Interaction between objects

Catalysis treats collaborations as first-class units of design work. This is because we take seriously the maxim that decisions about the interactions between objects are the key to good decoupled design. Collaborations can be generalized and applied in many contexts. 

Objects that have similar behaviors are members of the same type they satisfy the specification of that type. Behaviors are specified in terms of attributes that are a valid abstract model, called a type model, of many possible implementations. Each action is described in terms of its effect on the attributes of the participating objects and the outputs it produces. The most interesting aspects of a design are the interactions between objects. You can abstract away detailed interaction protocols between objects by using joint actions and collaborations and you can describe specific interactions as refinements of a more abstract description. 

Each individual state chart effectively specifies how every action on the primary type affects that one specification type. In contrast, a complete action specification defines how one action on the primary type affects any specification type member. The composition of all change dates transitions, on ary and all specification types, constitutes change dates operation specification for the scheduler. Do not confuse this state chart view with internal design, when we will actually decide internal interactions between objects within the scheduler, the primary types whose behavior we describe will be these internal objects. 

In Chapter 4 we deal with the interactions between objects—both inside the object we have specified (as part of its implementation) and between our object and others—to understand how it is used by our (software or human) clients. 

We have seen how an entire sequence of interactions between objects can be abstracted and described as a single joint action. We will next see how even in program code, an operation invocation itself has two sides the sender and the receiver. By using input and output parameters, a localized operation specification decouples the effect on the receiver from any information about the initiator. 

Actions and operations describe interactions between objects an effect describes state transitions. You use effects to factor a specification or to describe important transitions before the actual units of interaction are known. Just as attributes are introduced when convenient to simplify the specification of an operation, independent of data storage, so can effects be introduced to simplify or defer the specification of operations. 

Action Describes a complex protocol of interaction between objects as a single action, again characterized by the effect it has on the participants. What sequences of detailed actions will realize the effect of the abstract action Use state charts, sequence or activity diagrams. 

The same diagrams can be used to show the interactions between objects in the business world and interactions between large components. 

Much of the notation is useful throughout different stages of the process. For example, we use the same tools to describe the interactions between people and a machine we propose to build, to describe the interactions between objects collaborating inside the machine once designed, and to describe business tasks and processes. For this reason, many of the notational tools are introduced early in the case study and are then reapplied in each phase. 

Some business models focus on the types that a single client can manipulate, such as the Drawing example here. In this case, all the actions are shown localized in the Drawing and its constituents. Other models must be more concerned with interactions between objects, such as the Library example. Figure 14.1 illustrates both models. 

A collaboration diagram defines interactions between objects. A collaboration is a set of actions that are related in some way, usually a common goal. Here are some examples. 

This chapter describes experimental and conceptual issues in mesoscale self-assembly (MESA), using examples from our work in the assembly of millimeter- and micron(micrometer)-sized polyhedral objects using capillary forces. In MESA, objects (from nm to mm in size) self-assemble into ordered arrays through noncovalent forces. Three systems that use capillary forces in MESA are described these involve the assembly of objects into two-dimensional arrays at the perfluorodecalin/H20 interface, into three-dimensional arrays at curved liquid/liquid interfaces, and into three-dimensional arrays from a suspension in water. The capillary interactions between objects can be viewed as a type of bond that is analogous to chemical bonds that act between atoms and molecules. 

We will describe two mesoscale, self-assembling systems in which the interactions between objects are based on capillary forces. The first is based on polyhedral polydimethylsiloxane (PDMS) objects at a perfluorodecalin (PFD)/H20 interface. These objects have their faces patterned to be either hydrophobic or hydrophilic, and they assemble via lateral capillary forces that originate from interactions between these faces (Fig. 4. la). The second system uses polyhedral objects that are suspended in water and have selected faces covered with a water-insoluble liquid - either a hydrophobic organic liquid or a liquid metal solder these objects assemble via capillary forces into three-dimensional (3D) structures (Fig. 4.1b). 

By definition, any interaction between objects that tends to hold them together is a bond. In our work, capillary interactions provide the bond between objects. In general, a bond between two molecules or objects has two components one attractive, and one repulsive (Fig. 4.3). At some distance, these forces are equal... 

Objects with an asymmetric distribution of hydrophobic faces have a corresponding asymmetric distribution of vertical capillary forces that causes these objects to tilt at the interface (Fig. 4.7). This tilt shapes the contours of the menisci, because the meniscus on a tilted face is not symmetric about the center of the face. Two faces on different plates are held together more strongly when the contours of their menisci match than when they do not match. Thus, tilting can regulate the strength of attractive interactions between objects. 

Bohr deduced the correspondence principle A quantum description of atoms must tend to the classical description for larger dimensions. He also deduced the complementarity principle There are interactions between objects and the instruments used to observe them. Using the complementarity principle he concluded that there is always a limit to the abihty of scientists to observe (and to know) atoms. With this concept he acquired an influence beyond the world of physics. 

Rather than having a language whose purpose is to run a machine the language should naturally describe what objects there are and what actions they are taking. Objects are inherently distributed and their interactions asynchronous with real time, event-driven behavior. This implies that one could define a system and its own definition would have the necessary behaviors to characterize natural behavior in terms of real time execution semantics. Application developers would no longer need to explicitly define schedules of when events were to occur. Events would instead occur when objects interact with other objects. By describing the interactions between objects the schedule of events is inherently defined. 

The interactions between objects and polymers, etc. are ill-understood. Assuming that the object is the primary concern of the conservator, consoli-dants, adhesives and coatings should be applied only when necessary to the survival of the object. They should not be used as an alternative to proper packaging, environmental control, etc. Given the difficulties of removing polymers, they should be applied sparingly. 

As these systems do not change symmetry, a system can therefore be considered to be composed of either a mixture of protons, neutrons and electrons, or a mixtme of atoms with the same symmetry, or an enserttble of molecules still with the same symmetry, or a group of molecules with the same symmetry. The ensemble of objects that corresponds to the minimum interactions between objects is always chosen. 

For a simultaneous visualization of variables and objects within the new coordinate system, biplots can be used. In these, objects and variables are scaled with the variance described by the corresponding principal component. Variables around the origin have only a small influence on the plotted principal component, while interactions between objects and variables are indicated through their distance and angle. 

The Mosaic system, developed by Jean-Marie Adrien at the University of Paris VI, is a typical example of a tool for implementing modal synthesis (Adrien, 1991). It provides a number of ready-made substructures such as strings, air columns, metal plates and membranes, as well as substructures for the simulation of actions such as bowing and hammering. Instruments are thus programmed by networking these substructures. In Mosaic terms, substructures are called objects and the interactions between objects are referred to as connections. A connection between two objects also acts as an interface between the user and the instrument for example, the connection between a bow and string provides the means for user-customisation of the parameters that drive the interaction, such as pressure, speed, etc. 

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