling of Words – Completing a sentence
What is part A: Lexical?
What is part B: Syntax?

4. C. Semantics Semantics Meaning of a valid syntactical statement
Context free
Context sensitive

5. Let’s Study language First, let’s look at a programming language Java
A: Syntax
Valid Token
Alphabet & Spec. Char
Words
Class, Private, Public
Statement – if (A < B)
{B = A;}

6. Syntax Graph

7. Let’s look at another programming language
A Language is defined <N, T, S, P> where
T is a finite set of terminal symbols,
N is a finite set of non-terminal symbols,
S is the start symbol, S,
P is a finite set of production rules of the form,
Let’s see the grammar of Arithmetic expressions in the next slide. 

8. Language is defined <N, T, S, P> where
N= Non-terminal symbols:
<Exp>, <Term>, <Factor>
T= Terminal symbols:
+, -, *, /, (, ), x, y, z, ...
S= Start symbol:
<Exp>
P= Production rules:
<Exp> ::= <Exp> + <Term> |
<Exp> - <Term> |
<Term>
<Term> ::= <Term> * <Factor> |
<Term> / <Factor> |
<Factor>
<Factor> ::= x | y | ... |
( <Exp> ) |
- <Factor>
A grammar for the concrete syntax of simple arithmetic expressions

9. Semantics “The MEANING of a correct …
If A + 2 > B then A = 10;
Logic that decomposes to “machine activity”
Register
ACU

10. Think! Possible expressions: Registering Log in Search Find home
Your Project
Possible expressions:
Registering
Log in
Search
Find home
For Log in
Mouse Travel
define : 1) Tokens = Mouse Selection
Ind. on screen Obj.
Mult. On screen Obj.
valid expressions Words
Define criteria

11. Possible tokens in your interaction Language
MT : Mouse Travel
MS: Mouse Selection
– indicate the on screen object
Mult: Multiple Selection
multiple screen objects selected
 Alph + Specific (except + ENTER TAB)
S: String

12. Example Goal - Login A valid syntactical login:
MT => Click when on B1
=> Type “bernal”
=> Tab
=> Type “SHhh”
=> Enter P1 B1 B2 B3