Introduction and Overview of STEP
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About AP 210
STEP Application Protocol (AP) 210 (Electronic assembly, interconnect, and packaging design) provides the data structures for the exchange of electromechanical design, requirements, functional specification, and configuration identification with configuration control data either with or without associated 2D or 3D model information. Included within functional scope are netlists, explicit interconnect layout and material stackup and associated assemblies, including higher level assemblies. This international standard was developed under the auspices of the International Organization for Standardization (ISO) and is one of a series of parts comprising the full Standard for the Exchange of Product model data (STEP) standard known as ISO 10303.
AP 210 was developed to represent the domain which is described in its scope section, and is centered on the requirements definition/design/analysis/manufacturing phase of electromechanical products. For purposes of this AP, electromechanical products are those products for which a design flows requires detailed definitions to co-exist in the electrical functional space, the electrical layout space, the mechanical functional space, and the mechanical layout space.
Using This Document
The purpose of this document is to provide a usage guide for industry and to ensure the consistency of mappings to the AP 210 schema from existing software application data structures, other Application Protocols, and related industry standards. This document assumes that the reader has at least a rudimentary knowledge of both AP 210 and its associated application domain (for basic conceptual information on AP 210, see the AP 210 Concept of Operations). The figures in this document are intended to provide a navigational view of portions of the AP with boxes representing entities, lines being relationships, and arrow heads (or bubbles) indicating the direction of dependency. An entity "points to" other entities upon which it is dependent. The arrow head or bubble is on the end adjacent to the supporting entity. See ISO 10303-11 annex D for more information.
This document will provide pre- and post-processor recommendations where attributes from the conceptual STEP data models may not actually have values in the AP 210 application domain, as documented in AP 210. The terms pre-processor and post-processor refer to the applications which write and read the AP 210 data respectively. In these recommendations, the term "no standard mapping" means there is no mapping defined in the AP's ARM to AIM mapping table for the data. The term "no standard string" means that either:
- there is no documented consensus on string values defined in the AP's ARM to AIM mapping table,
- there is no rule in the AP's AIM to constrain the allowed values.
This document is not intended to replace the AP ARM to AIM mapping table specified in clause 5 of AP 210 or the requirements specified in clause 4 of AP 210 or the rules specified in clause 5 of AP 210.
General STEP Application Guidelines
There are some constructs which have global applicability across all data in a STEP exchange. These constructs relate to the file header for physical file exchanges, data definitions within the file related to the AP itself, and fundamental constructs which contain the information for people, organizations, dates, times, approvals, security classifications, and units of measure. References to ISO 10303 documents herein are to the latest available unless otherwise specified, and include any technical corrigendum announced. Refer to the following URL for currently available editions: SOLIS ....
The STEP Physical File
One way to externalize AP 210 data is via a physical file which is an ASCII encoding of the data based on the EXPRESS constructs in AP 210 as mapped through ISO 10303-21. This document will not deal with this in any detail. The user is referred to ISO parts 10303-11 for definitions of EXPRESS constructs and 10303-21 for information on how to map the EXPRESS constructs in AP 210 to the physical file. (See ******* for implementors agreements that affect physical files.) Public domain toolkits and commercial software are available to automate the task. See the following URLs....NIST/EPM/STEP Tools/ProStep. This document does not form an endorsement of any vendor offering.
Post-processor Recommendations: When reading a physical file, post-processors should note all errors found during the reading of the file. It is recommended that post-processors provide options to the user on whether to continue when an error is encountered. There are no recommendations on what a post-processor should do with erroneous data. This is left to the discretion of the implementor. If the implementor elects to correct erroneous data, the post-processor should inform the user (as above) of the erroneous data and what correction was made.
The STEP SDAI
The other way to externalize AP 210 data is via an SDAI interface which is a procedural interface based on the EXPRESS constructs in AP 210 as mapped through ISO 10303-22 and one of ISO 10303-23 through ISO 10303-26. "C", "C++", Java, IDL bindings are currently available. The document will not deal with this in any detail. The reader is referred to the above documents for information on how to map the EXPRESS constructs in AP 210 into a specific SDAI implementation. Public domain and vendor supplied toolkits are available to automate this task. The previously specified URLs also provide links to support SDAI implementations.
SDAI Read Recommendation: When extracting data from a database, processors should note all errors found. It is recommended that processors provide options to the users on whether to continue when an error is encountered. There are no recommendations on what a processor should do with erroneous data. This is left to the discretion of the implementor. If the processor elects to correct erroneous data, the processor should inform the user (as above) of the bad data and what correction was made.
The W3C XML
Currently various research activities are underway to determine the optimal way to externalize AP 210 data over the web using XML. This document will be updated as a consensus develops.
AP Identification and Contexts
STEP is a standard information model that supports application to application communication. For application to application communication to be successful a common context must be established. As such the representation of the data for an AP identifies the AP data structure through computer sensible data. This is done through the entities application_context and application_protocol_definition. These and related entities are described pictorially in Figure 1.
The application_context entity identifies the application which defined the data. The application attribute, based on its definition in ISO 10303-41, should have the value "electronic assembly interconnect and packaging design" as this is the application domain AP 210 is meant to cover.
Note: industry usage may indicate this is equivalent to the broader electro-mechanical design or electronic packaging design.
The application_protocol_definition entity further identifies the AP. For AP 210, the status attribute, based on its definition in ISO 10303-41, should have the value "draft international standard". The application_interpreted_model_schema_name attribute should have the value "electronic_assembly_interconnect_and_packaging_design" based on an AP 210 restriction. The application_protocol_year attribute should have the value "1998", based on its definition in ISO 10303-41.
The application identified by the application_context entity is broken down into elements in STEP. In AP 210, these elements are contexts. For AP 210, the valid context entities are product_context, product_definition_context, and product_concept_context. Figure 1 illustrates product_context. Figure 2 illustrates product_definition_context. For clarity, some of the entities required to establish the relationships from the following entities are not included: person_and_organization, security_classification, approval.
