1.3 Classifying Engineering Tasks Knowledge Component 1: Theoretical Foundations Computer-Aided Engineering 1.3 Classifying Engineering Tasks 2nd Edition Ian F. C. Smith EPFL, Switzerland

Module Information Intended audience Key words Author All Engineering tasks Inference Well-defined tasks Author Ian Smith, EPFL, Switzerland

What there is to learn At the end of this module, there will be answers to the following questions (see also the review quizzes): What is the point of studying the links between logic and engineering tasks? Should a computer provide single answers or choices? What is the logical similarity between design and diagnosis?

Outline Engineering Tasks Inference Model of Information and Tasks Well-defined and Poorly-defined tasks (Newell 1960)

Definitions Structure (or Form) Information represented in drawings (dimensions, location, topography, etc.) as well as properties of materials and environmental context. The scope of this definition is not limited to structural engineering! Behavior Includes parameters that describe how the structure reacts (deformations, stresses, buckling, creep, etc.) Cause External actions resulting in a change of behavior Effect Observed behavior under the influence of the cause

Engineering Tasks - Examples Analysis Structure Behavior Simulation Cause + Structure Effect Diagnosis Effect + Structure Cause Synthesis Required behavior Structure = inference 6

Engineering Tasks (cont’d.) Experimental Research or Interpretation of Information Structure + Behavior models Behavior Observe that synthesis is reverse analysis and diagnosis is reverse simulation

Outline Engineering Tasks Inference Model of Information and Tasks Well-defined and Poorly-defined tasks

Inference Inference is the reasoning involved in drawing a conclusion or making a logical judgment on the basis of evidence. Rule: If cause then effect Given cause, effect and rule, there are three types of inference Deduction Abduction Induction

Types of Inference Type of Inference Given information Inferred information Deduction Cause and rule Effect Abduction Effect and rule Cause Induction Cause and effect Rule

Review Quiz I What types of inference are more likely to have multiple answers? What types of inference are more sensitive to missing information? What types of inference can be associated with the five engineering tasks discussed earlier?

Answers to Review Quiz I What types of inference are more likely to have multiple answers? Abduction and induction. Their use is reliable only if it assumed that all possible rules are known What types of inference are most sensitive to missing information? Abduction and induction, since additional information may change answers What types of inference can be associated with the five engineering tasks discussed earlier? Analysis and simulation are deduction Synthesis and diagnosis are abduction Experimental research and interpretation of data are induction

Model of Information and Tasks Outline Engineering Tasks Inference Model of Information and Tasks Well-defined and Poorly-defined tasks

Types of Information Three Categories Structure (S) (dimensions, shapes, properties of materials, loads, temperature, etc.) Behavior (B) (deformations, shrinkage, creep, stress, displacements, corrosion, etc.) Function (F) (design criteria, specifications, desires of society, purpose, etc.)

Types of Information (cont’d.) It is important to organize project information appropriately. Good organization helps make modifications and additions without introducing update errors. Modifications and additions always occur in large engineering projects.

Tasks and Types F = Function transformation B = Behavior S = Structure Sas-designed Brequired synthesis formulation (standards) F = Function B = Behavior S = Structure transformation

Tasks and Types (cont’d.) F Sas-designed Bpredicted Brequired analysis traditional evaluation synthesis formulation (standards) F = Function B = Behavior S = Structure transformation comparison

Tasks and Types (cont’d.) F Sas-designed Bpredicted Brequired analysis traditional evaluation synthesis Sas-built construction formulation (standards) F = Function B = Behavior S = Structure transformation comparison

Tasks and Types (cont’d.) monitoring F Sas-designed Bpredicted Bmeasured Brequired analysis traditional evaluation synthesis Sas-built construction formulation (standards) prediction improvement of models diagnosis F = Function B = Behavior S = Structure transformation comparison

Tasks and Types (cont’d.) The diagram in the previous slide is a representation of transformations. The iterative aspect is not shown. For example, if the traditional evaluation task fails, modifications to either F, Brequired or Sas-designed are carried out until traditional evaluation succeeds. Analysis refers only to calculation. Improvements in analysis may also help the traditional evaluation task. Creation of numerical models is a synthesis task (creation of a model of Sas-designed).

Tasks and Types (cont’d.) Some tasks are used to complement information. For example, synthesis is used to add information concerning the structure. It starts with assumptions about the environment in which the structure will be found. Some tasks, such as synthesis and diagnosis, may have more than one possible solution.

Review Quiz II What inference occurs at each task in the FBS schema ?

Answers to Review Quiz II What inference occurs at each task in the FBS schema ? deduction and abduction F Sas-designed Sas-built deduction abduction abduction deduction deduction abduction Bpredicted Bmeasured Brequired deduction induction

Well-defined and Poorly-defined tasks Outline Engineering Tasks Inference Model of Information and Tasks Well-defined and Poorly-defined tasks (Newell 1960)

Well-defined Tasks Carried out in closed worlds (all information is known) and Defined by goals explicitly expressed non-ambiguously by an objective function (for example, using a mathematical formula) Described by algorithms that lead to identification and numerical quantification of a solution

Poorly-defined Tasks Open world conditions prevail (not all information is known) or Goals are defined only partially Definitions of solutions are incomplete Procedures for obtaining solutions are not known completely Engineers are entrusted by society to perform poorly defined tasks. These tasks usually add the most value to society.

Questions What is the point of studying the links between logic and engineering tasks? Software requirements are similar for tasks that are associated with similar types of inference. Should a computer provide single answers or choices? It depends. Single answers are usually enough for deductive tasks whereas abductive tasks often require choices amongst many possibilities. What is the logical similarity between design and diagnosis? These tasks are both abductive. Therefore they require similar types of computer support.

Further Reading Gero, J. S., 1990. Design Prototypes: A Knowledge Representation Schema for Design. AI Magazine, 11, 4 pp 26–48 Raphael, B. and Smith, I.F.C. Fundamentals of Computer-Aided Engineering, Wiley, 2003