Objects, Data And More (OpenACS)

OACS Objects, Data & More
Develop functional specification
Determine inputs, outputs & interaction
Design object model & data model
Design user interaction
Build programming API
Build application pages
templating system
etp applications

Determine inputs, outputs & interaction
what do we need to take in & store
this gives us our fields
what do we need to extract & present
this gives us our structure
BUT - we are not developing a standalone application - our application uses services from the OACS framework
we interact in the object model and with the API interfaces

OACS Objects
How do we decide what should be an object and what can be plain DBMS tables?
“ objects are anything represented in the application's data model that will need to be managed by any central service in OpenACS 4.5, or that may be reusable in the context of future applications”
acs_objects object_id object_type context_id security_inherit_p creation_user creation_date creation_ip last_modified modifying_user modifying_ip tree_sortkey

OACS Objects
What do we get for this effort?
Permissions (the killer benefit)
General Comments
Content Management
etc.

Where might we NOT define objects?
We might have internal table-based data that does not directly interact with other parts of the system
eg. exchage rates
We either specifically don’t want them to be available, or if we do we should be exposing them through method calls

Defining OACS Object Types
object type for Lecturers
inherit from the person object type
add storage for: faculty, department & office
We need to register the new type in acs_object_types
acs_attributes anyone?
create function inline_0 () returns integer as ' begin PERFORM acs_object_type__create_type ( ’’ lecturer'', -- object_type '’Lecturer'', -- pretty_name '’Lecturers'', -- pretty_plural '’person’' -- supertype '’lecturerss'', -- table_name '’lecturer_id'' -- id_column null, -- package_name ''f'', -- abstract_p null, -- type_extension_table '’lecturer.name'' -- name_method ); return 0; end;' language 'plpgsql'; select inline_0 (); drop function inline_0 ();

Creating the objects
Even though we think of our “lecturer object” in OO concepts, it is ultimately stored in a regular relational database table
We hide this by creating stored functions that act as creators, destructors and accessors

So where do we put all this sql? packages notes … lecturers sql oracle … postgresql lecturers-create.sql lecturers-drop.sql

And what are all these .xql files? Let’s say we have the following files: index.tcl index.xql index-oracle.xql index-postgresql.xql First Second Last

What should go in each file?
can the sql be expressed in SQL92?
index.xql
is custom code required for a particular dbms?
index-dbms.xql
What about inside the tcl file?

.xql file format <?xml version="1.0"?> <queryset> <rdbms><type>postgresql</type><version>7.1</version></rdbms> <fullquery name="get_date"> <querytext> select to_char(creation_date, 'DD/MM/YYYY') from acs_objects where object_id = :response_id </querytext> </fullquery> </queryset> Rdbms line not used In the default .xql file

How do I use the xql files?
set date [ db_string get_date {} -default 0 ]
This is where sql could go. It’s convenient for you … not convenient for someone trying to port your code to another rdbms

I changed sql in the tcl file and nothing happened!
Look out - many packages have sql inside the tcl db_ function call, but it is overidden by the relevant .xql file

I changed sql in the .xql file and nothing happened!
Once the .xql file is loaded once by the query processor, it is cached in the server
This is good for performance
But bad for development
You need to go to the package manager (acs-admin/apm), click on your package, click on manage files, and set your .xql file to be watched

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Objects, Data And More (OpenACS)

by Mark Aufflick on Sep 29, 2007

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