8.2.5 Representations

The XML files exported from MetaEdit+ will also contain the graph representations and their elements. It is not necessary to include these in files produced by other programs, but they can be included if desired. If you do not include them, opening the graphs will create a layout, which you can improve using the editor’s commands, e.g. Graph | Layout... in the Diagram Editor.

The representation data is in the http://www.metacase.com/gxlGOPRRRepr namespace, with a main element for each type of representation: diagram, matrix and table. All representations share a mandatory attribute for the timeStamp, in xsd:dateTime format (or as an empty string to use the time of import), and an element pointing to their graph (always as an href reference, since the graph will have already been defined). They will contain elements for the representations of conceptual objects etc., and each of these will refer to its conceptual object with an object element – once again using href. Note that the tags for these references to conceptual data will be back in the standard namespace, http://www.metacase.com/gxlGOPRR, so will have to declare that with an xmlns= attribute.

Diagram

The start of a diagram looks like this:

<diagram 
  displayGrid="false"
  grid="10,10"
  timeStamp="2000-12-19T11:26:40.000Z"
  useGrid="true"
  xmlns="http://www.metacase.com/gxlGOPRRRepr">
    <graph
      href="#_22_792"
      xmlns="http://www.metacase.com/gxlGOPRR">
    </graph>

An object representation specifies its position and scale as x,y pairs. (The numbers are represented in the same way as a single literal number in MERL math..evaluate: see Section 6.5.6.)

<objectRepr id="_22_829" place="150,220" scale="1,1">
    <object
      href="#_22_4854"
      xmlns="http://www.metacase.com/gxlGOPRR">
    </object>
</objectRepr>

Relationships and roles are specified as part of a binding representation. This points directly to its conceptual binding and its object representations, and indirectly via its connection representations’ ids to its connections and their roles. The position and scale of the relationship symbol are included as attributes in the bindingRepr tag, along with an attribute specifying whether the relationship is binary and straight.

<bindingRepr
  isStraight="true"
  place="179,160"
  scale="1,1">
    <binding
      href="#_22_827"
      xmlns="http://www.metacase.com/gxlGOPRR">
    </binding>
    <connectionRepr id="1">
        <objectRepr href="#_22_830"></objectRepr>
    </connectionRepr>
    <connectionRepr id="2">
        <objectRepr href="#_22_829"></objectRepr>
    </connectionRepr>
</bindingRepr>

A connectionRepr can also specify the breakpoints along its line, starting from its object, and any manual offset of its target point, i.e. where it intersects its object. Points are expressed as x and y co-ordinates separated by a comma; the points themselves are separated by a single space.

<connectionRepr
  breakpoints="100,170 140,150"
  id="2"
  objTargetOffset="-3,-27">

Matrix

A large amount of the information for a matrix is at the level of the matrix itself, expressing the layout choices made in the Matrix Editor toolbar or menu bar.

<matrix
  axisDisplayMode="axesDisplayText"
  bindSelect="secondRole"
  cellDisplayMode="displayText"
  displayStringSelector="userPrintString"
  rowLabelsWidth="86"
  showFirst="false"
  textStyleSymbol="default"
  timeStamp="2006-11-14T14:00:52.781Z"
  xmlns="http://www.metacase.com/gxlGOPRRRepr">
    <graph
      href="#_22_792"
      xmlns="http://www.metacase.com/gxlGOPRR">
    </graph>

The display modes for the axes and cells end in Text, TextAndSymbol or Symbol, corresponding to the choice in the Axis and Cell menus. The choice in the View menu is shown in the bindSelect attribute’s value, with Row Role represented as firstRole, Column Role as secondRole, and Relationship as relationship. The View | Directed? choice is represented in the showFirst attribute. Finally, the displayStringSelector value is taken from Cell | Text Display..., with values of userPrintStringWithType, userPrintString, typeName, letter, and justX corresponding to the choices in the dialog shown by that command.

The axis elements are represented by tags specifying on which axis the object is, hAxis or vAxis, how wide the element is (a negative value for a column renders it hidden), and which object it represents:

<hAxis width="45">
    <object
      href="#_22_4673"
      xmlns="http://www.metacase.com/gxlGOPRR">
    </object>
</hAxis>

Relationships and roles are not directly stored in a matrix, so are not represented in the XML: their presence is calculated from the conceptual graph information, and their display format taken from the attributes of the matrix tag.

Table

The table specifies its font and object type in attributes, along with an export-only objectTypeName, ignored on import, that shows the user-visible name of the object type. It specifies either one width element, for the width of all columns, or a separate width element for each column.

<table
  font="default"
  objectType="Object_AppState_sysadmin_3150526244"
  objectTypeName="State [Watch]"
  timeStamp="2006-11-14T14:45:49.871Z"
  xmlns="http://www.metacase.com/gxlGOPRRRepr">
    <width>100</width>
    <graph
      href="#_22_792"
      xmlns="http://www.metacase.com/gxlGOPRR">
    </graph>

Table elements are listed in order. They have no information of their own, but simply point to their conceptual object:

<tableElt>
    <object
      href="#_22_3617"
      xmlns="http://www.metacase.com/gxlGOPRR">
    </object>
</tableElt>