STEP Class Library ------ https://github.com/mpictor/StepClassLibrary

************************************************************************

Release 0.3 (Oct 29, 2011)

What's new since v0.2?

* Start using CTest

* Add a number of schemas, update IFC2X4 to RC3, update AP235 to TC

* Update the exchange file header schema to edition two; drop support

for N279 files

* In p21read, check that the schema name for the file and library match

* Fix bug with exchange files that contain strings ending in 'S'

************************************************************************

Release 0.2 (Oct 1, 2011)

What's new since v0.1?

* Retrieve aggregate type from the underlying type (issue #4)

* Fix aggregate select types naming convention in fedex_plus (issue #59)

* Fix several segfaults and double free's in p21read (issue #63)

* Fix several file read/write bugs in p21read, including

* don't write '$' for empty string

* 'abc\S\'def' is a valid string (issue #57)

* Improve p21read execution time

* Cleanup many files and delete src/clivfasd (but much more to do!) (issue #66)

* Add BNF files, schemas, and CAX-IF Part 21 files

For a detailed list of changes, see

https://github.com/mpictor/StepClassLibrary/wiki/changelog-v0.2

For a list of closed issues, see

https://github.com/mpictor/StepClassLibrary/issues?state=closed&milestone=2

************************************************************************

Release 0.1 (Sept 2011)

What's new since the SCL 3.2 release in 1998?

===========

* CMake build system replaces the configure script, Makefiles, and bash

scripts that were used by NIST. CMake is far easier to maintain and is

cross-platform.

* Support for formats that are no longer in the STEP standard

(ObjectStore, CORBA) has been disabled.

* Fix some bugs that were found when testing SCL with modern schemas,

including spaces inserted into function names and use of outdated

functions

* Bring SCL closer to alignment with modern coding standards - replace

String class with std::string, fix all GCC warnings

* Builds on Linux, OSX, and Windows; requires mingw on Windows.

* Add debugging option -d 9 -l nnn -u nnn to fedex_plus. This limits

parser debug output to a specified range of lines in the schema.

For a detailed list of changes, see

https://github.com/mpictor/StepClassLibrary/wiki/changelog-v0.1

For a list of closed issues, see

https://github.com/mpictor/StepClassLibrary/issues?state=closed&milestone=1

Pre-BRL-CAD changes:

* Patches from http://www.statik.tu-cottbus.de/fileadmin/project_dth/scl/

Jan 2005 - Mar 2006

* STEP Class Library Release 3.2 February 1998

* STEP Class Library Release 3.1 October 1997

* STEP Class Library and Data Probe release 2.1 June 1995

************************************************************************

************************************************************************

--Original NEWS file follows--

************************************************************************

************************************************************************

Updates from http://www.statik.tu-cottbus.de/fileadmin/project_dth/scl/

Jan 2005 - Mar 2006

The original SCL source distribution could not be cleanly un-archived

on case-insensitive file systems like Windows' NTFS because of a name

conflict.

SCL is mainly written in C++, but it also contains C sources, lex and

yacc sources (compatible to flex and bison) and csh and sh scripts.

The C++ sources, written in the 1990s, are not fully compliant to

ANSI/ISO C++. Updates have been made to base parts of SCL to ANSI/ISO

C++ (only the SPF interface, not the complete database system

interfaces or the dataprobe GUI). Some problems were also addresses

with newer UNIX-like systems.

There were also some issues with the configure script and some

makefiles which are addressed, as well as a new macro that is at

least required for gcc.

Remaing problem: The p21 file scanner of SCL currently

does not allow for comments within the parameter list of

data records. Only comments outside of data records are

accepted.

DISCLAIMER: Use at your own risk. These patches are

incomplete, may be incorrect, and are not endorsed

by NIST.

************************************************************************

What's New in the STEP Class Library Release 3.2

February 1998

mkProbe now prints a usage message showing allowable command line

arguments when it is run without arguments.

Extended the EXPRESS Pretty Printer:

- added command line options -a and -A to the exppp executable to

specify that the output should be alphabetized. Without the -a option

the order of the TYPEs and entities in the original EXPRESS is

preserved when pretty printing an EXPRESS file.

- Fixed a bug in the exppp toolkit where it would crash when handling

PROCEDUREs in EXPRESS.

- Extended the NIST Pretty Printer Toolkit to provide string and

buffer representations for EXPRESS USE and REFERENCE statements, and

for providing access to the EXPRESS SUPERTYPE statements.

Extended the STEP Class Library Toolkit capabilities including:

- adding additional dictionary constructs for representing EXPRESS:

SUPERTYPE statements, WHERE rules within entities, USE FROM clauses,

REFERENCE FROM clauses, global rules, PROCEDUREs, and

FUNCTIONS. Information about these objects is available but validation

based on it is not performed.

- enhanced fedex_plus C++ code generator to generate the necessary

dictionary objects for the above EXPRESS constructs for a particular

schema. Also enhanced schema dictionary code generation to add

information necessary to generate an EXPRESS schema (i.e. which

entities, types, global rules, USE and REFERENCE statements, etc are

associated with which EXPRESS schema dictionary object).

- added capability to generate EXPRESS from the above dictionary

constructs (e.g. USE, REFERENCE, global rules, functions, procedures,

etc.) and the existing dictionary constructs for EXPRESS schemas,

types, entities, and attributes.

- Fixed a bug in the casting functions for the classes handling

instances of SELECT TYPEs in EXPRESS.

e.g.

SdaiMeasure_value::operator SCLP23(Real)()

{

// was missing stmts such as these...

if( CurrentUnderlyingType () == config_control_designt_area_measure )

return _real;

if( CurrentUnderlyingType () == config_control_designt_context_dependent_measure )

return _real;

}

- Fixed an aggregate element TypeDescriptor (TD) pointer problem in

the dictionary. The TD pointer in the aggregate dictionary entry is

supposed to point at the TD representing the element type for the

aggregate. It pointed at the underlying or base type's TD (e.g. the TD

for STRING) instead of for the type which was specified in the EXPRESS.

For example where it should have pointed at a TD for a TYPE label -

where label is defined as TYPE label = STRING; END_TYPE - it pointed

at the TD for STRING. The TD for the aggregate element now points at

the TD for label.

- Fixed the casting operator for the class representing EXPRESS

enumeration types. It was returning the last element of the enum type

as the the default when the enum was unset. This choice predated enums

having an unset enum value. It now returns <enum_name>_unset as the

default when the enum is unset.

- cleaned up a bit of leaked memory. The memory leaked was mostly

handles to static memory.

- sdaiString not reading a value '' properly.

- sdaiString copy constructor mixing up undefined and unset values.

- dictionary objects handling and writing WHERE rule and UNIQUE rule

comments in EXPRESS. Added a data member

SCLstring _comment; // Comment contained in the EXPRESS.

to classes Where_rule and Uniqueness_rule. Also they have functions:

SCLstring comment_() const { return _comment; }

void comment_(const char* c) { _comment = c; }

to manipulate them. When writing EXPRESS for entities and types the

keywords WHERE and UNIQUE are only written if there are actual

rules. If there are only comments the keywords are written as a

comment.

**********************************************************************

What's New in the STEP Class Library Release 3.1

October 1997

The following is a list of enhancements which are found in the version

3.1 release of the SCL and Data Probe. It assumes you are familiar

with EXPRESS (ISO 10303-11). Familiarity with version 2.1 or higher

is a big plus.

-------------------

Easier Installation

-------------------

We created a script called configure using gnu's autoconf software.

The configure script is used to install the SCL release. Configure

automates the editing of multiple SCL files based on site-specific

information needed for installation. It performs checks against the

software and operating system environment to create a header file used

by SCL to handle commonly known software porting problem areas.

Finally, it builds all the SCL executables, scripts, and libraries.

Configure requires one command line argument specifying a name which

is used to create a directory. Configure installs the architecture and

environment specific SCL executables, scripts, libraries, and object

code is under this directory.

Configure accepts optional command line arguments to install the SCL

for use with optional software packages (like Orbix and/or

ObjectStore) and for use with different compilers on different

operating systems and/or machine architectures. Configure may be

executed several times to create several SCL builds under separate

architecture/environment specific directories. Each of these

directories is based on the same source code directory to minimize

space requirements. This is possible because the SCL source code was

created with preprocessor switches which allows the same source code

to be built for different purposes. Separate builds are also necessary

to use SCL with different C++ compilers since C++ object code is not

compatible between C++ compilers.

-----------------------------------------------------

Alignment with the C++ Binding (ISO 10303-23) to the Standard Data

Access Interface (SDAI, ISO 10303-22)

-----------------------------------------------------

SCL has been better aligned with the C++ binding (ISO 10303-23,

a.k.a. STEP Part 23) to SDAI. This has involved several name changes

for classes implementing base EXPRESS types and application-schema

defined EXPRESS types. The name changes were possible since these

types and classes have been moved to be encapsulated by a namespace

implemented via a struct definition. The namespace has been defined in

a way that offers great flexibility in avoiding name conflict with

other software packages (like X Windows, CORBA implementations, etc)

and your application code. The namespace name is easily changed if

necessary. As a result of adding a namespace a noticeable difference

in SCL use has occurred.

Use of underlying SCL classes and types are now wrapped in macros that

are defined in the file sclprefixes.h. This file is installed under

the arch directory which allows it to be adjusted as necessary for

each SCL software installation. For example, if a compiler or software

package has a problem handling the namespace mechanism via a struct

definition alternate macros can be used from the sclprefixes.h file

bypassing the namespace altogether. If a name conflict occurs when the

namespace is turned off macros can be used that add a name prefix to

SCL types and classes. Use of the macros when using SCL types and

classes is what allows for the flexibility in dealing with problem

areas when using SCL with other software.

An example of a name change and macro use: sdaiString has now become

SCLP23(String) which could translate to SDAI::String or SDAI_String

(depending on whether you use the SDAI namespace or not) or any other

namespace or prefix as is necessary. To change the SDAI namespace name

or prefix name the macro definition for SCLP23() could be changed in

the sclprefixes.h file.

The early bound access functions that are generated by fedex_plus from

EXPRESS defined entities have been updated to the latest version of

Part 23's C++ binding to SDAI. A previous early bound function defined

as "const SdaiLabel Name()" would now be defined according to Part 23 as

"const SdaiLabel name_()". *notice* that application schema defined

types are not yet defined in a namespace. Compatibility with previous

versions of SCL early bound functions has been maintained via the -a

fedex_plus option.

-----------------------------------------------------

SDAI Session Schema objects implemented (model_contents, extents, etc)

-----------------------------------------------------

Several classes and types defined as part of SDAI Part 23's Session

Schema have been implemented (where before they mostly had stub

functions). These have been implemented for use with or without the

ObjectStore object oriented database. Model_contents_<schema_name> is

now being generated by fedex_plus allowing Entity_extents to be

maintained for entities as desired.

-----------------------------------------------------

Object Oriented Database Capability Using ObjectStore

-----------------------------------------------------

SCL has been enhanced to optionally use the object oriented database

ObjectStore from ODI. The INSTALL file describes how to build the SCL

libraries for use with ObjectStore. The SCL libraries built for use

with ObjectStore may then be used to create persistent or transient

SCL objects. The transient objects use the ObjectStore transient

database.

The SCL application, fedex_os, uses an application schema written in

EXPRESS to generate additional code needed for use with ObjectStore.

Fedex_os is used in conjunction with fedex_plus for generating the C++

necessary to implement your application schema.

Although building SCL libraries for use with ObjectStore is

documented, instructions for building your application with SCL

libraries and ObjectStore is as of yet undocumented. The undocumented

steps for building an SCL/ObjectStore application are the steps

required to build any ObjectStore application. A person familiar with

building ObjectStore applications should be able to create a Makefile

able to perform these necessary steps.

A good starting point for creating a Makefile suitable for building an

SCL/ObjectStore application would be the Makefile generated using the

mkProbe script. The configure script (executed with the ObjectStore

options) generates a make_rules file which contains the necessary

Makefile macros for using ObjectStore. The mkProbe generated Makefile

already includes this make_rules file. The Makefile is set up to build

a simple application which uses the appropriate SCL and ObjectStore

libraries. The Makefile rules for building this application could be

used as a starting point for creating Makefile rules to build your own

SCL/ObjectStore application. (The example application code is not set

up to use ObjectStore.) Additional steps would need to be added to run

the ObjectStore schema generator (ossg), link with the additional

application-specific ObjectStore object files, run os_postlink, etc.

-------------------------------------------------------

Use of Orbix with SCL for Developing CORBA Applications

-------------------------------------------------------

SCL has been enhanced to be able to use Orbix for developing SCL

applications for use within the Common Object Request Broker

Architecture (CORBA). CORBA is used to provide an architecture for use

of objects within a distributed environment. Distributed communication

occurs by client applications communicating with servers through

Object Request Brokers (ORBs). Clients may be written to use any

number of programming languages provided the CORBA software vendor

(Orbix in this case) supports the language. We have only tested

clients written using C++. We may soon test JAVA clients.

The SCL application, fedex_idl, is used to create an Interface

Definition Language (IDL) schema from your application's EXPRESS

schema. The generation of IDL schemas by fedex_idl is according to

STEP's Part 26 Interface Definition Language binding to the SDAI. The

Orbix IDL compiler is then used to generate the client and server code

necessary for communication through an Orbix ORB. The SCL application,

fedex_plus, would then be run with the -c option on your application's

EXPRESS schema to generate the server implementation objects required

to build an Orbix server (it uses the TIE approach). You would be

required to write the C++ main() function for the server code.

Although building SCL libraries for use with Orbix is documented,

instructions for building your application with SCL libraries and

Orbix is as of yet undocumented. The undocumented steps for building

an SCL/Orbix application are the steps required to build any Orbix

application. A person familiar with building Orbix applications should

be able to create a Makefile able to perform these necessary steps.

A good starting point for creating a Makefile suitable for building an

SCL/Orbix application would be the Makefile generated using the

mkProbe script. The configure script (executed with the Orbix options)

generates a make_rules file which contains the necessary Makefile

macros for using Orbix. The mkProbe generated Makefile already

includes this make_rules file. The Makefile is set up to build a

simple application which uses the appropriate SCL and Orbix

libraries. The Makefile rules for building this application could be

used as a starting point for creating Makefile rules to build your own

SCL/Orbix application. (The example application code is not set up to

use Orbix.) Additional steps would need to be added to build the

additional server code you would need to write, register the server

with Orbix, build and link with the IDL compiler generated code, etc.

-----------------------------------------------------

Use of Orbix and ObjectStore with SCL

-----------------------------------------------------

SCL has been enhanced to be able to be used with Orbix and ObjectStore

providing a persistent server for use within a distributed CORBA

environment. We have used SCL in this way for two NIST projects: the

National Industrial Information Infrastructure Protocols project and

the National Advanced Manufacturing Testbed Framework project.

Once again, although building the SCL libraries for use with Orbix and

ObjectStore is documented (via installation using the configure

script), instructions for building your application to use Orbix and

ObjectStore is as of yet undocumented. See the previous two sections.

-----------------------

MULTIPLE SCHEMA SUPPORT

-----------------------

A library and Data Probe can now be generated for an EXPRESS file

containing multiple schemas. This is done primarily by dividing the

source code generated by fedex_plus into separate files. Separate

files are generated for each schema contained in the EXPRESS file. In

addition, often schemas are dependent on one another. This will be

the case if the schemas use and reference entities and types from each

other. If, for example, entity X in schema A is a subtype of entity Y

in schema B, X will not be processed until B in schema Y is processed.

Other such cases of interdependence occur if an entity in schema A

contains as an attribute an enumeration or select type defined in

another schema. To address such cases, fedex_plus may process a

schema in multiple passes. At each pass, only the objects in the

schema which are not dependent on not-yet-processed objects in other

schemas are processed. At each successive pass through the schemas as

more and more objects are processed, more and more dependent entities

will become processable. Certain schemas may require three passes or

more in cases of chains of dependence (such as A being a supertype of

B which is a supertype of C, etc.).

For an EXPRESS file with multiple dependent schemas, it is advisable

to organize the file with bottom-up design. Schemas containing the

simpler, building block types and entities should appear first. By

doing so, when fedex_plus begins processing the more complex schemas,

there will be fewer cases in which the parser will encounter not-yet-

defined objects from other schemas. (The objects which are referenced

the most will have already been defined.) This will minimize the

number of times fedex_plus is required to divide output files.

One known case of interdependence which fedex_plus is not able to

support occurs if say select A has select B as an item, and select B

has select A as an item. (This is unsupported even if A and B are in

the same schema.) fedex_plus has no way in which it can generate

compilable source code for the selects because each is dependent on

the other. In addition, this would cause the parser to fall into an

endless loop, so we strongly discourage it. ;-)

------------------------------

USE / REFERENCE CLAUSE SUPPORT

------------------------------

The SCL also partially supports the EXPRESS concepts of USE and

REFERENCE. According to the rules of EXPRESS, schema A may reference

objects from schema B by way of a USE or REFERENCE clause (U/R). Any

object which is not U/R'ed from schema A to B, directly or indirectly,

is not visible to B. The SCL does not support the hiding of objects

between schemas. Basically, an object defined anywhere in the SCL is

visible everywhere else. What is supported is renamings of objects

between schemas. Say schema B uses entity X from schema A and renames

it to Y (i.e., "USE from A (X as Y);"). If a Part 21 file is read in

or written out using the SCL or the Data Probe, if the "current"

schema is defined to be B, the renamings defined by B's U/R statements

will be used. The "current" schema is set according to the first

schema listed in the FILE_SCHEMA section of the Part 21 file's header

section. (It is assumed that I/O is being done with the SCL's

STEPfile object.) If no current schema is defined, all possible

entity and type names are recognized in file reading, and the original

names only are used in writing.

As mentioned above, the SCL does not support the hiding of objects of

say, schema A, which are not U/R'ed by schema B. Thus, it's possible

to use the SCL or Data Probe to read or write a Part 21 file in which

A is the current schema and which contains instances of entities which

are not U/R'ed by A. This will not be flagged as an error.

The U/R clause is more poorly supported by the Data Probe. When the

Probe displays instances of entities, only their original names are

displayed. (This also applies when an entity has a select attribute

and the current choice of the select is being displayed by name. For

example, if a select is set to HEIGHT(35), the original name of

`HEIGHT' is displayed even if we're in schema B which renames HEIGHT

to LENGTH.) When a user is using a <<step entity editor window>> to

create an instance of an entity, all possible names for a type are

recognized. This includes the original object name plus all names

given to it by other U/R'ing schemas, regardless of the current

schema.

Another shortcoming with the U/R support is related to the fact that

the SCL does not allow objects of the same name in different schemas.

For this reason, U/R support is also limited to cases where the new

name is unique within the entire EXPRESS file.

Lastly, the U/R support is unable to deal with aggregate types of

two or more dimensions. Say we were attempting to instantiate a 2D

aggregate of selects. Type names will appear in the inner select

instantiations, and they should be set according to the current

schema. However, since the SCL currently does not fully support

higher-dimension aggregates (it uses the SCLundefined class and

considers the entire instantiation a string), it's impossible to

verify the values within the aggregate instance.

----------------------

COMPLEX ENTITY SUPPORT

----------------------

By complex entity, I mean ones which require external mapping (see Part 21,

section 11.2.5).

New Features

------------

(I really think the structures and functions I used to support this

are a recursive work of art. Too bad it's all invisible to the user.)

1. The primary enhancement now included is the checking of the

legality of complex entities. If a user attempts to initialize a

complex entity (class STEPcomplex), the SCL will determine, based on

the supertype and subtype information of the EXPRESS, if the entity

represents a legal combination of entities. If not, an error message

will be issued, and a complex entity will not be created. Formerly,

the SCL would only check if the entity names themselves were valid and

not worry about the combination.

2. Non-independent entities cannot be instantiated. These are

entities which cannot be created without external mapping. Say we

have,

ENTITY A SUPERTYPE OF (B AND C);

The SCL would not accept an instantiation statement such as,

#11=C(xx,yy,...);

C requires external mapping since it can only exist together with B,

in a statement such as,

#11=(A(...)B(...)C(...));

If a user attempts to create a C with internal mapping using the

STEPfile object (the class which handles all reading and writing of

Part 21 files within the SCL), an entity will not be created and an

error message will be issued. The SCL behaves similarly if a user

attempts to create an instance of an abstract supertype.

The above behavior is also reflected in the Data Probe. All entities

which are abstract supertypes are marked with an `*' (as in SCL vn.

2.1). Entities which cannot be instatiated without external mapping

are marked with a `%'. Neither can be created using the Data Probe.

(The Probe does not have the capability of creating complex entities,

see below, next section.)

(Note: A user can instantiate an entity such as C from the STEPentity

level, bypassing STEPfile. STEPentity will allow the initialization

but will place a warning in its errorDesc field.)

3. fedex_plus may be compiled with the flag COMPLEX_INFO. If this

flag is turned on, fedex_plus prints out (to `cout') a large amount of

detail on the complex entities it finds and their overall structure.

This is useful to see how fedex interpreted the complex information of

an EXPRESS file, and to get a simple graphical view of the supertype-

subtype hierarchy of the file.

fedex_plus's makefile contains the commented-out line,

#USER_DEFS = -DCOMPLEX_INFO

If this line is uncommented, a fedex_plus executable will be built

which prints such information.

Limitations

-----------

1. As in multi-schema support (above), complex entity (CE) support is

not completely reflected in the Data Probe. This may be seen in a

number of instances (you can skip this if you don't intend to use the

Probe):

(a) It's impossible to create an instance of a CE using the Data

Probe. (See point #2 under "Complex Entity Support").

(b) The Data Probe is able to correctly read a CE from a Part 21 file,

and place a copy of it in the Entity Instance List Window. It also

allows the user to edit the values of the entity's attributes by

selecting the entity (from the Ent Instance List Win) and creating a

STEP Entity Editor Window. The Data Probe, however, does not accu-

rately display the type information of the CE (in the Type Information

Window). What it does do is takes the name of the 1st entity in the

list (CE entity names are displayed alphabetically) and shows the type

info for that entity.

2. The SCL does not read partial complex instances. Generally, if a

single entity-member of a complex entity has an error, the entire rest

of the complex entity will be skipped.

3. If entity members of a complex entity have been renamed (through

the EXPRESS USE/REF clause - see previous section), they are read and

written properly. However, the SCL may not write the members of the

CE in alphabetical order (as required by Part 21, sect 11.2.5.3). The

individual entities are sorted according to their original names. If

the renaming of an individual entity places it out of order, the nodes

will be printed out of order.

4. "Diamond inheritance" is not handled automatically and must be

fixed by hand in the code generated by fedex_plus. (See

whatsnew.2-1.txt, section "Multiple Inheritance".)

5. Selects between aggregates: A select containing two aggregate

choices of the same type (e.g., ARRAY and ARRAY, as opposed to ARRAY

and SET) will cause fedex_plus to generate code which cannot be

compiled.

6. Problem with sparcworks compiler version 4.0(?) - operator int() =

op enum(). This happens in the following case... Both functions,

however, are required by Part 23. We fixed this by removing enough

functions for it to build. We were not sure if this error is the fault

of the sparcworks compiler or is a problem with the standard.

!!!!!!!!!!!!!!!!!!!!!!!!!!!!DISCLAIMERS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Names of companies and products are provided in order to adequately

specify procedures and equipment used. In no case does such

identification imply recommendation or endorsement by the National

Institute of Standards and Technology, nor does it imply that the

products are necessarily the best available for the purpose.

NO WARRANTY

===========

NIST PROVIDES ABSOLUTELY NO WARRANTY. THE NIST STEP TOOLKIT

IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER

EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.

THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS

WITH YOU. SHOULD ANY PORTION OF THE NIST STEP TOOLKIT PROVE DEFECTIVE,

YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR, OR CORRECTION.

IN NO EVENT WILL NIST BE LIABLE FOR DAMAGES, INCLUDING ANY LOST

PROFITS, LOST MONIES, OR OTHER SPECIAL, INCIDENTAL OR CONSEQUENTIAL

DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE (INCLUDING BUT NOT

LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE, OR LOSSES

SUSTAINED BY THIRD PARTIES, OR A FAILURE OF THE PROGRAM TO OPERATE

WITH PROGRAMS NOT DISTRIBUTED BY NIST) THE PROGRAMS, EVEN IF YOU HAVE

BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES, OR FOR ANY CLAIM BY

ANY OTHER PARTY.

**********************************************************************

What's new in the STEP Class Library and Data Probe release 2.1

June 1995

This release of the STEP Class Library (SCL), fedex_plus code

generator, and Data Probe also contains the latest releases of the

fedex syntax and semantic checker, the NIST Express Toolkit (also new

on SOLIS as of June 12, 1995), and the Express Pretty Printer Toolkit.

The NIST Express Toolkit and fedex have been updated to handle the IS

version of Express and various problems have been fixed as a result of

pre-validation conformance testing. Following is an overview of

what's new in the STEP Class Library (and hence fedex_plus) and the

Data Probe.

--------------------

*Compilers supported:

--------------------

The SCL and Data Probe now compiles with gnu C++ v2.5.8, v2.6, and

Sun C++ v3.0.1. The SCL also compiles with ppCC, the pre-processor of

the Open OODB from TI.

-------------------

*Complex Instances:

-------------------

The SCL now supports instantiation of complex instances via a class

called STEPcomplex. The SCL supports reading and writing of complex

instances from/to Part 21 and Working files using the external mapping

specified in Part 21.

Complex instances are created by calling the constructor for

STEPcomplex with a list of entity name strings. The combination of

entity names that are passed in to become part of the complex instance

are not validated to determine if they are a legal set of entities

with regard to the inheritance structure specified in Express.

Attributes within each of the represented entities are validated as

usual.

An entity hierarchy with triangle and circle both inheriting from

shape with andor inheritance would allow creation of a

circle-shape-triangle entity. Here is an example of how such an

object could be created.

SCLstring *entNmArr[64]; // array of entity type names

int fileid = 1;

Registry *registry = new Registry(SchemaInit);

entNmArr[0] = new SCLstring("shape");

entNmArr[1] = new SCLstring("triangle");

entNmArr[2] = new SCLstring("circle");

entNmArr[3] = 0;

STEPentity * obj = new STEPcomplex(&_reg, (const SCLstring **)entNmArr,

fileid);

In the same manner the toolkit would allow a user to create a

circle-shape-triangle-color entity even if it was not valid given the

Express.

The complex instances implementation has a late bound flavor. The

instances do not have code generated implementing attribute access

functions with names matching the name of the attribute. This method

of access, normally associated with an early binding, is available for

non-complex instances and is partially available for instances

involving multiple inheritance. The complex entity instance's

attributes are accessible through the STEPattribute class in a manner

similar to the non-complex instances.

The Data Probe reads and writes complex instances from/to Part 21 and

Working files but supports very limited editing of complex instances.

----------------------

*Multiple Inheritance:

----------------------

The SCL offers two choices to users in handling multiple inheritance.

These include the method offered by SCL in previous releases and the

current method. The current method handles attributes inherited from

all parents. It does not correctly handle multiple inheritance where

an entity has more than one path through parents to a common ancestor.

One could imagine this case as a diamond shaped inheritance structure.

When this case of multiple inheritance is encountered attributes are

duplicated. This case of multiple inheritance may possibly be

avoided by modifying the EXPRESS schema by breaking some links in the

inheritance hierarchy. This will not have an adverse affect on the

implemementation. The user may choose to use the current or previous

method of handling multiple inheritance. The current method is the

default behavior. The previous method is obtained by supplying the

-s (or -S) option with the fedex_plus code generator or the mkProbe

script.

When the fedex_plus code generator is generating the C++ class library

representation of a schema, it outputs information calling attention

to the cases of multiple inheritance.

The previous method of handling multiple inheritance:

This method of handling multiple inheritance is useful where

attributes are inherited from only one parent. It does not allow an

entity instance to be casted in C++ to a class representing

non-implemented parents. These multiply inherited instances are

created in the same manner as non-multiply inherited, non-complex

instances.

For each entity that has multiple parents the first parent that

contains or inherits attributes is used in the inheritance hierarchy

for the C++ class representing the entity. In each case of multiple

inheritance the parents are searched for attributes in the same order

as they were specified for the entity in Express. Once attributes

have been found associated with one parent, attributes from other

parents are ignored. All attributes handled have access functions.

The current method of handling multiple inheritance:

Multiply inherited instances are created in the same manner as

non-multiply inherited, non-complex instances. These include calling

any of the following functions:

1. the constructor of the entity class.

2. Registry::ObjCreate() with the name of the entity as a string argument.

3. EntityDescriptor::NewSTEPentity() from the dictionary entry

associated with the entity to be created.

a c e

| | | This hierarchy modeled in Express turns into

b d f the data structures pictured below.

\ | /

\ | / h

\|/ /

g -

Each STEPentity also has a pointer back to g's STEPentity.

STEPentity STEPentity STEPentity

-------------------- -------------------- --------------------

| - attribute list | | - attribute list | | - attribute list |

| for a, b, c, d,| | for c and d | | for e and f |

| e, f, h, and g | | (in that order)| | (in that order)|

| (in that order)| | | | |

| - pointer to | | - pointer to | | - pointer to |

| STEPentity ----+--->| STEPentity ----+--->| STEPentity ----+----

| - pointer to | | - pointer to | | - pointer to | |

| dictionary | | dictionary | | dictionary | |

| entry for g | | entry for d | | entry for f | |

-------------------- -------------------- -------------------- |

| | | |

a c e |

---------------------- ---------------------- ---------------------- |

| - attributes for a | | - attributes for c | | - attributes for e | |

| - access functions | | - access functions | | - access functions | |

| for a | | for c | | for e | |

---------------------- ---------------------- ---------------------- |

| | | |

b d f |

---------------------- ---------------------- ---------------------- |

| - attributes for b | | - attributes for d | | - attributes for f | |

| - access functions | | - access functions | | - access functions | |

| for b | | for d | | for f | |

---------------------- ---------------------- ---------------------- |

| |

g |

---------------------- |

| - attributes for g | |

| - access functions | |

| for g | |

---------------------- |

|

STEPentity <-----------

--------------------

| - attribute list |

| for h |

| - pointer to |

| STEPentity |

| - pointer to |

| dictionary |

| entry for h |

--------------------

|

h

|

----------------------

| - attributes for h |

| - access functions |

| for h |

----------------------

Multiply inherited entities have two early bound access functions

associated with all of the attributes - one for get attribute value

and one for set attribute value. These access functions have the same

name as the attribute. The requirement for use of these access

functions is that they must be called from the appropriate part of

the data structure representing the multiply inherited instance. C's

attribute access functions could be called from a pointer to the C or

D part of the data structures shown above. Functions are supplied for

accessing the appropriate part of the data structure.

a

/ \ An Express schema containing this type of inheritance hierarchy

| | under the current multiple inheritance implementation will cause

b c attributes for 'a' to be duplicated.

| |

\ /

d

The Data Probe fully supports the SCL implementation of multiply

inherited entity instances. Inside a STEP Entity Editor window,

attribute dictionary information is displayed as usual for all

attributes in multiply inherited entity instances. It currently,

however, only displays the first parent encountered each step up the

parent hierarchy when displaying Express dictionary information for

the entity as a result of pressing the Type Information button.

------------------

*Part 21 Comments:

------------------

The SCL now handles comments associated with Part 21 and SCL Working

files. It saves comments preceding an entity instance with the entity

instance that follows. It can handle saving all the comments in the

example below. All the comments would be saved as part of entity

instance #1.

/*comment 1*/ /*cmt 1.5 */

#1/*cmt 2*/=/*cmt 3*/ORGANIZATION/*cmt 4*/( 'hi','foo','bar')/*cmt 5*/;/*cmt6*/

#2=ORGANIZATION('ab','cd','ef');

When writing instance #1 above to a Part 21 or Working file, all

comments that have been saved with the instance will be written out

separately preceding the instance as follows.

/*comment 1*/

/*cmt 1.5 */

/*cmt 2*/

/*cmt 3*/

/*cmt 4*/

/*cmt 5*/

#1=ORGANIZATION('hi','foo','bar');

/*cmt6*/

#2=ORGANIZATION('ab','cd','ef');

Part 21 comments are also read and written for header entity instances.

Part 21 comments are supported in the Data Probe. Comments associated

with an entity appear in the comment field on the STEP Entity Editor

window. The comment (formerly "label") field accepts comments that

will be saved to a Part 21 or Working file and comments that are not.

Comments written as valid Part 21 comments (i.e. enclosed in /* */)

will be saved in files. Non-Part 21 text will only last until the end

of the Data Probe session or until the entity is deleted, whichever

comes first.

---------

*Selects:

---------

The way SCL handles selects for editing and writing part 21 files has

been updated. Here are the new rules.

- If there is only one choice in the select (i.e. a select of one

type), the value for that choice can be entered without qualification.

- If the select is between entities only (and not via nested selects),

the element types are assumed to be unique and values can be entered

as a reference to an entity instance.

- In all other cases the value must be qualified by enclosing the

value in the type of the select item.

- These rules apply to editing in the Data Probe, as well as reading

from and writing to a file.

When editing a select attribute in the Data Probe STEP Entity Editor

window, mouse clicking the edit button offers support for qualifying

the select attribute value. When you click the edit button for a

select attribute, and choose a type from the list, it is applied to

the attribute value field in the entity editor.

If there wasn't a value in the attribute previously, then the field will

contain just the type specifier, e.g., Str1() if Str1 is the type selected.

If a value exists in the field, it is modified to accomodate the new

specifier. This means the following:

o If the value in the field starts with a single-quote ('), it is

assumed to be a string literal, and is completely wrapped in the new

specifier (e.g., 'foobar' --> Str1('foobar') ).

o If the value starts with an open-paren ('('), it is assumed to be an

aggregate literal, and is wrapped in the new specifier as above.

o If the value already has a specified type (e.g., Str1('foo')), things

get interesting. (By the way, containing a specified type is

determined by the existence of an open paren (after the first

character) encountered before end-of-string.) Ordinarily, the

type specifier is replaced by the new type, e.g.,

Str1(.enumval.) --> Enum1(.enumval.).

However, if the new type is a SELECT, then the whole value in the

field is wrapped in the new type specifier, e.g., Str1('foo') -->

Sel1(Str1('foo')) if the new type is Sel1. This is because it is

assumed that the user is qualifying the subtype of the SELECT before

'editing'. A possible future enhancement may check to see if

the field contains a valid select subtype, and if not, do a

replace as in the above Str1->Enum1 example.

If the field entry matches none of these cases, it is just wrapped in the

type specifier... actually, the only real reason for having the string

and aggregate special cases is that they contain (or can contain)

parentheses that would throw off checking for type specifiers...

Validation of all of this still occurs in the editing window as usual,

so if the user chooses something invalid, it is still flagged in the

STEP Entity Editor window.

---------

*Strings:

---------

Strings can now differentiate between a string that does not exist and

a string that has no elements. This may be done with the following

functions in the SCLstring class in scl_string.h:

// returns 1 if _strBuf is a null ptr or if it is an empty string (i.e. "")

int is_null() const;

// returns 1 if _strBuf is a null ptr, and 0 otherwise

int is_undefined() const;

// deletes _strBuf

void set_undefined() ;

// zeroes out space in _strBuf

int set_null() ;

The Data Probe now differentiates between a STRING attribute value

that does not exist and one that exists but contains no characters.

When editing an attribute of type string in a STEP Entity Editor

window, an attribute value containing only a dollar sign indicates that

the string attribute value does not exist. An attribute value

containing only a backslash followed by a dollar sign indicates a

string value of length one containing a dollar sign. The absence of a

value indicates that the string exists but contains no characters.

-------------

*Enumerations:

-------------

The access functions for enumerations now accept the associated C/C++

enumeration value rather than the enumeration class. Implicit calling

of casting functions makes it possible for instances of the

enumeration class still to be passed into the attribute's get

functions and to be assigned the return value of the attribute's put

functions.

--------

*Boolean:

--------

Attributes of type Boolean and aggregate of Boolean were previously

implemented using the Logical and Logicals classes (respectively).

The fedex_plus code generator now generates classes Boolean and

Booleans to implement attributes of type Boolean and aggregate of

Boolean respectively.

--------------------------------

*Public Data Member Name Changes:

--------------------------------

In class STEPentity:

Descriptor is now eDesc

In class STEPattribute:

Descriptor is now aDesc

The name change in STEPentity was to avoid symbol name conflicts of

STEPentity::Descriptor with access functions generated for Express

entity attributes named descriptor. The new name will not be

conflicting with any generated names since the letter case will never

match.