The
Shared Project Model
The shared project model is the second approach to project data integration.
It would replace individual paper or electronic documents with a single knowledge
base describing an entire project. Participants would have real-time access
to the model throughout the life of the project, in turns contributing their
own knowledge and using information contributed by others. Each discipline
that a project team comprises, from surveying to finance, would continue
to use specialized tools for performing its own aspect of the work, but these
tools would have the ability to draw from and contribute to, a common pool
of information. For example, a mechanical engineer would continue to work
with tools specific to his discipline but within the context of an intelligent
information system that does not require reentry or translation of information
once it has been created.
The key change from present practice is that all specialist tools can transparently
exchange information with the shared project model. Elements of a building
would be represented as objects, containing physical attributes as well as
graphical and textual information about the item. This is very different
from CAD as it is used today, which automates hand drafting but does not
endow what it draws with more than geometric information. Objects within
a building model carry with them dimensional data, as CAD objects do, but
also richer information, such as specifications, code and performance data,
cost, and information related to construction means, methods, and schedule.
For example, an object representing a steel beam would be drawn, first, architecturally,
with its physical characteristics; second, structurally, with its load-bearing
properties; third, as a cost item; fourth, as a scheduled process of fabrication
and delivery, and so on. Each participant would draw on the common object
to access the information and manipulate it with discipline-specific software.
An architect would draw and model, an engineer would calculate, and a construction
manager would schedule, all using information from a common project database
that is accessible over a network. Instead of creating standalone CAD drawings
and models, architects would contribute the physical design attributes of
a building to the larger computer representation of the building as both
an object and a process. Now, CAD drawings become just a kind of report,
reflecting only one aspect of the total process represented in the model.
The shared project model becomes almost a living organism that can be accessed
asynchronously by its many contributors. Information is now available in
context-specific forms, rather than inflexible paper-based presentation formats.
Teams could have multiple “live versions” of a project available
simultaneously to support design collaboration.
Object-oriented
and Parametric 3D Modeling
So-called object-oriented CAD derives from object-based programming in the
software industry, which discovered that complex applications could be quickly
and easily assembled from a kit of preexisting parts. Blocks of code are
assembled into larger components. Java and C++ are examples of object-oriented
programming languages.
Object-oriented CAD is a new standard for modeling physical objects
such as building components. At first, CAD was used to automate
hand drafting,
the creation of 2D drawings such as plans, sections and elevations. Such
drawings consisted of lines and shapes without any intelligence about what
the lines and shapes represented. A CAD program can draw a window with a
fine degree of geometric precision, but it does not know about the window’s
energy efficiency or what it costs or how long it takes to install. The idea
behind object-oriented CAD is that rich information about building components
could be modeled in a form accessible by a wide variety of software applications
and used throughout a building’s life cycle without conversion or translation
into other formats. Properties including shape, behavior, performance data,
and transport requirements, along with embedded links to relevant code requirements
and test results, could all be included in an electronic “object.” When
an architect adds a door, the door object will describe not only the physical
attributes of the door needed for design by the CAD program, but also the
cost, maintenance, supply and installation properties of the door for use
in project costing and scheduling, and later for facilities management.
Parametric modelling was originally developed for aerospace and process-plant
engineering. The three-dimensional computer modelling process works like
a row-and-colmn spreadsheet. By storing relationships between the various
features of the design and treating these relationships like mathematical
equations, any element of the model to be changed automatically regenerates
the model in the same way that a spreadsheet automatically recalculates a
change in numerical value. As can be seen in the work of Frank Gehry, it
allows complex shapes to fabricated directly from the design model.
Models
and Metaphors
The computer industry likes to use metaphors to describe concepts.
Sometimes the metaphorical use becomes so widespread that it
supersedes the original
term. Many architects have noticed how many terms have been borrowed from “our” vocabulary—site,
user, program, and of course, the term architecture itself. Sometimes the
result is confusion between metaphors and the real-world concepts to which
we think they refer. For example, when an architect or builder imagines object-oriented
CAD, she probably thinks about real, physical things such as doors or bricks.
Actually, “object-oriented” derives from a programming concept
in which blocks of code can be assembled into larger components. Java and
C++ are examples of object-oriented programming languages.
Model is a term that has come to be used in many contexts.
A physical model, such as those architects make out of wood and cardboard,
is easy to understand but limited in its use. It must be physically
transported from place to place. But it is a powerful representational
tool because it is intuitively grasped and highly interactive.
A computer model is another kind of model. It lacks the toylike charm
of a physical model but compensates with versatility, ease of revision,
and
portability.You can alter the time of day and the season, create walk-throughs
and fly-overs, and export views of the model for rendering, video, and immersive
imaging techniques such as QuickTime VR. But a geometric three-dimensional
model is only one kind of computer model. It contains only a subset of the
qualities of the objects being modeled. Models may include shapes, lines
and points, or three-dimensional components such as blocks, cones and spheres.
Other kinds of computer models include parametric, procedural, and generative
models. Parametric models permit the relationship between elements to be
seen.When a variable is changed, its effect is seen on related elements.
Procedural models add the ability to set parameters for such relationships,
ensuring, for example, that incompatible elements cannot be placed adjacent
to each other, or that a door is not swinging in an illegal direction. Generative
models create geometries that fulfill requirements entered by the user, such
as:“generate the optimal layout of theater seats for this auditorium” or “create
a single-run stair between Floors 1 and 2.” Generative models follow
rules set by the designer, such as “seat rows shall be 22 inches apart” or “risers
shall not exceed 7 inches.”
The shared project model as a new paradigm for describing buildings refers
to models that embody three-dimensional geometric information, but also information
about the attributes of the object being modeled, such as what it is made
of, who makes it, what it costs, how long it lasts, or how many worker hours
are needed to install it.The shared project model is not necessarily a literal
model at all, but a kind of database. It is sometimes referred to as 4- or
even 5-D CAD, where the three physical dimensions are augmented by time and
cost.
return to part one
learn about the Building Connections conference held on April 30, 2004 in Washington
