Semantics of ARIS Model

Transcription

1 Semantics of ARIS Model Why is Semantics Important? Jon Atle Gulla An analysis of the ARIS ing language with respect to - conceptual foundation and - formal properties Green, P. and M. Rosemann: An Ontological Analysis of Integrated Process Modeling van der Aalst, W. M. P.: Formalization and Verification of Event-Driven Process Chains 1 Conceptual is the bridge between customer and project domain experts and analysts analysts and designers/programmers people and CASE environments project and end-users [contract] [requirements] [system documentation] [source of analysis] [training documentation] 2 Outline I. ARIS Conceptual Model ARIS ing ARIS conceptual Interpretation of ARIS s Analysis with respect to ontological foundation BWW ontological Mapping of ARIS to BWW ontological Formalization of ARIS process (EPC) using Petri nets Formalization of EPC process Petri nets Mapping from EPC to Petri nets Verification of EPCs 3 Multi-view conceptual language for ing business processes and organizational struct ures Organizational view Function view Data view Control view (Output view) Pre-defined s for ERP functionality Low-level processes correspond to specific transactions in ERP system Organizational structures correspond to structural elements in ERP system 4 ARIS Organization view Model of organizational units and positions/employees that are important for reporting purposes, areas of responsibilities and user profiles in ERP system Organizational unit ARIS Function view Hierarchical list of manual and automated functions included in the business processes Function SCC processing Hierarchical relationship Sales Purchasing Billing Request quotation Create purchase Manager r A. Sølvberg P. Hughes Secretary H. Trætteberg Position Assign source of supply Create items Employee 5 6 ARIS and ERP Systems 1

2 ARIS Data view Structural of master data (e.g. customers, vendors, materials) and transactional data (e.g. sales s, purchase s, project WBS structures, invoices) Relationship ARIS Control view (EPC) Event (or state) Function (process) 1..* refers to 0..* decide 1 Pricing price for condition doc. Generalization Logical connector (AND, OR, XOR) 0..1 Information object Quotation Attributes and events may also be added Data elements and elements from the organizational view may also be added 7 8 Interpretation of ARIS Models II. BWW Ontological Model How to analyze semantic aspects of a conceptual? Can map to (other) formal s Can define with respect to mathematical or logical theory Can map to ontological theory of information systems Mapping to computerized system introduces implementation details that do not belong to conceptual realm Ontological BWW ontology Universe of Discourse Conceptual Computerized system Petri nets Formal Mathematics Logic 9 Introduced by Bunge, Wand and Weber Nat ure of ontological : Deep structure of information systems comprises those properties that manifest the meaning of the underlying real-world system Ontological describe and predict the impact of deep structure phenomena Components of ontological : Representation state-tracking good decomposition Purpose of ontological : Study of internal structures of information systems that are independent of implementation decisions Theoretical foundation for designing and evaluating ing languages Comparison of conceptual ing languages 10 BWW Ontological Constructs Ontological constructs for describing deep structure phenomena of information systems: Ontological Analysis of ARIS Ontologica l construct EPC view Da ta view Function view Orga nizationa l vie w Thing User, department Property Function, attribute Attribute Function, attribute Attribute Class Entity Organization Kind Generalization Generalization Organization State Event Conceivab le state space State law Function > connector > event Generalization, cardinalities Generalization Lawful state space Event Event > Function > event Process Process, function Function Conceivab le event space Transformation Function Function Lawful transformation Event > connector > function Lawful event space History Coupling Relationship System System composition Cluster Subsystem Cluster Organizational hierarchy External event Start event Stable state End event Unstable state Event > Function > Event Internal event Event > Function > Event Well-defined event Poorly defined event ARIS and ERP Systems 2

3 Ontological Weaknesses of ARIS No representation for conceivable state space, lawful state space, conceivable event space, or lawful event space Sufficient focus on identifying all important state and transformation laws may not be present No representation of system, system environment, system structure, history, acts on, unstable state, and poorly defined event Defining scope and boundaries of system may be difficult Decomposition not sufficiently supported Function view ontologically redundant III. Formalization with Petri nets NB! Do not take into consideration links to data elements or organizational elements Event-driven Process Chains (EPC) Process (control view) of ARIS Used to describe business processes Formalization of EPC syntax Mapping EPCs onto Petri nets Provides a formalization of EPC Defines the semantics of EPC Enables checks for consistency, completeness, soundness, etc The Structure of EPC Models Logical connector (AND, XOR, OR) Event Formalization of EPC Syntax EPC = (E, F, C, T, A): E is a finite set of events F is a finiste set of functions C is a finite set of logical connectors Tc C t {AND, XOR, OR} is a function which maps each connector onto a connector A ` (E%F) 4 (F%E) 4 (E%C) 4 (C%E) 4 (F%C) 4 (C%F) 4 (C%C) is a set of arcs Syntactic properties: The sets E, F, and C are pairwise disjoint For each e c E: e <= 1 and e <= 1 4 There is at least one start event and one final event Function 4 For each f c F: f = 1 and f = 1 4 For each c c C: c >= 1 and c >= 1 4 The graph induced by EPC is weakly connected 15 4 C J and C S partition C, i.e. C J 3 C S = Ø and C J 4 C S = C 4 C EF and C FE partition C i e C EF 3 C FE = Ø and C EF 4 C FE = C 16 Petri nets - Basics Petri nets - Dynamics p1 arrived t1 p2 p3 available Decide monitoring Create strategy t2 t3 purchase p4 p5 Receive t4 goods Goods p6 received Petri nets is a tuple (P, T, F): P is a finite set of places T is a finite set of transitions (P 3 T = ) F ` (P % T) 4 (T % P) is a set of arcs (flow relations) Notation: t3 = {p2, p3} p2 = {t2, t3} Place p1 is an input place for transition t1 Place p2 is an output place for transition t1 Petri nets and formalization: Petri nets have a mathematical foundation Formal semantics Automatic analysis 17 Decide monitoring strategy arrived available Create purchase Receive goods Goods received Tokens: A place contains zero or more tokens Firing rule: A transition t is said to be enabled iff each input place p of t contains at least one token An enabled transition may fire. If transition t fires, then t consumes one token from each input place p of t and produces one token in each output place p of t State M: Distribution of tokens over places M c P t N n Example: State M = p1 + 2p3 t1 is enabled, t3 is not enabled 18 ARIS and ERP Systems 3

4 Formalization of EPC Semantics Mapping of connectors Defining EPC semantics in terms of Petri nets Basic mapping of EPC to Petri nets: event place function transition Mapping of connectors more complex Depends on of connector Depends on events and/or functions linked to connector f i : function i e i : event i Mapping from EPC to Petri nets Mapping from EPC to Petri nets Verification of EPC Models An erroneous EPC (1) Regular: An EPC is regular iff EPC has two special events: estart and efinal Every node n c N is on a path from e st art to e final. Sound: A regular EPC is sound iff For every state M reachable from the initial state, there exists a firing sequence leading from state M to the final state The final state is the only state reachable from the initial state where event e final holds There are no dead functions Well-structured An EPC is well-structured iff for any pair of connectors c 1 and c 2 such that one of the nodes is is C AND and the other in C XOR and for any pair of elementary paths p 1 and p 2 leading from c 1 to c 2, a(p 1 ) 3 a(p 2 ) = {c 1,c 2 } p 1 = p 2 23 Model not sound: Assume that no billing needed event holds. Produce article will never be fired Will not hold 24 ARIS and ERP Systems 4

5 An erroneous EPC (2) Conclusions Two s to the right are not well-structured ARIS rooted in informal ing languages Semantic analysis of ARIS BWW ontological evaluation of ing language with respect to deep structure of information systems Petri nets formalization of EPC semantics by mapping EPC diagrams to Petri nets ARIS and ERP Systems 5