International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXX V, Part B2. Istanbul 2004
knowledge to be able to interpret the appropriate meaning of an
object(Bishr, 1998). This is known as data/knowledge packets that
allow both knowledge and data to be represented in a unified
model (Doyle and Kerschberg, 1991). A data/knowledge packet
could look like this
{
ChangeClass C
ObjectSetb
ObjectSeta
Rules! IF—THEN expression
1
f
A object set can contains n objects (n>=0), firstly we classify
change by comparison the cardinality of ObjectSetb and
ObjectSeta there are 6 types of change: 0 to 1 (there is zero object
in ObjectSetb, there is only one object in ObjectSeta); 1 to 0; 1 to
l; 1ton;nto 1; n to m.
The first three types of changes influence single geographical
feature, the other influence several geographical features. We
classify the spatio-temporal changes based on the following
aspects:
1)Levels of change
Object
Object component
Component attribute
2) factors related to change
Object set and its attributes
Object
The relationship of objects in set
Object components and their attributes
3) Only focus on single change
4) change impact on simple object.
Change has three levels, i.e. change about object, change about
object component, change about component attribute. For
example, disappearance is the object change, distortion is change
about object component and component attribute. We take into
account four factors that are used to identify changes, they have
hierarchy relationship, object set contains object, object is
composed of components, and component is described by
attributes. By these hierarchy factors, we can shorten the
identifying process of changes. For example , if we identify the
disappearance of an object, it is dispensable to judge whether the
shape of the object changed. Here, we only focus on the changes
affecting simple objects not include changes affecting complex
objects. We only define the single change and not consider the
multiple changes. For example, an object changes its shape, its
area may change. We can determine the object has two types of
change, distortion and area change. We don’t make up a complex
change by the two simple changes.
4.3 Classification and Representation of changes impact on a
single object
We regard object set, attributes of object set, object, object
component and attributes of components as the factors to identify
spatio-temporal changes. By comparing the value before change
and that of after change of the same factor, we give the taxonomy
of the spatio-temporal changes impact on a single geographical
object. There are many expressions used in the description of
changes(as show in table 1). Here, we detailedly explain the
function of semantic component of a geographical object. Given a
scenario of the change of a geographical object, if the value of the
semantic component of the object has not changed, we can
announce the object is the same object.
Table 1 expression and their meanings
Now , we use the data/knowledge packets to describe changes.
Table 2 gives the taxonomy of spatio-temporal changes related
to a single geographical object. The taxonomy has hierarchy.
These changes are basic. In the real world, a geographical feature
may have several changes at the same time. By combining these
basic changes, we can model scenarios of the real world changes.
600
Expression meanings Expression meanings
ObjectSet Object Set Position(OO) Position
ONum(Object | Cardinality Direction(OO) Direction
Set) of set
O Geographic GType(OG) Geometry
al object type
Os Semantic Length(OG) Length of
component line object
OO Orientation Area(OG) Area of
component area object
OG Geometric | Numltems(OA) | Number of
component attributes
OA Thematic ItemVal(OA;) Value of
component attribute A;
OR Topology Xp The state
component before
change
oT Temporal X, The state
component after
change |
Inter.
Chz
44 C
many
Many «
have it
p
Nani
cha
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