WO2003005137A1 - Data processing - Google Patents

Data processing Download PDF

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Publication number
WO2003005137A1
WO2003005137A1 PCT/GB2002/002892 GB0202892W WO03005137A1 WO 2003005137 A1 WO2003005137 A1 WO 2003005137A1 GB 0202892 W GB0202892 W GB 0202892W WO 03005137 A1 WO03005137 A1 WO 03005137A1
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WO
WIPO (PCT)
Prior art keywords
state
state machine
parent
child
data processing
Prior art date
Application number
PCT/GB2002/002892
Other languages
French (fr)
Inventor
Raj Gawera
Joby Allen
Original Assignee
Ubinetics Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ubinetics Limited filed Critical Ubinetics Limited
Publication of WO2003005137A1 publication Critical patent/WO2003005137A1/en

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Classifications

    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F9/00—Arrangements for program control, e.g. control units
    • G06F9/06—Arrangements for program control, e.g. control units using stored programs, i.e. using an internal store of processing equipment to receive or retain programs
    • G06F9/44—Arrangements for executing specific programs
    • G06F9/448—Execution paradigms, e.g. implementations of programming paradigms
    • G06F9/4482—Procedural
    • G06F9/4484—Executing subprograms
    • G06F9/4486—Formation of subprogram jump address

Definitions

  • the invention relates to data processing and event handling.
  • the invention relates to state machines.
  • the invention provides a data processing system comprising a parent state machine and a child state machine each comprising a group of states interlinked by transitions, wherein the parent state machine comprises a parent exit state in which an appropriate event causes the execution of a parent exit transition to a state in the child state machine.
  • the invention thus provides that a state machine can be decomposed into a hierarchy of interacting state machines.
  • a complex system can be represented as a hierarchy of simpler state machines which facilitates efficient definition of the overall system.
  • the data processing system according to the invention may also be arranged such that the parent exit transition is accompanied by deactivation of the parent state machine in favour of the child state machine. This means that the data processing system's resources need only be sufficient to run either the child or the parent state machine.
  • the data processing system is arranged such that the parent exit transition is accompanied by storing of parameters defining the parent exit state used to depart the parent state machine into memory, e.g. a memory stack of the system.
  • the parameters can be stored on the C-stack.
  • the child state machine may comprise a child exit state in which an appropriate event causes the execution of a child exit transition to a state in the parent state machine.
  • the data processing system can be adapted to provide a return path to the parent state machine.
  • the child exit transition is accompanied by the deactivation of the child state machine in favour of the parent state machine, which means that the system resources need only be sufficient to run either the child or parent state machine at any one time.
  • the child exit transition is accompanied by the retrieval from a memory e.g. a memory stack, of parameters defining the parent state machine state to which the child exit transition leads.
  • the data processing system is arranged such that details of an event are saved into storage, e.g. a memory stack, if the event is not applicable to the state machine which is currently active.
  • the data processing system may also be arranged such that details of an event saved in storage may be retrieved when a state machine to which the event applies becomes active in order to allow the event to be processed. For example, if, during operation of the child state machine, an event occurs which is applicable to the parent state machine, then the details of the event can be stored until such time as the parent state machine again becomes active, at which point the details of the event can be retrieved to allow the event to be processed by the parent state machine.
  • the data processing system according to the invention may contain a hierarchy of more than two levels, i.e. more than just the "parent" and "child” levels discussed above.
  • the child state machine may itself have a child state machine, and so on.
  • the state machines in the hierarchy can be interlinked using exit transitions as discussed above.
  • Figure 1 illustrates a state machine
  • Figures 2 and 3 each illustrate a state machine implemented as a state-event matrix
  • Figures 4 and 5 each illustrate state machines linked so as to call one another.
  • the state machine of Figure 1 illustrates the simple case of an electric light operated by a push button switch.
  • the system has two states A and B, in which the light is on and off respectively.
  • the button When the button is pressed, the system toggles to the other one of its states. In other words, when the event of pressing the switch occurs, then, regardless of the current state, the "press" event triggers a transition to the other state. These transitions are indicated by the arrows in Figure 1.
  • Figure 2 illustrates how the state machine of Figure 1 can be rendered as a state-event matrix.
  • the state-event matrix of Figure 2 contains a column for each state and a row for each event.
  • the state-event matrix comprises a single row for the "press” event and two columns, one each for the A and B states.
  • the entries in the state-event matrix are populated with the necessary actions. If the current state is A, and the event is "press”, then the action is "go to state B". If the current state is B, and the event is "press”, then the action is "go to state A”.
  • Figure 3 shows how the state-event matrix can be extended to arbitrary size, using the example of n columns for n states and m rows for m events.
  • Figure 3 illustrates a state machine hierarchy according to an embodiment of the invention.
  • the state machine hierarchy is implemented using a C-type programming language and comprises a parent state machine implemented as a parent state-event matrix 12 and a child state machine implemented as a child state-event matrix 10.
  • a parent state machine is in a particular state, for example s m
  • a particular event for example e n
  • a sequence of actions are performed to call the child state machine.
  • the parameter values defining state s m are saved onto the C-stack of the system, the parent state machine is closed, the child state machine is opened and a state of the child state machine, for example s p , is nominated as the active state.
  • the active state moves around the child state event matrix 10 in accordance with whichever events occur.
  • the child state machine is in a particular state, for example s r , and a particular event, for example, e q , occurs, then the active state is transferred back to the parent state machine.
  • the child state machine is closed, the parameter values for the parent state machine are retrieved from the C-stack and the active state is assigned as the state in the parent state machine which is specified by the retrieved parameter values.
  • the parent state machine or the child state machine is active at any given time. If an event occurs which cannot be processed by the state machine which is currently active, then it is saved onto the C-stack pending the activation of a state machine to which the event applies.
  • the transitions between the state machines are shown by arrows 14 and 16.
  • Figure 5 illustrates a state macliine hierarchy according to an embodiment of the invention being used to implement a controller for configuring telecommunications transceiver equipment, such as a mobile telephone.
  • the state machine hierarchy is being used to configure a controller which works with a layered communications protocol, where inter-layer communication is achieved via signalling.
  • layer N of a protocol is a controller layer which is responsible for configuring layers N-1 and N-2 in response to external signals.
  • the parent state machine designated as an external signal handler in Figure 5 responds to the external signals by calling the layer N-1 or N-2 state machine to configure the N-1 and N-2 layers respectively.
  • the child state machines each only contain state-event actions to handle responses from their respective layers, and do not respond to external signals. Any external signals received during the execution of a child state machine are saved for processing when the child state machine exits. This ensures that the state machine implementations are "clean", i.e. they only contain transitions relevant to their purpose.

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  • Engineering & Computer Science (AREA)
  • Software Systems (AREA)
  • Theoretical Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Stored Programmes (AREA)

Abstract

A state machine hierarchy (10, 12) wherein certain states Sm, Sr contain exit transitions (14, 16) leading to other state machines. When a state machine is left in favour of another, its exit state is saved onto the C-stack. Events arising which are not applicable to the currently active state machine are saved on the C-stack.

Description

DATA PROCESSING
The invention relates to data processing and event handling. In particular, the invention relates to state machines.
According to one aspect, the invention provides a data processing system comprising a parent state machine and a child state machine each comprising a group of states interlinked by transitions, wherein the parent state machine comprises a parent exit state in which an appropriate event causes the execution of a parent exit transition to a state in the child state machine.
The invention thus provides that a state machine can be decomposed into a hierarchy of interacting state machines. For example, a complex system can be represented as a hierarchy of simpler state machines which facilitates efficient definition of the overall system.
The data processing system according to the invention may also be arranged such that the parent exit transition is accompanied by deactivation of the parent state machine in favour of the child state machine. This means that the data processing system's resources need only be sufficient to run either the child or the parent state machine.
In one embodiment, the data processing system is arranged such that the parent exit transition is accompanied by storing of parameters defining the parent exit state used to depart the parent state machine into memory, e.g. a memory stack of the system. Where the data processing system is being implemented using a C-language type system, the parameters can be stored on the C-stack.
The child state machine may comprise a child exit state in which an appropriate event causes the execution of a child exit transition to a state in the parent state machine. Thus, the data processing system can be adapted to provide a return path to the parent state machine. Preferably, the child exit transition is accompanied by the deactivation of the child state machine in favour of the parent state machine, which means that the system resources need only be sufficient to run either the child or parent state machine at any one time. Advantageously, the child exit transition is accompanied by the retrieval from a memory e.g. a memory stack, of parameters defining the parent state machine state to which the child exit transition leads.
In one embodiment, the data processing system is arranged such that details of an event are saved into storage, e.g. a memory stack, if the event is not applicable to the state machine which is currently active. The data processing system may also be arranged such that details of an event saved in storage may be retrieved when a state machine to which the event applies becomes active in order to allow the event to be processed. For example, if, during operation of the child state machine, an event occurs which is applicable to the parent state machine, then the details of the event can be stored until such time as the parent state machine again becomes active, at which point the details of the event can be retrieved to allow the event to be processed by the parent state machine.
It is possible that the data processing system according to the invention may contain a hierarchy of more than two levels, i.e. more than just the "parent" and "child" levels discussed above. For example, the child state machine may itself have a child state machine, and so on. The state machines in the hierarchy can be interlinked using exit transitions as discussed above.
By way of example only, the invention will now be described with reference to the accompanying figures, in which:
Figure 1 illustrates a state machine; and
Figures 2 and 3 each illustrate a state machine implemented as a state-event matrix; and
Figures 4 and 5 each illustrate state machines linked so as to call one another.
The state machine of Figure 1 illustrates the simple case of an electric light operated by a push button switch. The system has two states A and B, in which the light is on and off respectively. When the button is pressed, the system toggles to the other one of its states. In other words, when the event of pressing the switch occurs, then, regardless of the current state, the "press" event triggers a transition to the other state. These transitions are indicated by the arrows in Figure 1.
Figure 2 illustrates how the state machine of Figure 1 can be rendered as a state-event matrix. The state-event matrix of Figure 2 contains a column for each state and a row for each event. Hence, the state-event matrix comprises a single row for the "press" event and two columns, one each for the A and B states. The entries in the state-event matrix are populated with the necessary actions. If the current state is A, and the event is "press", then the action is "go to state B". If the current state is B, and the event is "press", then the action is "go to state A".
Figure 3 shows how the state-event matrix can be extended to arbitrary size, using the example of n columns for n states and m rows for m events.
Figure 3 illustrates a state machine hierarchy according to an embodiment of the invention. The state machine hierarchy is implemented using a C-type programming language and comprises a parent state machine implemented as a parent state-event matrix 12 and a child state machine implemented as a child state-event matrix 10. When the parent state machine is in a particular state, for example sm, and a particular event, for example en, occurs then a sequence of actions are performed to call the child state machine. The parameter values defining state sm are saved onto the C-stack of the system, the parent state machine is closed, the child state machine is opened and a state of the child state machine, for example sp, is nominated as the active state. Subsequently, the active state moves around the child state event matrix 10 in accordance with whichever events occur. When the child state machine is in a particular state, for example sr, and a particular event, for example, eq, occurs, then the active state is transferred back to the parent state machine. To achieve this transfer, the child state machine is closed, the parameter values for the parent state machine are retrieved from the C-stack and the active state is assigned as the state in the parent state machine which is specified by the retrieved parameter values. Thus, either the parent state machine or the child state machine is active at any given time. If an event occurs which cannot be processed by the state machine which is currently active, then it is saved onto the C-stack pending the activation of a state machine to which the event applies. The transitions between the state machines are shown by arrows 14 and 16.
Figure 5 illustrates a state macliine hierarchy according to an embodiment of the invention being used to implement a controller for configuring telecommunications transceiver equipment, such as a mobile telephone. The state machine hierarchy is being used to configure a controller which works with a layered communications protocol, where inter-layer communication is achieved via signalling. Consider the case where layer N of a protocol is a controller layer which is responsible for configuring layers N-1 and N-2 in response to external signals. The parent state machine, designated as an external signal handler in Figure 5, responds to the external signals by calling the layer N-1 or N-2 state machine to configure the N-1 and N-2 layers respectively. The child state machines each only contain state-event actions to handle responses from their respective layers, and do not respond to external signals. Any external signals received during the execution of a child state machine are saved for processing when the child state machine exits. This ensures that the state machine implementations are "clean", i.e. they only contain transitions relevant to their purpose.

Claims

1. A data processing system comprising a parent state machine and a child state machine each comprising a group of states interlinked by transitions, wherein the parent state macliine comprises a parent exit state in which an appropriate event causes the execution of a parent exit transition to a state in the child state machine.
2. A data processing system according to claim 1, wherein said appropriate event in said parent exit state causes the parent state machine to be deactivated.
3. A data processing system according to claim 1 or 2, wherein said appropriate event in said parent exit state causes parameters defining the parent exit state to be stored on a memory stack of the system.
4. A data processing system according to claim 1, 2 or 3, wherein the child state machine comprises a child exit state in which an appropriate event causes the execution of a child exit transition to a state in the parent state macliine.
5. A data processing system according to claim 4, wherein said appropriate event in said child exit state causes the child state machine to be deactivated.
6. A data processing system according to claim 4 or 5, wherein said appropriate event in said child exit state causes the retrieval from a memory stack of the system of parameters defining the parent state machine state to which said child exit transition leads.
7. A data processing system according to any one of claims 1 to 6, wherein an event is saved to a memory stack of the system if it is not applicable to the state machine which is currently active.
8. A data processing system according to claim 7, wherein an event stored on the memory stack is retrieved when a state machine to which it applies becomes active to allow the event to be processed by the state machine. A data processing system comprising state machines substantially as hereinbefore described with reference to Figure 4 or 5.
PCT/GB2002/002892 2001-07-02 2002-06-21 Data processing WO2003005137A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0116191.8 2001-07-02
GB0116191A GB2377285A (en) 2001-07-02 2001-07-02 State machine

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US20120282301A1 (en) * 2005-12-06 2012-11-08 Etex Corporation Porous calcium phosphate bone material

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FR2929474B1 (en) * 2008-03-28 2010-07-30 Groupe Ecoles Telecomm MULTI-LAYER HIERARCHISED COMPUTING ARCHITECTURE

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US5796752A (en) * 1995-03-06 1998-08-18 Motorola, Inc. Method and apparatus for constructing verification test sequences by euler touring a test subsequence graph
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US5796752A (en) * 1995-03-06 1998-08-18 Motorola, Inc. Method and apparatus for constructing verification test sequences by euler touring a test subsequence graph
US6052455A (en) * 1997-11-13 2000-04-18 Northern Telecom Limited Universal data structure for use with a concurrent state machine space in a telecommunications network
WO2000038022A1 (en) * 1998-12-22 2000-06-29 Varian Semiconductor Equipment Associates, Inc. Method and apparatus for controlling a system using hierarchical state machines

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Cited By (2)

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Publication number Priority date Publication date Assignee Title
US20120282301A1 (en) * 2005-12-06 2012-11-08 Etex Corporation Porous calcium phosphate bone material
US8545858B2 (en) * 2005-12-06 2013-10-01 Etex Corporation Porous calcium phosphate bone material

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GB0116191D0 (en) 2001-08-22
GB2377285A (en) 2003-01-08

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