Data and Knowledge Representation Lecture 6 Qing Zeng, Ph.D.

Last Time We Talked About UMLS UMLS

Today We Will Talk About Process Process Finite state machine Finite state machine Flow chart Flow chart Petri Net Petri Net

Process Object: continuant Object: continuant E.g. diagnosis, medication, data repository E.g. diagnosis, medication, data repository Process: occurrent Process: occurrent E.g. diagnose, treat, retrieve E.g. diagnose, treat, retrieve

Describing Process Predicate logic Predicate logic treat (Dr. Jones, Ms. List) treat (Dr. Jones, Ms. List) Frame-based system Frame-based system Patient Frame has a slot “primary care” or “attending physician” Patient Frame has a slot “primary care” or “attending physician” There are more about “treat” to specify There are more about “treat” to specify When, where, how, why, what result When, where, how, why, what result

Types of Process Process Continuous Process Discrete Process Initiation Continuation Cessation Event State

Example Continuous Process Continuous Process Aging Aging Discrete Process Discrete Process Out patient visit (make appointment, check in with nurse, see a doctor, have test/receive medication) Out patient visit (make appointment, check in with nurse, see a doctor, have test/receive medication)

Basic Distinctions Discrete or continuous Discrete or continuous Linear or branching Linear or branching Independent or ramified Independent or ramified Immediate or delayed Immediate or delayed Sequential or concurrent Sequential or concurrent Predictable or surprising Predictable or surprising

Basic Distinctions Normal or equinomral Normal or equinomral Flat or hierarchical Flat or hierarchical Timeless or time-bound Timeless or time-bound Forgetful or memory-bound Forgetful or memory-bound

Process, Procedure and History Sequence of events and state Sequence of events and state Process: one event or state is current Process: one event or state is current Procedure: abstract (pattern or script of processes) Procedure: abstract (pattern or script of processes) History: record of a past process History: record of a past process

Finite State Machine (FSM) Discrete process (continuous process can be simulated with fine time steps) Discrete process (continuous process can be simulated with fine time steps) State transition diagram State transition diagram Formal Definition: Formal Definition: A finite set of states: Q A finite set of states: Q A finite set of inputs: I A finite set of inputs: I A transition function F(Q, I) -> Q, F can be a partial Function A transition function F(Q, I) -> Q, F can be a partial Function

FSM Basic components: state (circle), transition (arrow), input (label on the arrow) Basic components: state (circle), transition (arrow), input (label on the arrow) End state can be marked with double circles End state can be marked with double circles

Suspect DB Confirmed DB Highly suspect DB High blood sugar in test 1 High blood sugar in test 2 No DB normal blood sugar in test 1 normal blood sugar in test 2 FSM

Flow Chart Event (box) and decision (diamond) Event (box) and decision (diamond) Arrow (transition) and label on the arrow (condition for decision) Arrow (transition) and label on the arrow (condition for decision) Start and end can be specified with double box Start and end can be specified with double box

Petri Net A finite set of places (circle) A finite set of places (circle) A finite set of transactions (line) A finite set of transactions (line) A finite set of arrows connecting either places to transactions or transactions to places A finite set of arrows connecting either places to transactions or transactions to places

Petri Net Petri Net Marking: assign a non-negative integer to each place. (dot/token) Marking: assign a non-negative integer to each place. (dot/token) Firing: a transaction take place after enabled Firing: a transaction take place after enabled Firing sequence: the sequence of transaction firings for a given PN with a given initial marking Firing sequence: the sequence of transaction firings for a given PN with a given initial marking

Petri Net Conflict Conflict Starvation Starvation Deadlock Deadlock

Petri Net Assign values to tokens Assign values to tokens Define functions for transaction Define functions for transaction Specify scheduling policies Specify scheduling policies Timed Petri Net Timed Petri Net

Exercise Overweight patients should be instructed either excise regularly or keep a healthy diet for 3 months. When one fails, try both for 3 months. When both fail, a patient should be given medication x for 2 months.

Reading Sowa Chap. 3 Sowa Chap. 3