3. Introduction to Hierarchical Process Modelling Dr Mike Yearworth

Reader in Systems Engineering

©  University  of  Bristol  2014  

HPM idea #1 – Hierarchy

•  A  system  can  represented  by  a  network  of  “blobs”  and  “links”  

•  Hierarchy  offers  us  a  way  of  managing  complexity    •  Each  level  the  same  but  expressed  in  more  detail  –  decomposi)on  

•  Decomposi)on  is  the  simple  link  è  Step  1  in  the  modelling  language  we  will  use.  There  is  only  one  kind  of  link  –  a  decomposi)on  

2

HPM idea #2 – Process

•  A  system  can  represented  by  a  network  of  “blobs”  and  “links”  

•  The  “blob”  is  conceived  as  a  transformaJonal  enJty,  a  process  

•  Anything  can  be  a  process  •  Described  by  verbal  nouns  (Also  known  as  gerunds  -­‐  in  English  these  are  words  ending  in  –ing.    

•  They  have  no  subject,  and  the  agent  (performer)  is  not  specified)  è  Step  2  in  the  common  language.  There  is  only  one  form  of  blob    -­‐  a  process  

3

Example of a process hierarchy

4  

Holon

•  Conceptual,  abstract,  representaJon  of  a  whole,  which  is  also  a  part  

•  Used  as  an  conceptual  device  to  think  about  the  world    

•  Conceptual  models  that  consist  of  processes,  described  by  verbal  nouns,  structured  into  a  hierarchical  arrangement  by  decomposiJon  and  represenJng  the  minimum  processes  in  a  system  required  to  achieve  a  purpose  

5

Stimulation of creativity in enactment

•  Even  physical  enJJes  can  be  considered  as  processes:  

“The  chair  is  a  process”  The  chair  is  enacJng  the  process  “suppor)ng  si6er”  

•  Avoids  over  specificaJon  –  I  don’t  need  a  chair,  I  need  something  on  which  to  sit  

•  Enables  the  simultaneous  exploraJon  of  why  and  how  

6

Example – the ‘how’ of “designing” ê

Engineering  Design  

System  Requirements  &  IntegraJon  

High  Level  Engineering  ObjecJve  

Designing  an  intercity  HS  Rail  Link  

Capturing  requirements  (passenger  nos,  travel  

Jme)  

IntegraJng  HS  Trains  &  energy  

infrastructure      

Procuring  COTS  HS  trains  

Building  energy  supply  and  distribuJon  systems  

Defining  preferred  route  and  

staJon  locaJon  

Designing  track,  bridges,    cu\ngs  and  

tunnel  

IntegraJng  signalling,  track  

and  trains  systems  

Designing  signalling  so]ware  

Designing  IT  network  hardware  

7

Thanks to Dr Ges Rosenberg for this example

Rebalancing*

na+onal*economy**

Providing*IT*

connec+vity*

Providing*

interna+onal*air*

transport*

Delivering*an*

intercity*HS*Rail*

Link*

Financing*and*

planning*for*local*

economic*

development**

Sufficient*other*

necessary*

condi+ons*

Delivering*an*

intercity*HS*Rail*

Link*

Gaining*poli+cal*

support*

Achieving*planning*

consent*(legal)*

Designing*an*

intercity*HS*rail*

link*

Consul+ng*on*

proposals*

Demonstra+ng*

value*for*money*

Financing*HS*rail*

system*

Designing*an*

intercity*HS*Rail*

Link*

Capturing*

requirements*

(passenger*nos,*

travel*+me)*

Integra+ng*HS*

Trains*&*energy*

infrastructure***

Procuring*COTS*HS*

trains*

Building*energy*

supply*and*

distribu+on*

systems*

Defining*preferred*

route*and*sta+on*

loca+on*

Designing*track,*

bridges,**cuMngs*

and*tunnel*

Integra+ng*

signalling,*track*

and*trains*systems*

Designing*

signalling*soNware*

Designing*IT*

network*hardware*

Thanks to Dr Ges Rosenberg for this example

The ‘why’ of designing é

8  

Examples… modelling electricity supply risk in the UK

9  

(Marashi  &  Davis,  2007)  

Process of model (holon) building

•  The  top  level  process  enacts  a  transformaJon  •  Challenging  system  boundary  by  asking  why?  •  EliciJng  system  structure  through  repeated  quesJoning  of  how?  

•  Layering  as  required  in  order  to  provide  meaningful  groupings  of  processes  

•  Proceeding  unJl  there  is  no  longer  a  process  answer  to  the  how?  quesJon  (we  are  hi\ng  unresolved  issues)  

10  

Process of model (holon) building

11

Why?  How

?  

Group Model Building: Exercise

•  Create  a  conceptual  model  of  your  system  starJng  from  transformaJonal  top-­‐level  process  descripJon  agreed  in  the  first  exercise.  Use  whiteboards/flipcharts  

•  Remember  to  think  in  terms  of  – purpose,  process,  hierarchy,  decomposiJon,  how  (ê)  /  why  (é)  

•  Present  your  conceptual  model  with  a  view  to  discussing  your  system    

12

References

Blockley,  D.,  &  Godfrey,  P.  S.  (2000).  Doing  it  differently  :  systems  for  rethinking  construc)on.  London:  Thomas  Telford.  

Checkland,  P.  (1981).  Systems  thinking,  systems  prac)ce.  Chichester:  John  Wiley.  Davis,  J.,  MacDonald,  A.,  &  White,  L.  (2010).  Problem-­‐structuring  methods  and  project  

management:  an  example  of  stakeholder  involvement  using  Hierarchical  Process  Modelling  methodology.  Journal  of  the  Opera)onal  Research  Society,  61(6),  893-­‐904.  doi:  10.1057/jors.2010.12  

Koestler,  A.  (1967).  The  Ghost  in  the  machine.  London:  Hutchinson.  Marashi,  E.,  &  Davis,  J.  (2007).  A  Systems-­‐Based  Approach  for  SupporJng  Discourse  in  

Decision  Making.  Computer-­‐Aided  Civil  and  Infrastructure  Engineering,  22,  511-­‐526.    

Simon,  H.  A.  (1991).  Bounded  RaJonality  and  OrganizaJonal  Learning.  Organiza)on  Science,  2(1),  125-­‐134.  doi:  10.2307/2634943  

Sowa,  J.  F.  (1984).  Conceptual  structures  :  informa)on  processing  in  mind  and  machine.  Reading,  Mass.  ;  London:  Addison-­‐Wesley.  

13