Business overview

This section provides a business level overview of this capability.

Reference data are terms and definitions that have to be mutually understood by all parties involved in an information exchange.

Reference data are used to extend and to tailor the data model to meet the requirements of different groups of users and provide greater precision.

Information model overview

This section provides an overview of the information model that supports this capability.

Reference data is applied using the Classification assignment and External class modules. The main entities used by this capability are shown in figure 1 below.

Figure 1 —  Express-G diagram, Main entities used by this capability

The reference data being applied are defined in external sources such as databases, web-sites, published documents etc. The source used for a particular instance of reference data shall be stated in the id attribute of the External_class_library entity. The identification may be a URN, URL, Document identification or any other identification that uniquely identifies the source. A complementary decription of the source may be provided using the External_class_library  description attribute.

The reference data being applied shall be stated by name using External_class and its inhereted attribute name. In situations where a reference data class is uniquely identified by code, number, URN etc, rather than by name, the id attribute of External_class should hold the value of the identified class in the external class library.

The relationship between the reference data and the entity being described/classified is established using Classification_assignment.

Figure 2 —  Applying reference data example

In the example above the identifier "TYRES-010101" is classified as being a "Part identification code" (urn:plcs:rdl:std:Part identification code) as defined in the PLCS standard reference data library (RDL) available on the the web via the URN "urn:plcs:rdl:std".

Model Characterization

This section specifies how the information model can be further characterized by the assignment of additional information such as dates, approvals and people or organizations.

The following characterizations may apply.

Characterization: Assigning PLCS Superclass (Optional)

This capability does not require any further characterization of the introduced entities. However, there is a requirement for decribing how to exchange information on reference data class hierarchies (superclasses).

The PLCS reference data has been designed to be extensible. A set of base classes are provided and these can be extended by organizations or industry to fit particular business needs. The extension is done by creating subclasses of the base classes and storing these in a business specific reference data library (RDL).

For example, a Part must have at least one identifier assigned (Identification_assignment) that is classified as a "Part identification code" (urn:plcs:rdl:std:Part identification code) in order to represent the part number. The class "Part identification code" (urn:plcs:rdl:std:Part identification code) is defined within the PLCS reference data library. However, an organization may specify their own encoding system for parts, so that they can identify parts with their own identifiers (i.e. an organization specific part identification code). For example, an organization may create a class "My_org_part_identification_code" for this purpose. This class is then a subclass of "Part identification code" (urn:plcs:rdl:std:Part identification code) (or subclass thereof). This is illustrated below.

Figure 3 —  Organization specific reference data

A system reading a PLCS data exchange file that contains parts identified by "My_org_part_identification_code" may need to deduce that these are in fact "Part identification code" (urn:plcs:rdl:std:Part identification code)s. To correctly read the file the system therefore has to have access to the class hierarchy information stored in a business specific RDL. However, it may be the case that a system reading a file does not have access to this business specific RDL containing the definition of the business specific class and its relationship to the PLCS classes.

To allow for this, whenever non standard reference data is used, i.e. reference data that has not been registered as part of the PLCS reference data, the non standard class shall be defined as a specialization of the first (leaf) PLCS class extended in the PLCS RDL. In this case, the class "My_org_part_identification_code" shall be defined as being a specialization of "Part identification code" (urn:plcs:rdl:std:Part identification code).

The class hierarchy is represented using Subset, where superclass is represented as the External_class being subject of the superset attribute, and the subclass is represented as the External_class being subject of the subset attribute.

The instance diagram below shows the assignment of business specific reference data, "My_org_part_identification_code" identifier to a part, and at the same time providing a reference back to the leaf superclass defined within the standard PLCS reference data library.

Figure 4 —  Assignment of non standard classes.

Additional usage guidance

This section describes additional usage guidance where the PLCS data model provides abilities closely related to the scope covered by this capability.

Classification vs usage of Qualified_property_value_representation

Do not use Qualified_property_value_representation

Use Assigned_property, Activity_property or  Resource_property together with  Classification_assignment.

Classification vs usage of role attributes

Never use the role attribute for any entity.

Role attributes should be left empty. Role information should be defined using Classification_assignment.

Attribute classification

There is also a module Attribute classification defined within the PDM modules that can be used for classification. The module is provided for backwards compatibility with the PDM Schema(http://www.pdm-if.org/). However, this module shall not be used.

Classification not known

In cases where classification is expected but the sending application does not contain the information on how to classfy, this shall be resolved by the usage of the PLCS standard class [Unknown]
Error RDL1: The class Unknown does not exist in RDL at URI urn:plcs:rdl:std. Check the dexlib/data/refdata/rdl_index.xml
.

Capability templates

The following sections define a set of templates for the capability, where a template is a specification of a set of entities that need to be instantiated to represent a given set of information.

This section specifies the template assigning_reference_data.

NOTE  An explanation of a template and the associated instantiation path is provided in the Template overview section.

Figure 1 —  Attribute values set by the template 'assigning_reference_data'.

Figure 2 —  Graphical representation of the template 'assigning_reference_data'.

Figure 3 —  Instance diagram instantiated by the template example

                  #1=PART('/IGNORE', '/IGNORE', '/IGNORE');
                  #2=IDENTIFICATION_ASSIGNMENT('TYRES-010101', '/IGNORE', '/IGNORE', (#1));
                  #3=EXTERNAL_CLASS_LIBRARY('urn:plcs:rdl:std', '$');
                  #4=EXTERNAL_CLASS('/NULL', 'Part_identification_code', '/IGNORE', #3);
                  #5=CLASSIFICATION_ASSIGNMENT(#4, (#2), '/IGNORE');
              

Figure 4 —  Invocation of template - graphical presentation

This section specifies the template assigning_business_specific_reference_data.

NOTE  An explanation of a template and the associated instantiation path is provided in the Template overview section.

Figure 9 —  Attribute values set by the template 'assigning_business_specific_reference_data'.

Figure 10 —  Graphical representation of the template 'assigning_business_specific_reference_data'.

Figure 11 —  Instance diagram instantiated by the template example

                  #1=PART('/IGNORE', '/IGNORE', '/IGNORE');
                  #2=IDENTIFICATION_ASSIGNMENT('TYRES-010101', '/IGNORE', '/IGNORE', (#1));
                  #3=EXTERNAL_CLASS_LIBRARY('urn:plcs:rdl:my_rdl', '$');
                  #4=EXTERNAL_CLASS('/NULL', 'My_org_part_identification_code', '/IGNORE', #3);
                  #5=CLASSIFICATION_ASSIGNMENT(#4, (#2), '/IGNORE');
                  #6=EXTERNAL_CLASS_LIBRARY('urn:plcs:rdl:std', '$');
                  #7=EXTERNAL_CLASS('/NULL', 'Part_identification_code', '/IGNORE', #6);
                  #8=SUBSET('/IGNORE', 'Specialization', '/IGNORE', #4, #7);;
              

Figure 12 —  Invocation of template - graphical presentation

Related capabilities

This capability "Applying classification through the use of reference data" is related to the following capabilities:

• C093: assigning_codes

Related standards

Other ISO standards that defines classes that can be used in information exchanges are:

• ISO 15926 Process Plants including Oil and Gas facilities life-cycle data;
• ISO 13584 Parts Libary.

ISO 15926 Process Plants including Oil and Gas facilities life-cycle data

ISO 15926 includes standardization of the data associated with the engineering construction and operation of oil and gas production facilities. The scope of activities to be supported by this standard includes:

• conceptual process design;
• conceptual engineering design;
• detailed process design;
• detailed engineering design;
• fabrication and construction;
• operations and maintenance.

For more information visit Official ISO TC184/SC4 Web Site(http://www.tc184-sc4.org).

ISO 13584 Parts Libary

ISO 13584 is a series of International Standards for the computer-sensible representation and exchange of part library data. The objective is to provide a mechanism capable of transferring parts library data, independent of any application which is using a parts library data system. The nature of this description makes it suitable not only for the exchange of files containing parts, but also as a basis for implementing and sharing databases of parts library data.

For more information visit Official ISO TC184/SC4 Web Site(http://www.tc184-sc4.org).

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