TDT4252 Modelling of Information Systems Advanced Course

Transcription

1 1 TDT4252 Modelling of Information Systems Advanced Course Sobah Abbas Petersen Adjunct Associate Professor

2 2 Overview of lecture today Process Modelling: IDEF0 and BPMN Based on the following article: Vernadat, F. B. (1996), Chapter 4: Modelling Functional Aspects, in Enterprise Modelling and Integration: Principles and Applications. Chapman and Hall. ISBN: Noran, Ovidiu, S. Business Modelling: UML vs. IDEF, Griffiths University, Menzel, Christopher, Mayer, Richard J. The IDEF Family of Languages. (pages 1-11 only) A07: Stephen A. White, Introduction to BPMN, BPTrends, July

3 3 From lecture on perspectives to conceptual modelling Structural Functional Behavioral Rule-oriented Object-oriented Social communication Actor/role-oriented Perspectives of an enterprise

4 4 Functional Modelling Methods to model the functional aspects of an enterprise: the things to be done and the way things are done in an enterprise. The purpose of a functional modelling approach is to describe the enterprise functionality and enterprise behaviour to the level of detail required by business users. Ref: Vernadat, 1996

5 5 Enterprise Functionality Concerns the things to be done, i.e. activities and operations performed, either by humans or machines, within an enterprise. Enterprise functionality represents actions performed in the form of functions transforming input into output, over a period of time. Ref: Vernadat, 1996

6 6 Enterprise Behaviour Concerns flow of control within an enterprise, i.e. the sequence in which things are done. Enterprise behaviour governs the way enterprise functionality is performed according to occurrences of enterprise states and real-world events. Ref: Vernadat, 1996

7 7 Functional Modelling Methods Most functional modelling methods are based on a functional decomposition principle: functions of the system modelled are decomposed into sub-functions, sub-functions into sub-functions, and so on. Functions can be activities or processes. Functions are then connected by means of a precedence relationship to model the business processes of the enterprise. Ref: Vernadat, 1996

8 8 Terminology: Activity and Process Activity: An activity f performs something, usually transforming its inputs into outputs. Generally, this transformation may happen if some condition C is verified. Activity f transforms an input state into an output state, under condition C. Process: Processes are logico-temporal sequences of activities. They are partially ordered sets of activities. Task: a part of a set of actions for completion. Ref: Vernadat, 1996

9 9 Taxonomy of Manufacturing Enterprise Activities Design Production Control Production Engineering Manufacturing Production Planning Preliminary design Inventory control Process planning Machining and assembly activities Long-term forecasting Detailed design Master production scheduling Manufacturing plant layout design Process control Master production scheduling Engineering design/ analysis Material requirements planning Part programming Quality control Material requirements planning Documentation Production scheduling Scheduling Tool and fixture design Planning Production scheduling Ref: Vernadat, 1996

10 10 Business Processes A business process is a collection of related, structured activities or tasks that produce a specific service or product (serve a particular goal) for a particular customer or customers. (Ref: Wikipedia) A business process is a sequence (or partially ordered set) of enterprise activities, execution of which is triggered by some event and will result in some observable or quantifiable result. (Ref: Vernadat, 1996) Goal Think as processes instead of functions and procedures!

11 11 Business Processes Modelling Business Process Models take into account the business goals, business structure and the resources that are available to achieve the business goals. This introduces additional concepts to the ones introduced in functional modelling: input transformed into output, under a specific condition. Business Goals Resources As-is To-be

12 12 History Flow charts Control flow diagrams Gantt Charts Pert charts SADT/IDEF UML (Unified Modelling Language) BPMN (Business Process Modelling Notation)

13 13 SADT SADT: Structured Analysis Design Technique (Ross 1977, Ross and Schoman 1977) Originally developed as a system-blueprinting method for software engineering, i.e. a method for detailed requirements definition. Main strength: it is based on a structured methodology for decomposing complex systems into functions and sub-functions. - Not suitable for describing flows (it describes dependencies). - Only provides a static snapshot of the state of the system.

14 14 IDEF Languages (1) ICAM (Integrated Computer Aided Manufacturing) IDEF = ICAM DEFinition Language Originated in the 1970s, in the US Air Force and the ICAM program, based on SADT. Initially intended for use in Systems Engineering IDEF0 : for activity modelling or functional modelling. Later a suite of languages: IDEF1, IDEF2 for more advanced modelling. We will focus on IDEF0!

15 15 IDEF0 IDEF0 : for activity modelling or functional modelling. Models the decisions, actions and activities of an organisation or system, in order to communicate the functional perspective of a system.

16 16 IDEF0: Syntax A model of a function at the highest level of inputs, outputs, controls and mechanisms. ICOMs Inputs Controls Function Mechanisms Outputs Inputs: items that trigger or are transformed in the activity Controls: guide or regulate the activity Mechanisms: resources used to perform the activity Outputs: results of the activity or items processed or transformed

17 17 IDEF0: Decomposition The top level is called a context.

18 18 IDEF0: ICOMs Input: Can be a trigger Input that is transformed to output. Control Guide or regulate activity!!! Distinction between input and control: inputs change, controls remain unchaged. Mechanism: resources needed to perform activity People Equipment, IT Financial resources Outputs Results of a performing the activity

19 19 IDEF0: Dependency & Flow Dependency: One process depends on another. Flow: something flows between processes: Information, material Remember the Barings Bank case?

20 20 IDEF0 Model in Metis (1)

21 21 IDEF0 Model in Metis (2) Role of ICOMs

22 22 IDEF0 Model in Metis (3) The ICOMs show their relevance to the processes. They can be considered in more detail as other domains.

23 23 IDEF0 Model in Metis (4)

24 24 IDEF0 Modelling in Metis Use MEAF template From Model Tree view, select: Metis Enterprise Architecture Framework Process Domain Use Modelling Objects: Process (object), Process Input (interface), Process Control(interface), Process Output (interface), Process Mechanism (interface) To link processes via the ICOMs, use the menu process modelling menu, available on the process and ICOM objects: Point to a process or an ICOM Click right mouse button, a list of possible relationships appear Select appropriate relationship

25 25 Connecting IDEF0 ICOMs to Other Domains in Metis To link ICOMs to other domains in the model : Select the desired object (e.g. a document) Point to an ICOM Click right mouse button, a list of possible relationships appear Select appropriate relationship

26 26 IDEF0: Benefits Supports understanding of the organisation Helps improve our knowledge about the organisation Supports decision making Supports planning and improvement (e.g. by adding new processes easily)

27 27 IDEF0: Strengths & Weaknesses Strenghts: Effective in detailing the system activities for function modelling. Provide a concise description of systems, by using the ICOMs (Input, Control, Mechanism, Mechanism) The hierarchical nature allows the system to be easily refined into greater detail. Weaknesses: Can be so concise that only domain experts can understand. Can be misinterpreted as representing a sequence of activities.

28 28 IDEF and UML IDEF Comes from manufacturing Addresses business environments Aims to cover O-O, knowledge representation and software development UML O-O software Driven by software development Focussed on designing software systems UML business customisations are based upon principles borrowed from IDEF.

29 29 Discussion: IDEF0 Is IDEF0 functional modelling or Process Modelling or both? How can you use IDEF0 in your assignment? How does IDEF0 link to the other modelling methods and languages we have looked at?

30 30 BPMN: Introduction BPMN: Business Process Modelling Notation First specification released in May Defines a Business Process Diagram (BPD), which is based on a flowcharting technique tailored for creating graphical models of business operations. Business Process Model: a network of graphical objects, which are activities, and the flow controls that define their order of performance.

31 31 BPMN: Aim To create a simple mechanism for creating business process models, while at the same time being able to handle the complexity inherent to business processes. Simple: use familiar notation Categories of Notations Flow Objects Connecting Objects Swimlanes Artifacts

32 32 BPMN: Flow Objects Set of core elements Event: something that happens during the course of a business process. Denoted by circles Affect the flow of the process: e.g. a trigger or a result. Activity: Generic term for work that is performed. Can be atomic (task and sub-processes) or non-atomic (compound). Gateway: Used to control the convergence and divergence of sequence flow: decisions and forking.

33 33 BPMN: Connecting Objects Flow objects are connected together in a diagram to create a basic skeletal structure of a business process. Sequence flow: shows the order or sequence that activities will be performed in a process. Message Flow: shows the flow of messages between two separate process participants. Association: associates data, text and other artifacts with flow objects. Shows the inputs and outputs of activities.

34 34 Example: Discussion

35 35 BPMN: Swimlanes A mechanism to organise activities into separate visual categories in order to illustrate different functional capabilities or responsibilities. A graphical container for a participant s activities. Pool: A participant in a process. Name Lane: A sub-partition within a pool and will extend the entire length of the pool. Name Name Name

36 36 BPMN: Artifacts Allows some flexibility in extending the basic notation. Data object: a mechanism to show how data is required or produces by activities. They are connected through associations. Group: Can be used for documentation or analysis purposes, but does affect the sequence flow. Annotation: mechanism for a modeller to provide additional text in the model. Text

37 37 Example: Discussion

38 38 BPMN: General Uses Collaboration, B2B (Business to Business) When there is a collaboration between two or more organisational entities. Swimlanes are used for this. Shows clear resposibilities. Internal purposes Detailed business process models: flow, sequences, decisions, events, etc.

39 39 BPMN: Strenghts & Weaknesses Strenghts: Connects business process representations with system design Represents a more unified modelling language than some of its predecessors Weaknesses: Difficult to model teamwork where the line of responsibility is not so clear. Focussed towards process execution.

40 40 Discussion: BPMN How does BPMN compare to IDEF0? How does BPMN link to the other modelling methods and languages we have looked at? How can you use BPMN in your assignment? When should we use which method?

41 41 Next Lecture Product Modelling Product Modelling in Metis Friday, 25 February 2011, room F4 There will be an opportunity to talk about the assignment.