STEP data exchange technology and its application in architectural CAD [2009-03-1615: 50] Step technology and its application in architectural CAD; abstract

This paper briefly introduces the STEP technology of data exchange between various softwares and its development at home and abroad.

Keywords: database integration technology building CAD steps

abstract

Summarizes the development and application of STEP (product model data exchange standard) technology, introduces the practice of building thermal design and analysis integrated data model by using STEP technology, and puts forward some suggestions for the development of standard building and HVAC data model.

Keywords: database cibs CAD steps 1 preface

The key to develop an integrated architectural design system is to realize data exchange among CAD tools, analysis software and various databases. To realize an "open" system, all parts of the integrated system can be studied independently.

Brief introduction of two-step technology

Generally speaking, different softwares exchange data through data files. The premise of correct data exchange is to enable the data receiver to "understand" all the received data completely and accurately. Initially, this was achieved through a protocol between a data generator and a data reader. The protocol includes the format, order and quantity of data and the data meaning of each position in the data file.

With the increasing complexity of product and engineering data, the above methods are increasingly unsuitable. The same type of things, different specific objects, have different amounts of data to describe, different physical meanings to express, and even different data types. For example, the structure and quantity of data describing buildings vary greatly with the number of floors, rooms, doors, windows and walls of buildings; To describe the data of an air treatment room, it is meaningful to connect the meanings represented by some data for air treatment rooms with different structures (surface coolers and spray rooms), and a set of data is meaningful only by combining the definition of their relationship. Only by relying on some pre-agreed protocols, it is difficult to accurately reflect the physical meaning of each data and the relationship between the data, and it is even more difficult to adapt to the possible changes in the described things. The physical meaning of data, the relationship between data and the data itself are isomorphic to describe things. Data exchange and transmission should also include these three parts.

Based on the above viewpoint, the step-by-step data exchange technology is proposed. Organize data into data items for storage. Each data item includes several data describing the content of the item, and there may be other data item names related to the content. Each data is stored under its physical name * * *. In order to accurately describe the internal structure of data items and the relationship between data items, EXPRESS should be used to strictly define the internal structure and physical meaning of each data item. The clear definition of this data item is called data model. According to this data model, you can write STEP data files accurately, and you can easily understand the STEP data files generated by this model.

Take describing the geometric dimensions of buildings as an example. Architecture can be regarded as composed of many closed spaces; Every space is surrounded by several loaves; Each surface is defined by several line segments; Each line segment is determined by its starting coordinates. At the same time, each line segment is the intersection boundary of two surfaces; Each envelope has two sides as its sides. This data model can be described in the following expression language:

Entity: building

Includes a set of envelopes.

Include: space set

Final entity:

Entity: space

Consists of the following parts: surface group

Final entity:

Solids: surfaces

Area: true

Consists of the following parts: a group of line segments

Yes: the surface of the envelope

Face: one of them (space, external environment)

Final entity:

Entities: line segments

Point 1: point

The second point: point

Boundary of surface 1: face.

Boundary of surface 2:: face

Final entity:

Entities: points

X is: true.

Y is: true.

Z is: true.

Final entity:

Entity: envelope structure

Edge 1 Yes: a set of faces.

The second surface is: a set of surfaces.

Final entity:

In the EXPRESS data model defined above, capital letters are some keywords determined by grammar. Small English

# 1= building ((#80, #8 1, #82, #85, ...), (#2, each shell structure #3, #60, ...))

The code name of each space

#2= space ((#4, #5, #6, ...))

The code name of each surface

#3= surface (24.5, (# 10, # 1 1, ...), #80, #2))

Each line segment code belongs to the area around the surface.

Envelope space

#4= surface (32, (# 10, # 14, ...), #8 1, #2)

……

……

# 10= line segment (#50, #5 1, #3, #4)

Point 1 point 2 face 1 face 2

# 1 1= line segment (#5 1, #52, #3, #6)

……

#50= point (0.3, 12.8, 0.3)

X, y and z coordinates.

#5 1= point ( .........................................................

……

#80= envelope (#3, #4)

In the above STEP file, #n is only used as the identification name of a piece of data, and its order is meaningless. The name after the equal sign gives the structure of the data. Indicates that the contents in parentheses must be consistent with the structure defined by the entity in EXPRESS. #n in parentheses indicates the correlation between data.

In this way, the data file has nothing to do with the data order, and the total number of items can be very different according to the complexity of the described things. As long as its data model is obtained, all data content can be generated or understood. In this way, the data model defined by EXPRESS is equivalent to a strictly defined data file protocol. On the basis of its openness and consistency, the accurate understanding of data can be realized.

Of course, the information involved in the actual construction is far more complicated than the previous example, but it is the same.

The foundation described in the above example is based on the consistency of the data model. If the data model is inconsistent, that is, the perspective of looking at and describing things is inconsistent, this data exchange cannot be realized. For example, if a software uses the centerline of each wall to describe the geometric information of a building, it is difficult to directly express its data with the above data model. Therefore, it is the key to develop a unified standard data model, that is, a unified definition file in the form of EXPRESS, and to use and popularize STEP technology for data exchange.

After more than ten years' efforts, many software tools using STEP have been developed. For example, NIAM；; Define the data model graphically and generate the EXPRESS file directly; Automatically convert EXPRESS files into data type descriptions in CCGENC++; Dynamic database software, which directly stores and retrieves data in step-by-step form. At present, a preliminary attempt is made in three steps.

And British architectural studies

Using this system, the user first describes the three-dimensional geometric shape of the analyzed building on AutoCAD, and defines the physical properties of each building component by selecting the corresponding components from the door, window and wall component library. These input results are converted into data items of STEP and stored in the database. Users can call the calculation software to analyze the building. For example, check whether the envelope meets the thermal insulation standard or estimate the energy consumption. Users can further define the required room range and HVAC form, so as to calculate the load or natural room temperature. These calculation results are also stored in the database and can be used by other software. Because of the open structure, the system can also run ready-made calculation and analysis software. at present

The system is still in the process of development, but it has shown the superiority of STEP mode. With the increase of system complexity, this advantage will become more and more obvious.

4 Suggestions and ideas

With the development of computer technology

The core of using STEP technology is to develop and establish a data model. Making a standard EXPRESS building data model and making everyone follow it STEP by step is the key to make STEP technology benefit in the field of building CAD. At present, it is impossible for STEP standardization organization to directly engage in this work, and it can only rely on the cooperation of domestic units engaged in the development and research of architectural CAD and analysis simulation software. This work will be done sooner or later, and the sooner it is completed, the sooner it will be effective, and the repeated development and application will be eliminated as soon as possible. /A & gt； Waste software.