MODEL semantic relationships

To achieve these consistencies, MODEL.LA. provides a series of semantic relationships among its modeling elements, which are defined at different levels of abstraction. For example, the semantic relationship (see 21 1), is-disaggregated-in, triggers the generation of a series of relationships between the abstract entity (e.g., overall plant) and the entities (e.g., process sections) that it was decomposed to. The relationships establish the requisite consistency in the (1) topological structure and (2) the state (variables, terms, constraints) of the systems. For more detailed discussion on how MODEL.LA. maintains consistency among the various hierarchical descriptions of a plant, the reader should consult 21 1. 

Catalysis models have clear semantic relationships to one another. At any level of abstraction, they form an important part of the inspection criteria for those models. Across levels of refinement, these rules, together with the rules for refinement, provide a concrete basis for design reviews. 

If the modeling elements of LCR represent the modes of a network, the semantic relationships constitute the links (edges) of the network. There... 

The first two semantic relationships establish the structure of a modeling element they allow the declaration of the attributes and methods of a modeling element. Although all object-oriented systems possess, by definition, the first two semantic relationships and no special computer-aided provisions are needed, they have been included here for completeness. 

The following two semantic relationships establish the links between a basic modeling element and its derivative subclasses of modeling objects and instances. Both of them are isomorphic mappings. 

Specification mappings, described by the following sbc semantic relationships, are used to specify the value of attributes of various modeling elements. They express, (a) binary relations, such as whole/ part links, (b) communication lines among modeling objects, or (c) the value of simple describing properties. 

The is-attached-to semantic relationship establishes linkages between different modeling elements, allowing flow of information from one to the otherfs). Furthermore, since atoms know their membership into various functional groups, auxiliary links are automatically established thus LCR creates automatically the following semantic connection ... 

The addition of descriptive attributes and methods to each of these new modeling classes further characterizes each class. To characterize the modeling class excited-state-effects, we add attributes and methods descriptive of singled (S) and triplet (T) states. The states are refined further by energy level. For example ground states (S(,To) are differentiated from their excited states (S,T,) as well as from their higher states (S2,T2, and S3,T3). As before, we link these attributes using the semantic relationship is-attribute-of ... 

We initiate the development of covalent-bond by creating the modeling element and establishing the normal superclass links using the semantic relationship, is-a (Fig. 9) ... 

We can also specialize these methods according to physical requirements and chemical requirements. This provides an abstraction barrier between what is true (i.e., the physical laws) and what is believed to be true (i.e., current theory). For example, suppose that the methods favor-able-interatomic-distance-p and potentially-stable-bond-formation-p are physical requirements whereas the methods available-bonding-electron-p and proper-orbital-symmetry-p are chemical requirements. We represent this to covalent-bond by associating the top-level methods (i.e., methods associated with K j ), chemical requirements, and physical requirements, to covalent-bond directly (i.e., we override the method inherited by the mother model class). This is accomplished using the semantic relationship is-method-of, as was demonstrated earlier ... 

To demonstrate the utility of LCR and the interaction between various modeling elements, semantic relationships, and supporting methods, let us first consider the pyrolysis of ethane forming principally ethylene and hydrogen. Although this example is relatively simple, it highlights the functionality of LCR and underscores various issues that require resolution for computer implementation to be successful. 

MODEL.LA. possesses the same set of 13 semantic relationships as LCR, with the same semantic implications ... 

Semantic-Relationship 5 is-composed-of. Relates a modeling object to its component parts ... 

Semantic-Relationship 11 is-characterized-as. It is used to specialize a modeling class by specifying a fixed, default value for a given attribute of the class for example, the following statement... 

Semantic-Relationship 12 is-disaggregated-in. As in LCR, this semantic relationship associates a modeling element, located in a given context, with its constituent modeling components that are located at a different (more detailed) context. For example,... 

MODEL.LA. is a language with infinite extensibility of its vocabulary, enabled by a fixed set of she modeling hierarchies and a fixed set of 13 semantic relationships. In Section IV.C, we discussed the hierarchies of modeling subclasses emanating from the six basic modeling elements. What is far more important for the modeling power of MODEL.LA. is its... 

Consider again the overall process of Fig. la. It can be represented by an instance of the modeling element, generic-unit (or, plant, if we want to take advantage of its special attributes). MODEL.LA. can derive automatically the necessary modeling instances for the refined plant of Fig. lb, through the invocation of the following semantic relationship ... 

Semantic relationships provide links between the various modeling elements, described above, and give rise to a network known as semantic... 

A modeling language is needed to provide multi-faceted representation of the evolving design artifact, and represent the design tasks and their semantic relationships. 

In a similar manner, the semantic relationships among the various modeling objects of MODEL.LA. allow the transfer of information among these objects. When used together, LCR and MODEL.LA. allow functional and topological information derived at one point of the process to be accessible from any other point in the process. 

Notice the interplay between the methodology and the specialized modeling languages and the importance of that interplay. These languages enable the methodological approach. For example, find-all-pathways applied to a chemical species set (CSS) utilizes the semantic relationships of LCR to construct the potential-reaction-list. Similarly, the representation utilized by LCR allows enabling-criteria to be explicitly associated with each reaction these criteria can come from the state representation... 

Although the knowledge required to assess the potential for the prevention or dissipation of hazards is often held by different abstractions of the overall representation, the semantic relationships of the modeling languages afford efficient access to this information. The effect of protective processes, equipment restraints, sensors and control systems, emergency procedures, etc., are captured as constraints. Constraints may be embedded in the underlying representation as equations, or be associated directly to it via a constraint list, i.e., a collection of explicit process restraints. These restraints may be passive, such as materials of construction, or... 

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