1. CS 501: Software Engineering Fall 1999
Lecture 8
Formal Specification II

2. Administration
Assignment 2:
Instructions for submitting Assignment 2

3. Schemas Schema:  The basic unit of formal specification.
 Describes admissible states and operations of a system.

4. LibSys: An Example of Z Library system:  Stock of books
 Registered users.
 Each copy of a book has a unique identifier.
 Some books on loan; other books on shelves available for loan.
 Maximum number of books that any user may have on loan.

5. LibSys: Operations  Issue a copy of a book to a reader.
 Reader return a book.
 Add a copy to the stock.
 Remove a copy from the stock.
 Inquire which books are on loan to a reader.
 Inquire which readers has a particular copy of a book.
 Register a new reader.
 Cancel a reader's registration.

6. LibSys Level of Detail: Assume given sets: Copy, Book, Reader
Global constant:
maxloans

7. Domain and Range ran m X dom m Y y x m : X Y
dom m = { x  X :  y  Y  x y}
ran m = { y  Y :  x  X  x y}

8. LibSys: Schema for Abstract States
Library
stock : Copy Book
issued : Copy Reader
shelved : F Copy
readers: F Reader
shelved  dom issued = dom stock
shelved  dom issued = Ø
ran issued  readers
r : readers • #(issued  {r}) maxloans
<

9. Schema Inclusion LibDB stock : Copy Book readers: F Reader LibLoans
issued : Copy Reader
shelved : F Copy
r : Reader • #(issued  {r}) maxloans
shelved  dom issued = Ø
<

10. Schema Inclusion (continued)
Library
LibDB
LibLoans
dom stock = shelved  dom issued
ran issued  readers

11. Schemas Describing Operations
Naming conventions for objects:
Before: plain variables, e.g., r
After: with appended dash, e.g., r'
Input: with appended ?, e.g., r?
Output: with appended !, e.g., r!

12. Operation: Issue a Book
 Inputs: copy c?, reader r?
 Copy must be shelved initially: c?  shelved
 Reader must be registered: r?  readers
 Reader must have less than maximum number of books on loan:
#(issued  {r?}) < maxloans
 Copy must be recorded as issued to the reader:
issued' = issued  {c? r?}
 The stock and the set of registered readers are unchanged:
stock' = stock; readers' = readers

13. Operation: Issue a Book
stock, stock' : Copy Book
issued, issued' : Copy Reader
shelved, shelved': F Copy
readers, readers' : F Reader
c?: Copy; r? :Reader
[See next slide]

14. Operation: Issue a Book (continued)
[See previous slide]
shelved  dom issued = dom stock
shelved'  dom issued' = dom stock'
shelved  dom issued = Ø; shelved'  dom issued' = Ø
ran issued  readers; ran issued'  readers'
r : readers  #(issued  {r}) maxloans
r : readers'  #(issued'  {r}) maxloans
c?  shelved; r?  readers; #(issued  {r?}) < maxloans
issued' = issued  {c? r?}
stock' = stock; readers' = readers
<
<

15. Schema Decoration Issue Library Library' c? : Copy; r? : Reader
c?  shelved; r?  readers
#(issued  {r?}) < maxloans
issued' = issued  {c? r?}
stock' = stock; readers' = readers

16. Schema Decoration Issue Library c? : Copy; r? : Reader
c?  shelved; r?  readers
#(issued  {r?}) < maxloans
issued' = issued  {c? r?}
stock' = stock; readers' = readers

17. The Schema Calculus Schema inclusion Schema decoration
Schema disjunction:
AddCopy AddKnownTitle  AddNewTitle
Schema conjunction:
AddCopy EnterNewCopy  AddCopyAdmin
Schema negation
Schema composition = ^ = ^

18. Requirements Definition and Analysis
System and
Software design
Implementation
and Unit Testing
Integration and
System Testing
Operation and
Maintenance

19. The Requirements Process
Feasibility
Study
Requirements
Analysis
Requirements
Definition
Requirements
Specification
Feasibility
Report
System
Models
Definition of
Requirements
Requirements
Document
Specification of
Requirements