This part of ISO 10303 specifies resource constructs for the representation of models of the procedural or construction history type, defined in terms of the sequence of constructional operations used to build them. Representations of the operations themselves are not specified here; the mechanisms provided in this document allow the use of entity data types defined in other parts of ISO 10303 for that purpose (see clause 4.2.5). The following are within the scope of this part of ISO 10303: — The specification of sequences of constructional operations for the generation of any kind of explicit representation or model; — The hierarchical structuring of constructional sequences; — The embedding of explicitly defined elements in constructional sequences for the representation of hybrid models; — The use of representation_item definitions from other parts of ISO 10303 to represent construc-tional operations for instances of those representation, items; — The definition of a dual representation by association of a procedural model with an explicit 'cur-rent result' model, the latter acting as a representative example of the parametric family of models defined by the former; — The association of design rationale information with a procedural model; — The identification, in a procedural model, of explicit elements selected by interactive picking from the visual display of the model in the sending system; — The identification, in a procedural model, of constructional operations that can be suppressed for purposes of model simplification; — Specialization of the foregoing capabilities for the procedural representation of shape models. The following are outside the scope of this part of ISO 10303 : — Any mechanism for the 'persistent naming' of elements of an explicit model based on details of the procedural sequence used to create them; — 'Macro' capabilities requiring the use of control structures such as if... then... else or repeat... until. Such structures are defined in ISO 10303-11 for use in local and global rules, but no analogous facilities are provided in this document to allow conditional operations in procedural models.