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Formalisms in FrameKit

To deal with graphical representations FrameKit distinguishes two notions, formalism and model:

  • A formalism describes a representation rules of a knowledge domain;
  • A model is an instance of formalism. It is one representation expressed using the related formalisms.

Formalisms have to goals in FrameKit. First, they describe a graphical representation. This is done by means of configuration files that enable the creation of new formalism without having to recompile Macao. Second, they are a way to type services in FrameKit.

Description of a Formalism

In FrameKit, description of formalisms is object-oriented. This allows an easy management and updating of formalisms. Each class in the formalism is either a node or an edge (interconnecting nodes) and contains a set of labels (string values, digits...) that characterizes instances of the object. Additional information (how it looks, is it a link to a «sub-level» when the formalism is hierarchic, etc.) must also be provided to fully describe the formalism.

Figure 1: Description of a formalism

Figure 1 shows components of a formalism. A simple formalism dedicated to the description of a local network is defined. It has three classes: two nodes («computer» and «hub») and one edge («link»). To fully describe the formalism, each node or edge must be declared. Each declaration defines the class name, the class apearance and the class information (string(s) associated to any instance of the class). A model corresponding to this formalism is detailed in the model section.

The description of a formalism is stored in a formalism file. Formalism files are used by Macao to dynamically build a "tool palette" from which the user will drag new instances of classes (nodes or edges).

Figure 2: example of Macao screen.

Figure 2 shows a maco screen. The window "untittled.root.1" (botom left) is the one of the model you can create. On top of it, you have a tool palette build for a Petri net formalism (window "AMI-Net"). The "Escher cube" object, in window "untittled.root.1" own all the global information of the model (like its name, author, version...), such information is considered as global.

Hierarchical Formalisms

Macao, and thus FrameKit, are able to handle hierarchical graphical representation. In that case, the formalism is made of several "sub-formalisms". It is thus described by means of several formalism files, each one represents the set of objects that can be found in the corresponding submodel. Thus, hierarchical models are divided into pages.

Let us consider the LOCNET formalism that describes a local network composed with Macintosh computers and Sun workstations (Figure 3). This formalism may consider two global labels : name of the network and its local address. Two nodes are considered, the first one represents a macintosh computer and the other a sun workstation. Finally, three edges may link nodes together: appletalk_link connect two macintosh nodes, ethernet_local_link connect two sun workstation nodes and mixed_link connect one macintosh to one sun.

Figure 3: The LOCNET formalism.

We can use the LOCNET formalism to build a hierarchical formalism called NET, describing a bigger network composed of LOCNET-like subnetworks (Figure 4). Its global labels are the name of the network and its IP address entry. Nodes are:

  • subnet, wich is a link to a submodel having the LOCNET formalism. When doubleclicking on a subnet node, Macao opens a new window to which a LOCNET tool palette is associated. Such nodes are called «boxes»;
  • sun, this node is similar to the one defined in the LOCNET formalism.

One edge, ethernet_link, allows to connect subnets and sun workstation as well. The couple of formalisms ( NET, LOCNET) describe a hierarchical formalism. recursivity is possible: node N in formalism F may point to a submodel having formalism F as well.

Figure 4: The LOCNET formalism.

A NET model is presented in the model section.