工业自动化系统和集成.产品数据表示和交换.第108部分:集成应用资源:显示几何产品模件用参数化和约束条件

[中文适用范围]： ISO 10303 的这一部分指定了用于表示模型参数和约束的资源构造，以及将它们与传输模型的几何或其他元素相关联所需的机制。 这些功能的使用可能允许模型在其原始系统中的行为的某些方面与基本模型本身一起传达。 传输此附加信息的目的是向接收系统提供数据，使其能够在传输后的模型中重建相应的行为特征。 理想情况下，这将使模型能够在接收系统中进行编辑，就像模型是在接收系统中创建的一样。 如果不交换所谓的设计意图信息，这是不可能的。 ISO 10303 的这一部分能够捕获和传输设计意图的一个重要方面。 第 4 条定义了将模型参数与模型中的各个量关联起来的方法，以提供尺寸值和其他变量属性的编辑。 第 5 条规定了根据模型参数之间的数学关系对约束关系进行建模。 这些约束不仅限于产品形状的建模；它们被设计为适用于任何可能有助于捕获和传输数学指定关系的情况。 第 5 条还定义了一类描述性（非数学）约束。 第 6 条定义了变体表示，包含模型以及所有相关参数和约束，这些参数和约束可能有助于传输后的有效编辑。 第 7 章定义了一组显式几何约束的专门表示，这些约束专门适用于边界表示和密切相关类型的形状模型的元素。 这些是第 5 节中指定的描述性约束的子类型。 最后，第 8 节提供了二维草图的表示，这构成了 CAD 建模中许多形状构造方法的基础。 草图是前面条款中定义的参数化和约束信息的重要应用领域。 该模式中提供的功能也可以用作参数化绘图表示的基础。 以下内容属于 ISO 10303 本部分的范围： ——通过变量与其中出现的量的关联来对模型进行参数化； ——定义参数之间数学关系的约束； ——对模型的约束表示为它们的组成元素或这些元素的属性之间的关系； ——将参数和约束与表示级别的模型关联起来，以创建产品、计划、过程或组织的变分模型； [外文原描述]： ISO 10303-108:2005 specifies the resource constructs for the representation of model parameters and constraints in CAD or other kinds of models, together with the mechanisms necessary for associating them with geometric or other elements of transferred models. The use of these capabilities potentially allows certain aspects of the behaviour of a model in its originating system to be conveyed together with the basic model itself. The intention in transferring this additional information is to provide the receiving system with data that will enable it to reconstruct corresponding behavioural characteristics in the model following the transfer. Ideally, this will enable the model to be edited in the receiving system just as as though it had been created there. That would not be possible without the exchange of what is known as design intent information. ISO 10303-108:2005 enables the capture and transfer of an important aspect of design intent. The following are within the scope of ISO 10303-108:2005: parameterization of models through the association of variables with quantities occurring in them, including dimensional values; constraints defining mathematical relationships between variable parameters; constraints on models expressed as descriptive relationships between their constituent elements or attributes of those elements; specialized descriptive constraints corresponding to the geometric constraints commonly used in product shape modelling (e.g., parallelism or tangency between geometric elements); applications of parameterization and constraints to two- and three-dimensional shape models; specialized representations for two-dimensional geometric sketches or profiles; representation of models that are incompletely defined in the sense that certain values in the model may be regarded as not fully constrained. The following are outside the scope of ISO 10303-108:2005: procedural or history-based model representations, expressed in terms of sequences of constructional operations; implicit or procedurally defined constraints, inherent in the operation of constructional operations; solution methods for systems of constraint equations; form features of shape models; behaviour of a system in which a variational model is edited following a transfer; considerations of accuracy in constraint satisfaction. The following notes apply to the excluded capabilities. Procedural or history-based representations are the subject of ISO 10303-55. Methods of solving constraint equations are the responsibility of the application systems involved in the exchange. ISO 10303-108:2005 merely transfers the constraint relationships that need to be solved. Various other parts of ISO 10303 provide representations for different application-oriented views of form features. The information transmitted by the use of ISO 10303-108:2005 is intended to allow implementers to provide 'reasonable' or 'intuitive' behaviour by receiving systems following the transfer of a model in the circumstances mentioned above, but ISO 10303-108:2005 does not prescribe the detailed nature of such behaviour or of its presentation to the system user. Accuracy considerations are essentially the same in the ISO 10303-108:2005 context as those arising generally in the geometric modelling of product shape. Means are provided elsewhere in ISO 10303 for addressing accuracy issues.