BOTTELLI - PAOLO DRAGO - CHRISTIAN FOGH
developed from a proposal of Prof. EZIO ARLATI
Ph.D. Research in Technical Innovation and Architectural Design
di Progettazione, Programmazione e Produzione Edilizia
Facoltà di Architettura Politecnico di Milano
Via Bonardi, 3
20133 Milano - Italia
tel. (-39-2) 2399 - 5125
paper discusses some problems and positions regarding process control
in architecture and some possible solutions offered by knowledge-based
systems, in particular with the aid of case-based reasoning techniques.
The requirements of an integrated computer-based environment for the
control of quality design process are then surveyed as a list of guidelines
for future research work.The paper presents some theoretical landmarks
identified during the first year of Ph.D. research and an experimental
hypothesis aimed at verifying the main assumptions made. A first experimental
hypothesis based on the creation of a CBR tool centered on the management
of precondiotions as cases is presented. Conclusions include some
on-going work showing possible directions for future experimental
The experimental work concentrates on the functions of integration,
case-based reasoning, information transformation and design process
case-based reasoning; computer-aided architectural design; design
process control, knowledge-based design; memory-based design
design has been the object of formalization efforts for several decades,
and most authors now converge on its definition as an intentional
human activity, characterized by the search of a path leading from
a starting state to a goal state. (Colajanni et al. 1991)
Initial CAAD research studies focused on a procedural mechanistic
model of the process, based on 'stepwise refinement' (Dahl et al,
1972), i.e.in which each phase could be subdivided into sub-phases,
each independent and consequent to the preceding ones, so that each
phase could be tackled separately. This presupposed design activity
as a well-defined problem, amenable to algorthmic treatment.
More recent work, also thanks to the use of AI, has emphasized the
growing importance of the knowledge base, shifting towards a heuristic
conception of design, which de facto becomes a path between increasingly
accomplished model thresholds as the involved variables reach a more
formalized degree of solution.
For example, the proposal of a prototype refinement paradigm (Gero,
1987, Oxman and Gero, 1988, Gero and Rosenmann, 1990), describes design
as based upon a knowledge base in which past experience is condensed
in abstract, context independent prototypes, which are progressively
refined and contextualized by means of design procedures.
Other authors, such as Smithers, go so far as to refuse an a priori
decomposition of the process into sub-phases, considering it a global
activity occurring in a contemporary and non-linear evolution of the
requirements and design state through continuous reciprocal adaptation.
(Smithers et al, 1990, 1991)
What emerges from these and other theoretical approaches is a profoundly
modified vision of the design process and of the role the designer
holds within the process, probably also due to the growingly complex
and ill-defined nature of the design activity as new variables and
new contexts keep arising.
Thus, in a context of "turbulent complexity" (Maldonado,
1992), the decision process at the basis of the design activity should
abandon all sectorial approaches and be founded upon a design method
receiving all variables and items present from the very first heuristic
phases of the project, so as to reach a first preliminary solution
In such a context, an increasingly central role belongs to those aspects
referring to the knowledge-base of design, and in particular to those
aspects pertaining to memory. In fact, the importance of the knowledge
and memory base in relation to intelligence is now a wholly accepted
concept in AI and cognitive psychology. (Kolodner, 1991). A well organized
knowledge and memory base is essential for an effective interaction
with the environment; the effectiveness grealy depends upon the methods
of indexing and retrieval, which are certainly subjective and dynamic.
Some authors thus introduce a subtle distinguo between knowledge-based
and memory-based processes, considering the latter more adquate to
describe the design activity since its main resource is a memory container
in continuous growth, modification and adaptation. (De Grassi et al,
In fact, when takling a new design problem, it is known that we strongly
base our search path upon previous experience: we browse in our memory
of precedents for a relevant example (or case), recall the solution
process, and thus adapt the previous solution procedure to the new
Case-based reasoning is a reasoning paradigm based upon the modelling
of memory and experience. It is characterized as a problem-solving
approach inferencing from previous solutions which are adapted to
current situations. It has proved useful in domains where experience
is strong but domain model is weak (Oxman, 1994), which is generally
true of design contexts. CBR is constructed on the basis of cognitive
models for knowledge formulation and memory organization and it is
enacted with a variety of operational tools apt to represent, index,
retrieve and modify objects (or cases).
A rich area of cognitive science research has concentrated upon the
modelling of memory and the development of representation tools, investigating
the types of memory processes involved in design (semantic, episode,
conceptual etc.) and the possible representation schemes apt to describe
them (scripts, frames comprising objects, slots and methods). The
cognitive content of this research area has posed a number of assumptions
regarding memory which have been as the cognitive bases of CBR; the
implementation of these concepts is clear and rich of possibilities
for the CAAD field of research. Cases may be represented by means
of schemes such as rules, scripts and frames and a frame language
may be seen, amongst other things, as a precursor of object-oriented
languages, with all the consequent modularity and efficiency characteristics
typical of this technique.
Regarding process modelling, some authors propose flow diagrams illustrating
typical reasoning and learning schemes based on cases. Such diagrams
are mostly constructed with the following iterative steps: indexing,
retrieval, adaptation, test, new indexing and memorization or explanation
for failure, correction and testing.
The present research has deliberately not entered into memory process
modelling, since at the present state none of these functions will
be automated and the emphasis is on the central role of the designer
in the process.
In fact, after a first generation of KBS studies utillizing CBR concentrated
research efforts into trying to replicate human knowledge, current
work is primarily directed at a partnership between the human and
machine agent. (Oxman, 1994). Thus, the objectives of such systems
are to "enhance human decision making by suggesting alternatives,
predicting consequences and pulling together the information that
goes into decision making" (Winograd and Flores, 1986). One such
case-based system developed in Italy, which has greatly influenced
our work, is centered upon a case engine interacting with a rule basse
and a case memory and wholly respects the paradigm of designer centrality.
(De Grassi et al, 1992).
In this view, CBR is directed at assisting conceptual design with
a readily accessible acquisition and retrieval of past experience
relevant to the present context. How can this be done?
Both from a cognitive and technological point of view, CBR supplies
a reasoning paradigm which may be applied to most subjective, non-procedural
and hardly formalizable aspects of design. In fact, when designers
derive ideas and temporary solution schemes from past experience,
they do so on the basis of different cognitive mechanisms (analogy,
etc.) which are arbitrary, subjective and hardly logical. Thus, a
case-memory may be described as a case-container in which all connections
and their semantics are managed by designers themselves, according
to their beliefs and personal standards. The organization of memory
is therefore an expression of a designer's mentality.
Moreover, CBR does not presuppose any a priori methodological approach,
that is, it allows for bottom-up, top-down or even middle-out strategies.
It may be useful both in underconstrained and overconstrained problems.
A case is the basic unit in a CBR system and in literature it is generally
consistuted by a design solution, however well-defined. In this paper,
an experimental prototype is described, in which a different perspective
is utilized and the set of pre-conditions imposed on projects by a
designer is used as a memory-base. The general assumption is that,
by means of the kind of pre-conditions imposed on projects in different
design contexts and phases, a designer builds up a personal memory
base highly tailored to specific experience and habits.
The present paper presents early work started in the faculty of Architecture
of Milan, pertaining to the first one and a half year of Ph.D. research
of three students.
The main goal of the research as a whole is the analysis of the quanta
of information required along the design process and the consequent
description and representation of the It is in fact necessary to proceed
along the phases of the process incorporating from the very beginning
all those variables and issues involved, thus considering each step
of the process as temporary solution for the specification level reached;
in other words as a virtual model of transformed reality representing
those parts of the project which have already been explored, and passible
of modifications in its configuration, so as to incorporate changes
brought by new levels of specification.
Stemming from this general goal, the on-going research work has first
of all been devoted to the analysis of the requirements of an integrated
environment for the support of quality design incorporating the issues
raised. Below are listed some specifications considered an essential
background for future experimental work:
open - the environment should be able to continually accept new contributions
and operative grounds as well as guarantee storage and reuse of data
in the original format and compatibility of formats
adaptable to user's way of working - this means the possibility to
incorporate information, functions and programmes required by a designer
in a given moment and offer them in the necessary format. This should
also be modifiable in time.
integrated - the environment should consist not in one programme but
in a system allowing. Such programmes should be operate in full intercommunication,
by means of technological tools and should possess a common user interface.
flexible and potentially "omniprogressive" - the system
should be extendable and potentially "omniprogressive" (i.e.
capable of incapsulating useful functions as new needs emerge, thus
following projects along their growth in complexity). In other words,
this means envisaging a highly flexible structure, within which it
should be possible to choose infinite subsets according to needs.
In this way, the environment is capable of describing and accompanying
the design process and to endow itself dynamically with programmes
and functions as one or more variables emerge or vary. This means
that the system connects with new and different programmes during
a project's life span, enacting a truly heuristic approach to design.
This should guarantee a high degree of flexibility to the system,
eliminating defects and inconveniences deriving from centrally organized,
costly and rigid models.
centrality of designer - in no case should the system have the aim
of emulating or taking the place of designers, but of aiding and supporting
them in those functions in which they most need help. Interaction
should best be passive (I warn you that... - open possibilities are...
etc.) rather than automatic. If automatic interaction is included,
it should always be possible to disactivate it, so as to return the
central role to the designer's will.
user friendly interface - the central nucleus which allows free migration
between programmes, and communication between designers and system
should be as intuitive and user friendly as possible. This both regarding
representation and management, considering that designers are generally
more familiar with visual rather than verbal messages.
One main issue in the integration of specific tools for the support
of design process is the resolution of conflicts. One paradigm which
has always guided this research is the central role of the designer
in process control - thus, resolution of conflicts will be wholly
left in the hands of designers' judgement.
As regards the tools to be integrated in a design environment, modules
are needed covering the areas of drafting, simulation, communication,
project management, data-bank connection as well as others, allintegrated
into a framework allowing free migration amongst programmes.
a first experimental step in the pursuit of the above described aims,
a first prototype, devoted to the functions of verification of pre-conditions
and case-based reasoning is presented.
The object of this prototype is that of implementing, even if on a
small scale and compatibly with the instruments available in the Computer
Technology Laboratory of our Department, the central issues of our
research, which may be summarized as follows:
central role of designer in the building process
control of increasingly complex information quanta
continuous updating of qualitative information
constitution of a personalized file of cases
verification of pre-conditions imposed by the designer on the basis
of the specific needs of a given project or project phase. Such pre.-conditions
may be interchangeable and of different sorts: from technological
to legal, cultural etc. so as to guarantee the paradigm of flexibility
The structure of the prototype therefore consists of an environment
incorporating the following elements:
an object-oriented, parametric CAAD tool (Archicad for Windows)
a rule-based system for the analysis and verification of pre-conditions
a filter (in C language) connecting objects present in the CAAD and
in the rule-based system.
A) MANAGEMENT OF PRE-CONDITIONS
implementation of this function of the prototype may be sub-divided
into four different phases:
Interface with a specific CAAD system
During this first phase, the system, reading the CAAD database, recreates
intrinsically the taxonomic structure of all objects costituing a
project, analyzing and recovering all object slots (parameters), i.e.
transfers all technical and spatial information present in a project.
This first phase may be implemented both manually (i.e. the final
user inputs data from the programme structure - this is essential
if not using an object oriented CAAD), or automatically. In this latter
hypothesis, which is present in this prototype, the system itself
directly translates information present in the CAAD objects into CLIPS
facts, on which rules may operate. This interface module is written
in C language and needs to be adapted if other CAAD systems are used,
since there is yet no standard amongst CAAD databases.
Editing of pre-condictions
the basis of parameters memorized from CAAD and translated into facts
in the CLIPS database, the user may input certain preconditions into
the system, that is, to insert rules, which, at the moment are to
be formulated in CLIPS language, but later in natural language.
These pre-conditions satisfy the following characteristics:
may be activated, disactivated, changed or erased at any time
may be expressed by means of CLIPS syntax; in future they should be
expressed in a sub-language of natural language, or, ideally in natural
In case pre-conditions are incompatible, the system activates a truth-maintenance
system (TMS) operating on facts and rules, which alerts users requesting
a conflict resolution before running verification of pre-conditions.
Verification of pre-conditions
any step in the design process, users may ask the system for the control
of previously input preconditions. The system will thus respond through
screen messages informing on preconditions violated, as well as informing
on whether rules have been satisfied and supplies a succinct explanation
of its reasoning path up to the moment of arrest. Rule verification
may also be operated on-line, that is, after any project modification.
The verification of preconditions may activated globally on the project
or on subsystems or even only on single classes of assembled objects.
4)Storage of dinstinct project phases
any given moment, users have the possibility to store facts and rules,
thus creating a planning data-base which may prove extremely useful
during the development of other projects.
In particular, starting from a given project, the system may list
all pre-conditions pertaining to it, and/or viceversa, starting from
a given set of pre-conditions, the system may propose all stored projects
or parts of projects satisfying those pre-conditions. Using such a
project case memory, the system may also automatically propose all
given sets of rules satisfied by a specific project.
Indications for future research
research work, starting from the results acquired from this first
prototype, is concentrating on further theoretical and experimental
One on-going experiment is aimed at incorporating in the previous
prototype external "poor" information, translating it into
quality information supplied to designers exactly when needed and
in the degree of definition needed according to design phases.
The operative hypothesis is that of constituting an integrated knowledge-based
environment which, according to the growing needs of the project,
is able to endow designers with qualitative and suitable information.
This is enacted by means of the connection with available, "poor"
information sources, which, when needed, extract and transform information
into quality data, and subsequently integrate it into the growing
Such information sources may be of several kinds: technological, legal,
geographical, cultural etc. - i.e. all those multiform areas of knowledge
utilized by designers for reference iduring the planning control process.
One hypothesis, currently under realization, is that of integrating
existing "poor" information sources such as various types
of CD-ROMs (technological, legal, geographical, cultural etc.) into
nvironment created with the first prototype, i.e. using Archicad for
Windows and CLIPS. CD ROMs are readily available, rapidly evolving
and presently of poor quality. The data present in these sources will
be translated by a filter module in C language into objects/facts
capable of interacting with the precondition verification module and
with the case memory.
AND TRANSLATION OF EXTERNAL DATA-BANK INFORMATION
implementation of this additional module of the prototype may be sub-divided
into two different phases:
Interface with specific data-base source
this first phase, the system creates a bi-unique correspondance between
parameters of objects present in the CAAD intrinsic data-base and
the parameters of the items present in the external data-base. This
may be activated manually by the user or automatically.
For a given object, the system thus suggests both sets of parameters
- in this way the user may associate the same information described
in two different ways.
This first phase has the aim of enacting a filter module apt to interpret
information present in the external data-base (e.g. CD-ROMs etc.),
transforming "poor" information into quality information.
of CAAD data-base and creation of Case-library
Once phase 1 has been implemented and the system is thus able to decode
information present in external data-bases, the user may in any moment
use this data to update the current CAAD data-base and the case-library.
The calculation module has the function of updating all parameters
present within the project data-base and/or of introducing new objects
within it. The aim of this function is that of enriching and personalizing
the CAAD data-base, according to the specific needs of a project,
one of its parts or according to the preferences of the designer.
This system may be planned so as to work, with limited modifications,
in association with any CAAD system and any sort of external data-base
Further areas of research include theoretical investigation, in cooperation
with the department of psychology, into which steps of the design
process to assist with AI functions. Research work in this direction
includes hypotheses on distributed models, in particular regarding
the position of elements included into an inegrated system as agents,
and the possible envisaging of the designer himself as an agent, or
Another field of research pursues the analysis on the integration
of technical information, trying to achieve a full integration of
"poor" information sources and their transformation into
quality information sources, capable of ielding the adequate amount
of information according to the design step.
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