how can i add some new entify or property to module ifcopenshell?

[Zhijian Jin]

I try to add some new entify and some Propertifies to do my research about Building heating control . I try to use methode ifcopenshell_wrapper.new_IfcBaseClass, but i need a schema_identifier. What is this Schema_identifier?

[Thomas Krijnen]

It's not very clear whether you want to add:
an entity to the schema, or
an instance of an existing entity to an IFC file

For the first. I would recommend to create an Express file. Just use an existing one as a starting point and add the schema.

Then you can use the dynamic latebound schema parser. Only available in Python and do something like this:

import ifcopenshell
import ifcopenshell.express
schema = ifcopenshell.express.parse('my_new_schema.exp')
ifcopenshell.register_schema(schema)
f = ifcopenshell.file(schema=schema.schema_name)

If it's just about the 2nd option, you open a file with

f = ifcopenshell.open() or start a new file with ifcopenshell.file(schema=...) and use convenience methods such as f.createIfcWall(GlobalId=ifcopenshell.guid.new(), ...)

[Zhijian Jin]

Hello Thomas,
thank u for ur informative answer! I am trying to creat some new ifctype, for example "ifctoken" to say if a pump on or off.
what do u mean add schema to the Express file? What does schema looks like and how can i add it?

[Thomas Krijnen]

I meant an express file like this http://standards.buildingsmart.org/IFC/RELEASE/IFC4_1/FINAL/EXPRESS/IFC4x1.exp

Here are the entities defined. You can parse this using ifcopenshell.express.parse() and create a model using it.

[Zhijian Jin]

Thank u! That's what I am looking for all the time! I can move on to next step now.

[Zhijian Jin]

Hello Thomas,

i copy the express file in txt and change the name to somethin.exp, but i can only get a empty express_parse in file ordner express. What I did wrong?

[Thomas Krijnen]

express_parse in file ordner express

what do you mean by this?

Can you share exactly what you have tried?

[Zhijian Jin]

Thank for ur Answer. That's my bad i didn't describe it clearly.

I copyed the express file that u show into a txt file and tried to bild a new type ifctoken in it by copy ifcwall. I copyed and changed all text, that have ifcwall in it, to text for ifctoken.

And i build a py.file in the same path address:

import ifcopenshell
import ifcopenshell.express
schema = ifcopenshell.express.parse('my_version.exp')
ifcopenshell.register_schema(schema)
f = ifcopenshell.file(schema=schema.schema_name)

after run i have Error message:

 File "somewhere\mycode.py", line 9, in <module>
    schema = ifcopenshell.express.parse('my_version.exp')

  File "D:\Annaconda\lib\site-packages\ifcopenshell\express\__init__.py", line 19, in parse
    mapping = express_parser.parse(fn)

AttributeError: module 'express_parser' has no attribute 'parse'


Traceback (most recent call last):
  File "D:\Annaconda\lib\site-packages\pyparsing\core.py", line 1854, in parse_file
    file_contents = file_or_filename.read()
AttributeError: 'str' object has no attribute 'read'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "bootstrap.py", line 102, in <module>
    express = grammar.parseFile(os.path.join(os.path.dirname(__file__), 'express.bnf'))
  File "D:\Annaconda\lib\site-packages\pyparsing\core.py", line 1856, in parse_file
    with open(file_or_filename, "r", encoding=encoding) as f:
FileNotFoundError: [Errno 2] No such file or directory: 'express.bnf'

And I find when i go into ifcopenshell module file, go into a file folder "express file". A empty .py file named "express_parser" is made. See the picture that I uploaded.

That is my situation right now.

[Thomas Krijnen]

You probably have an older version. That file has been added to repo on Dec 2020 https://github.com/IfcOpenShell/IfcOpenShell/commits/v0.7.0/src/ifcopenshell-python/ifcopenshell/express/express_parser.py previously it was being generated on the fly

[Zhijian Jin]

Hi, Thomas,

here is my main code, I use txt to save express file:

import ifcopenshell
import ifcopenshell.express
import os
schema = ifcopenshell.express.parse('my_version.txt')
ifcopenshell.register_schema(schema)
f = ifcopenshell.file(schema=schema.schema_name)

it goes to express_parser
here is the code express_parser:

import os
import sys
import pickle

import schema
import mapping

from pyparsing import *
from nodes import *

def parse(fn):
    cache_file = fn + ".cache.dat"
    if os.path.exists(cache_file) and os.path.getmtime(cache_file) >= os.path.getmtime(fn):
        with open(cache_file, "rb") as f:
            m = pickle.load(f)

what means ".cache.dat" here? It makes the code can't find my express file.
But if i delet ".cache.dat", I get Error message in line m = pickle.load(f): _pickle.UnpicklingError: invalid load key, '\x0d'.

[Thomas Krijnen]

express parsing is a bit slow, so the resulting syntax tree is cached.

os.path.exists() won't throw an exception it's just a check if the cache exists.

you probably have 'my_version.txt' in another directory than the current working directory where you are running the script. Maybe use an absolute path for 'my_version.txt'

[Zhijian Jin]

Thanks Thomas, i thought that was a Error, but it was just a check.

I run my main code above and i got a Error message:

File "D:\DOC\BA\IFCfile\ifcmodulechange\nachantwort.py", line 10, in <module>
    schema = ifcopenshell.express.parse('my_version.txt')

  File "D:\Annaconda\lib\site-packages\ifcopenshell\express\__init__.py", line 19, in parse
    mapping = express_parser.parse(fn)

  File "D:\Annaconda\lib\site-packages\ifcopenshell\express\express_parser.py", line 480, in parse
    ast = syntax.parseFile(fn)

  File "D:\Annaconda\lib\site-packages\pyparsing\core.py", line 1865, in parse_file
    raise exc.with_traceback(None)

ParseException: Expected CaselessKeyword 'schema'

here is the code for pyparsing/core.py, where raise exc.with_traceback(None) runs:

def parse_file(
        self,
        file_or_filename: Union[str, Path, TextIO],
        encoding: str = "utf-8",
        parse_all: bool = False,
        *,
        parseAll: bool = False,
    ) -> ParseResults:
        """
        Execute the parse expression on the given file or filename.
        If a filename is specified (instead of a file object),
        the entire file is opened, read, and closed before parsing.
        """
        parseAll = parseAll or parse_all
        try:
            file_contents = file_or_filename.read()
        except AttributeError:
            with open(file_or_filename, "r", encoding=encoding) as f:
                file_contents = f.read()
        try:
            return self.parse_string(file_contents, parseAll)
        except ParseBaseException as exc:
            if ParserElement.verbose_stacktrace:
                raise
            else:
                # catch and re-raise exception from here, clears out pyparsing internal stack trace
                raise exc.with_traceback(None)

I totally don't understand what is going on here. Pls help.

[Thomas Krijnen]

It failed to parse your file my_version.txt what's in it?

[Zhijian Jin]

It's original express file plus my new entify 'ifctoken'
I just search all text with word "ifcwall" and creat new text no more with "ifcwall" but with "ifctoken"
Here is what i added to the express file.

TYPE IfcTokenTypeEnum=ENUMERATION OF
    (TOKEN
    ,USERDEFINED
    ,NOTDEFINED);
END_TYPE;

ENTITY IfcBuildingElement
 ABSTRACT SUPERTYPE OF (ONEOF
    (IfcBeam
    ,IfcBuildingElementProxy
    ,IfcChimney
    ,IfcColumn
    ,IfcCovering
    ,IfcCurtainWall
    ,IfcDoor
    ,IfcFooting
    ,IfcMember
    ,IfcPile
    ,IfcPlate
    ,IfcRailing
    ,IfcRamp
    ,IfcRampFlight
    ,IfcRoof
    ,IfcShadingDevice
    ,IfcSlab
    ,IfcStair
    ,IfcStairFlight
    ,IfcWall
    ,IfcWindow
    ,IfcToken))
 SUBTYPE OF (IfcElement);
 WHERE
    MaxOneMaterialAssociation  SIZEOF (QUERY(temp  SELFIfcObjectDefinition.HasAssociations 
  'IFC4X1.IFCRELASSOCIATESMATERIAL' IN TYPEOF(temp)
  )) = 1;
END_ENTITY;

ENTITY IfcBuildingElementType
 ABSTRACT SUPERTYPE OF (ONEOF
    (IfcBeamType
    ,IfcBuildingElementProxyType
    ,IfcChimneyType
    ,IfcColumnType
    ,IfcCoveringType
    ,IfcCurtainWallType
    ,IfcDoorType
    ,IfcFootingType
    ,IfcMemberType
    ,IfcPileType
    ,IfcPlateType
    ,IfcRailingType
    ,IfcRampFlightType
    ,IfcRampType
    ,IfcRoofType
    ,IfcShadingDeviceType
    ,IfcSlabType
    ,IfcStairFlightType
    ,IfcStairType
    ,IfcWallType
    ,IfcWindowType
    ,IfcToken))
 SUBTYPE OF (IfcElementType);
END_ENTITY;

ENTITY IfcToken
 SUPERTYPE OF (ONEOF
    (IfcTokenElementedCase))
 SUBTYPE OF (IfcBuildingElement);
    PredefinedType  OPTIONAL  IfcTokenTypeEnum ;
 WHERE
    CorrectPredefinedType  NOT(EXISTS(PredefinedType)) OR
 (PredefinedType  IfcTokenTypeEnum.USERDEFINED) OR
 ((PredefinedType = IfcTokenTypeEnum.USERDEFINED) AND EXISTS (SELFIfcObject.ObjectType));
    CorrectTypeAssigned  (SIZEOF(IsTypedBy) = 0) OR
  ('IFC4X1.IFCTOKENTYPE' IN TYPEOF(SELFIfcObject.IsTypedBy[1].RelatingType));
END_ENTITY;

ENTITY IfcTokenElementedCase
 SUBTYPE OF (IfcToken);
 WHERE
    HasDecomposition  HIINDEX(SELFIfcObjectDefinition.IsDecomposedBy)  0;
END_ENTITY;

ENTITY IfcTokenType
 SUBTYPE OF (IfcBuildingElementType);
    PredefinedType  IfcTokenTypeEnum;
 WHERE
    CorrectPredefinedType  (PredefinedType  IfcTokenTypeEnum.USERDEFINED) OR
((PredefinedType = IfcTokenTypeEnum.USERDEFINED) AND EXISTS(SELFIfcElementType.ElementType));
END_ENTITY;

[Thomas Krijnen]

Can you share the complete file? Maybe you inserted in the wrong place or something...

[Zhijian Jin]

Sure. I very apprieciate ur help, Thomas. Here is URL of my txt file. If u use ctrl+f to search "ifctoken" , u can find what i did. But not in browser, the search result in browser is not complete. Pls open and search "ifctoken" with Editor of windows.
https://drive.google.com/file/d/1FXCZP9NKRGv7UW5eFziPwwraRMAxdXT3/view?usp=sharing

[Thomas Krijnen]

For some reason your file starts with

(
Copyright by

but actually the original file starts with

(*
Copyright by:

(* is the start of a comment. So with that altered it tries to interpret the copyright text as the formal schema. You can use text based diff tools to see these differences between files.

[Zhijian Jin]

Hello, Thomas,

my Tutor has changed strategie. We will try to record our plan with property, no more with neu instance. So i don't need to creat new instance anymore. Thank u for ur informative and frendly help.