Information Technology Reference
In-Depth Information
Client
Application programs
VBL
API
Server
Schema
manager
SQL
DML driver
DDL driver
Schema manager
types
optimize
evaluate
Table manager
Indexer
Data file manager
Index manager
File system
F
IGURE
1.3.
Systemarchitecture, showing therelationship between the major
components. Each componentisan independent process. Note thelack of a
single interface to thefilesystem.
Fig. 11.9
Too much clutter. A carefully constructed figure, but flawed. The font is too small and
the lines are too light. The overall structure (the division into four major components) is probably
the most interesting feature, but other details are more highly emphasized. Some of the internal
detail should be omitted. The arrows add little information, and should point both ways, because
information flows out as well as in
Diagrams illustrating system structure often seem to be poor. In too many of these
pictures the symbolism is inconsistent: boxes have different meanings in different
places, lines represent both control flow and data flow, objects of primary interest
are not distinguished from minor components, and so on. Unnecessary elements
are included, such as cheesy clip-art or computer components that are irrelevant
to the system. A poor structural diagram is shown in Fig.
11.11
, with a revision in
Fig.
11.12
.
Another form of diagram is an image, such as a photograph or screenshot. Pho-
tographs are rare in computing papers and, sadly, are often not presented at a high
standard. If you do need to include a photograph, ensure that it will render well in
