1. IMS 5024 Semester 2, 2002 Lecture 3 1 IMS 5024 Process Modelling

2. IMS 5024 Semester 2, 2002 Lecture 3 2 Content Hand in Synopsis Class assignment Nature of process modelling Abstraction Tools/Techniques used in process modelling Place in ISD Evaluation of process modelling Reading list

3. IMS 5024 Semester 2, 2002 Lecture 3 3 Class assignment What is this about? What conventions/rules are used? What does it depict? Where would this fit into ISD?

4. IMS 5024 Semester 2, 2002 Lecture 3 4 Process modelling help us to grasp: Inputs Outputs Processing Relationship between processes

5. IMS 5024 Semester 2, 2002 Lecture 3 5 Abstraction Def: Stripping and idea or system of its concrete and physical features (Avison et. Al.) Show essence!! Level of abstraction –High –Low

6. IMS 5024 Semester 2, 2002 Lecture 3 6 Levels of DFD’s Context DFD Decomposition diagram Overview DFD (system DFD) Middle level DFD Primitive level DFD Link to other techniques?

7. IMS 5024 Semester 2, 2002 Lecture 3 7 Example Context Diagram Inventory System Suppliers Sales Order System Warehouse sales order goods unavailable notice purchase order supplier delivery shipping slip checked supplier invoice Accounts Department goods returned

8. IMS 5024 Semester 2, 2002 Lecture 3 8 Tools used Data flow diagrams Decomposition diagram Data Dictionary Structured English Decision Tables Decision Trees

9. IMS 5024 Semester 2, 2002 Lecture 3 9 Symbols Process Internal/external entity Data store Data flow

10. IMS 5024 Semester 2, 2002 Lecture 3 10 Data dictionary entry example sales order =sales order no. + sales order date+ customer number+ [account customer cash customer]+ customer name+ customer address+ (customer telephone no) + {order item} + sales order total amount order item =item no+ item desc + item price + item qty

11. IMS 5024 Semester 2, 2002 Lecture 3 11 Accept sales-order Find customer-details If customer-details not found Then reject sales-order Else Create sales-order-header Do while more sales-order-items find item-details calculate sales-order-item price = item price *order- qty Endo Authorise sales-order Endif Example Structured English

12. IMS 5024 Semester 2, 2002 Lecture 3 12 Example Decision Table avg account bal > $1,000 overdraft amount < $50,000 previous paid-out loan approve conditional approval reject YYYYN N Y Y N N YY N N Y N Y N YN Y N X X X X X X X

13. IMS 5024 Semester 2, 2002 Lecture 3 13 Decision Trees wholesale customer retail customer local item imported item Determine Customer Discount 15% 10% 12% 7%

14. IMS 5024 Semester 2, 2002 Lecture 3 14 Example Function Decomposition Diagram ABC Sales System 1. Sell Products 2. Manage Inventory 3. Control Finance 2.1 Deliver Product 2.2 Accept Delivery 2.3 Check Stock levels

15. IMS 5024 Semester 2, 2002 Lecture 3 15 Rules to guide the modelling Levelling – two ways ExpandExplode Balancing Naming conventions Always input and output No direct dataflow between data store and entity Number of processes on a level Numbering conventions

16. IMS 5024 Semester 2, 2002 Lecture 3 16 Context diagram Levelling DFDs 3.1 3.2 Diagram 3 (level 1) 1 2 3 Level zero diagram 2.1 2.2 Diagram 3 (level 1) Further diagrams or process descriptions

17. IMS 5024 Semester 2, 2002 Lecture 3 17 Different levels of modelling Conceptual level – Not confuse with conceptual modelling of data Logical level Physical level Where does DFD’s fit into this?

18. IMS 5024 Semester 2, 2002 Lecture 3 18 Deliverables for process modelling is used Old New Physical Logical 1 2 3 4

19. IMS 5024 Semester 2, 2002 Lecture 3 19 Validation of the model Walkthroughs with user Validate for: –Missing algorithms –Logical verification –Syntax Checking –Tracing data elements –Cross referencing –Tracing objectives

20. IMS 5024 Semester 2, 2002 Lecture 3 20 Reality of ISD Conceptual models Formal Models Application domain Implementation domain Blum, I., 1994. A taxonomy of Software development Methods. Communications of the ACM, Vol37, No11

21. IMS 5024 Semester 2, 2002 Lecture 3 21 Evaluation of Process modelling Problem orientedProduct oriented Concep- tual Structured analysis Entity relationship modelling Logical construction of systems Modern structured analysis Object oriented analysis Structured design Object oriented design Formal PSL/PSA JSD VDM Levels of abstraction Stepwise refinement Proof of correctness Data abstraction JSP Object oriented programming

22. IMS 5024 Semester 2, 2002 Lecture 3 22 Thinking in Process modelling Hard Vs Soft ?? Perspective –Objective vs Subjective –Nature of the organisation

23. IMS 5024 Semester 2, 2002 Lecture 3 23 Advantages of Process modelling  a well-known process modelling ISD technique  easily understood  a good communication tool  model both manual and automated processes shows relationship between data and processes Excellent tool for logical level discussions Supported by a number of CASE tools

24. IMS 5024 Semester 2, 2002 Lecture 3 24 Disadvantages Focus on processes – need to know a lot to get a good understanding Miss key aspects of the data Others??

25. IMS 5024 Semester 2, 2002 Lecture 3 25 Process modelling view of ISD Development group Objectives Environment Object system Object system Change process Hirschheim et al see reading list

26. IMS 5024 Semester 2, 2002 Lecture 3 26 Classification of methods Problem orientedProduct oriented Concep- tual Structured analysis Entity relationship modelling Logical construction of systems Modern structured analysis Object oriented analysis Structured design Object oriented design Formal PSL/PSA JSD VDM Levels of abstraction Stepwise refinement Proof of correctness Data abstraction JSP Object oriented programming Blum, I., 1994. A taxonomy of Software development Methods. Communications of the ACM, Vol37, No11

27. IMS 5024 Semester 2, 2002 Lecture 3 27 Reading for next week Simsion, G. (1994). Data modeling essentials: Analysis, Design, and Innovation. Van Nostrand Reinhold, USA. Chapter 2, 7 and 10.