I'm trying to follow the directions to recreate the diagram in Lab 4, slide 24
In the model notes there is a textual constraint:
For each Project: existing completionDate >= startDate
I believe startDate and completionDate are supposed to be role names. in the PPT, these are shown as bracketed blue text by the respective FactTypes. I ...
thanks Brian, your explanation regarding role sequences clarifies the matter. maybe one day the constraint should be re-named 'sequence constraint'
for anyone who might be interested in the exercise left to the reader on the last page of Lab 4,
I did the following tests.
Thing is a real thing
Thing is a tangible thing
The name 'equality constraint' may be misleading. You might think that it's some form of test for equality of values. What the constraint really enforces is a constraint on which roles, or role sequences must be played by an object, if that object participates in a role or role sequence in a different fact type. For example, if you had a ...
I am developing extensions for an existing commercial sql server database and application.
I have to model the existing schema and create a separate model for the extension that refers to the objects in the existing schema.
I don't want to regenerate or alter the existing schema, so all the constraints pertaining to the whole system must be ...
re: Lab4 pg 24
LanguageVersion is of Language(name)
LanguageVersion has VersionNr
from the diagram in the ppt, I'm having trouble understanding what is the intended outcome of the equality constraint for
|is of| |
|has | |
Every permutation I try has a reading that kind of ...
Thanks, referring to slide 20 notes again:
I'm sorry to be a pest about it. I've tried to follow this to the exact detail and no matter how I try, absolutely nothing happens.
For clarity's sake, ''the first Fact type'' I understand to mean the binary fact type glyph above its reading 'is allergic to' but I don't understand why you said ...
I think it may read better in the following way:
1) Select Internal Uniqueness constraint in the Toolbox.
2) Click the first Fact type on the drawing surface. The constraint will be displayed but grayed out because we need to specify what roles this constraint covers.
3) Click the first role, then the next. When all ...
In particular, there is a rather serious pitfall on slide 7, which I have annotated as follows:
*Note: when entering a fact type in the fact editor, do not type an intervening space between object and identifier type in the fact
Patient(nr) has PatientName()
Entering a space between entity type 'Patient' and identifier '(nr)' causes the ...
On slide 34 of Lab1, the third step does not happen as described. Perhaps I did not understand what the ''document tab'' is, or the slide has become outdated. What did work is:
Instead of step 3: After completing step 2, a Relational View button is automatically created. Simply clicking this shows the relational view page.
I am collecting my ...
Thanks. The Lab ppt's are really nice.
I have a minor question about pg 20 of lab1, which reads in the notes:
The toolbox gesture for this is:
1)Select Internal Uniqueness Constraint
2)Click the fact to add it to. The constraint will be added activated with no constraints.
3)Click the first role
4)Double click the second role to add ...