IMS 5024 Lecture 31 IMS 5024 Process Modelling

IMS 5024 Lecture 32 Content Group assignment Class assignment Nature of process modelling Abstraction Tools/Techniques used in process modelling Place in ISD Evaluation of process modelling Reading list

IMS 5024 Lecture 33 Class assignment What is this about? What conventions/rules are used? What does it depict? Where would this fit into ISD?

IMS 5024 Lecture 34 Process modelling help us to grasp: Inputs Outputs Processing Relationship between processes

IMS 5024 Lecture 35 Abstraction Def: Stripping and idea or system of its concrete and physical features (Avison et. Al.) Show essence!! Level of abstraction –High –Low

IMS 5024 Lecture 36 Levels of DFD’s Context DFD Decomposition diagram Overview DFD (system DFD) Middle level DFD Primitive level DFD Link to other techniques?

IMS 5024 Lecture 37 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

IMS 5024 Lecture 38 Tools used Data flow diagrams Decomposition diagram Data Dictionary Structured English Decision Tables Decision Trees

IMS 5024 Lecture 39 Symbols Process Internal/external entity Data store Data flow

IMS 5024 Lecture 310 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

IMS 5024 Lecture 311 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

IMS 5024 Lecture 312 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

IMS 5024 Lecture 313 Decision Trees wholesale customer retail customer local item imported item Determine Customer Discount 15% 10% 12% 7%

IMS 5024 Lecture 314 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

IMS 5024 Lecture 315 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

IMS 5024 Lecture 316 Context diagram Levelling DFDs Diagram 3 (level 1) Level zero diagram Diagram 3 (level 1) Further diagrams or process descriptions

IMS 5024 Lecture 317 Different levels of modelling Conceptual level – Not confuse with conceptual modelling of data Logical level Physical level Where does DFD’s fit into this?

IMS 5024 Lecture 318 Deliverables for process modelling is used Old New Physical Logical

IMS 5024 Lecture 319 Verification of the model Walkthroughs with user Verify for: –Missing algorithms –Logical verification –Syntax Checking –Tracing data elements –Cross referencing –Tracing obejctives

IMS 5024 Lecture 320 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

IMS 5024 Lecture 321 Thinking in Process modelling Hard Vs Soft ?? Perspective –Objective vs Subjective –Nature of the organisation

IMS 5024 Lecture 322 Advantages of Process modelling  a well-known process modelling 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

IMS 5024 Lecture 323 Disadvantages Focus on processes – need to know a lot to get a good understanding Miss key aspects of the data Others??

IMS 5024 Lecture 324 Process modelling view of ISD Development group Objectives Environment Object system Object system Change process Hirschheim et al see reading list

IMS 5024 Lecture 325 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., A taxonomy of Software development Methods. Communications of the ACM, Vol37, No11

IMS 5024 Lecture 326 Reading for next week McFadden, F.R.; Hoffer, F.R; Prescott, M.B. (1999). Modern Database Managemetn. Fifth Edition. Addison Wesley, USA. Chapter 3 and 4.