Since much of the material that follows deals with structures and how they behave when data is loaded into them, a brief introduction to the relationship between data and display is germane. Data entry is treated carefully in Appendix 3 and you will want to read this if you are not already familiar with the process.
What follows specifically concerns ACEDB text windows rather than the specialized graphical displays for maps and sequences.
Consider the following description of a t-shirt designated "sam1" as read in via an .ace file:
TShirt : sam1 Remarks "one of my favorites!" Price : 15.95 Red Damage : "Ripped" "September 12, 1991" Year : 1989 Faded Remarks "graphic offends Paul's mother"Once the data is read into the database, ACEDB displays "sam1" as follows:
In comparing the .ace file contents with the window, note the following:
First, the name of the object, "sam1", appears in the upper left corner of the window as well as in the title bar (where the class name also appears). Second, the overall layout of the the text window--that is, the order in which labels appear from top to bottom--is independent of the data file. Window layout is determined by the model itself; as data is read in, fields are populated on a "first come, first serve" basis. For example, Remarks is below Price in the ?TShirt model, but one of the Remarks precedes the Price in the data.
Third, unused fields are NOT displayed in the window. The display software condenses the outline and shows only the branches and fields that are actually used. This is a very important feature because it means a model definition can be arbitrarily complex without cluttering the data display, and biological data is often "sparse". The unused fields are nonetheless available if new data becomes available. When filled they will be visible as well.
Fourth, if a label is used, the branches leading up to it are always included in the object and are shown to the user. Thus the category labels "Characteristics" and "History" are automatically visible even though they were not mentioned explicitly in the data. The use of a field implies the use of the antecedent labels.
Finally, the single field following the "Remarks" label displays two different entries. The next section discusses this important point.
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