Obix: An Introduction
by Christian Neumanns
www.obix.lu
Welcome!
Agenda
| What is Obix? |
5 min. |
| Why Obix? |
10 min. |
| Simple examples |
30 min. |
| Questions? |
5 min. |
|
+- 50 min. |
What is Obix? (1/3)
- programming language
- compiled
- object-oriented
- statically typed (dynamic typing is possible)
What is Obix? (2/3)
- compiler generates Java binary code (.class files)
- applications run on any system with JVM (e.g. Linux, Mac, Windows, etc)
- Java and Obix code can easily be mixed
- all existing Java software can easily be used in an Obix application
What is Obix? (3/3)
- open source, free software (GPL v3 license)
- free of charge
- currently: alpha version
- one-man project -> open-source community
- for more information: www.obix.lu
Why Obix?
Reliability: why it matters? (1/2)
- Fact #1: It is practically impossible to write error-free software
- Industry average: 1 to 25 bugs in 1000 lines of code for delivered software
- -> not less than 100 to 2500 errors in mid-sized application (100000 lines) delivered to customers
- -> reason all licenses say: "software is without any warranties"
Reliability: why it matters? (2/2)
- Fact #2: Costs to repair programming errors typically increase dramatically (by orders of magnitude!) when they are detected at a late stage
Maintainability: why it matters?
- New bugs are often introduced when a program is modified
- About 70% of the total time is typically used to maintain applications
- Programmers prefer creating new programs over maintaining old ones
Reliability: how to improve?
- more testing
- advantages
- one of the most effective ways to find errors
- provides accurate, error-free and up-to-date documentation
- greatly helps to detect errors when refactoring/maintaining
Unit-testing example
service string_utilities
end
Unit-testing example
service string_utilities
command double_string
end
end
Unit-testing example
service string_utilities
command double_string
in string type:string end
out result type:string end
end
end
Unit-testing example
service string_utilities
command double_string
in string type:string end
out result type:string end
script
o_result = i_string & i_string
end
end
end
Unit-testing example
service string_utilities
command double_string
in string type:string end
out result type:string end
script
o_result = i_string & i_string
end
test
end
end
end
Unit-testing example
service string_utilities
command double_string
in string type:string end
out result type:string end
script
o_result = i_string & i_string
end
test
script
end
end
end
end
Unit-testing example
service string_utilities
command double_string
in string type:string end
out result type:string end
script
o_result = i_string & i_string
end
test
script
test "a" // call command double_string with i_string = "a"
verify v_result =v "aa" // verify result is "aa"
end
end
end
end
Unit-testing example
service string_utilities
command double_string
in string type:string end
out result type:string end
script
o_result = i_string & i_string
end
test
script
test "a" // call command double_string with i_string = "a"
verify v_result =v "aa" // verify result is "aa"
test "YaJUG is great!"
verify result =v "YaJUG is great!YaJUG is great!"
end
end
end
end
Reliability: how to improve?
- more testing
- advantages
- one of the most effective ways to find errors
- provides accurate, error-free and up-to-date documentation
- greatly helps to detect errors when refactoring/maintaining
- drawbacks
- some programmers don't write tests
- requires time and increases costs
- never reveals all errors
Reliability: how to improve?
- 'fail fast' principle supported by the programming language
- To increase the reliability and maintainability, and reduce costs, software errors must be detected and repaired as early as possible.
- Errors should preferably be automatically detected at compile-time, or else as early as possible at run-time.
'Fail fast' rule ignored!
'Fail fast' rule ignored!
...
'Fail fast' rule ignored!
...
coding error:
'Fail fast' rule ignored!
...
coding error:
...
Javascript 'try to continue' example
var product = {
identifier : 123,
description: "banana",
price : 50
}
Javascript 'try to continue' example
var product = {
identifier : 123,
description: "banana",
price : 50
}
alert(product.description) // displays: banana
Javascript 'try to continue' example
var product = {
identifier : 123,
description: "banana",
price : 50
}
alert(product.description) // displays: banana
product.desciption = "apple"
alert(product.description) // displays: banana
Javascript 'try to continue' example
var product = {
identifier : 123,
description: "banana",
price : 50
}
alert(product.description) // displays: banana
product.desciption = "apple"
alert(product.description) // displays: banana
alert(product.desciption) // displays: apple
Javascript 'try to continue' example
var product = {
identifier : 123,
description: "banana",
price : 50
}
alert(product.description) // displays: banana
product.desciption = "apple"
alert(product.description) // displays: banana
alert(product.desciption) // displays: apple
alert(product.foo) // displays: undefined
A simple example
- ERP application with data type 'product':
type product
end type
A simple example
- Obix source code for type 'product':
type product default_factory:yes
attribute identifier type:positive32 end
attribute description type:string end
attribute vendor type:string end
attribute price type:zero_positive32 end
end type
- to create a banana:
var product banana = fa_product.create ( &
identifier = 123 &
description = "banana" &
vendor = "Best fruits" &
price = 50 )
Some conveniences
- code size (increases productivity)
- no code duplication (increases maintainability)
- separation of design and implementation enforced by the language (increases maintainability)
- input assignments eliminate ambiguities (increases maintainability)
var product banana = fa_product.create ( 123, "banana", "apple", 50 )
var product banana = fa_product.create ( &
identifier = 123 &
description = "banana" &
vendor = "apple" &
price = 50 )
Some conveniences
- everything is an object (no primitive types and no arrays)
- distinction between positve32 and zero_positive32 types (increases reliability)
- no 'package' and 'import' statements (increases productivity)
'Fail fast!' support
-
var product banana = fa_product.create ( &
...
price = 50 )
-
var product banana = fa_product.create ( &
...
price = void )
- Obix rule: By default, void values are not allowed.
- -> compile-time error
-
var product banana = fa_product.create ( &
...
price = foo.bar )
- -> immediate run-time error (if expression evaluates to void)
Contract programming (Design By Contract)
3 important questions
- Is this something we need often?
- Can we do this if the programming language doesn't support it?
- How easy or painful is it to do it?
People only use things if they are easy to use!
Date
type date
attribute year
attribute month
attribute day
end
Date
type date
attribute year type:positive32 end
attribute month type:positive32 end
attribute day type:positive32 end
end
Date
type date
attribute_list type:positive32
attribute year end
attribute month end
attribute day end
end
end
Date
type date
attribute_list type:positive32
attribute year end
attribute month check i_month <= 12 end
attribute day check i_day <= 31 end
end
end
Date
type date default_factory:yes
attribute_list type:positive32
attribute year end
attribute month check i_month <= 12 end
attribute day check i_day <= 31 end
end
end
Date
const date delivery_date = fa_date.create ( &
year = 2008 &
month = foo &
day = 1 )
Date
var positive32 foo
...
const date delivery_date = fa_date.create ( &
year = 2008 &
month = foo &
day = 1 )
Date
var positive32 foo
...
foo = elephant.age
...
const date delivery_date = fa_date.create ( &
year = 2008 &
month = foo &
day = 1 )
- no compile-time error!
- run-time error only if age of elephant > 12
- solution: 'feature redefinition in child types'
Feature redefinition in child type
Feature redefinition in child type
-
type month
inherit positive32
attribute value and_check: i_value <= 12.value end
end
end type
-
type date default_factory:yes
attribute year type:positive32 end
attribute month type:month end
attribute day type:positive32 end
end
Feature redefinition in child type
-
type day_of_month
inherit positive32
attribute value and_check: i_value <= 31.value end
end
end type
-
type date default_factory:yes
attribute year type:positive32 end
attribute month type:month end
attribute day type:day_of_month end
end
- now we get a compile-time error!
var positive32 foo = ...
const date delivery_date = fa_date.create ( &
year = 2008 &
month = foo &
day = 1 )
- ... and the new type can be reused
- ... and we can add useful features to the new type
Delivery date
- no deliveries on first day of month
-
type delivery_date
inherit date
attribute day and_check: not i_day.is_first_day_of_month end
end
end
-
type product default_factory:yes
attribute identifier type:positive32 end
attribute description type:string end
attribute vendor type:string end
attribute price type:zero_positive32 end
attribute first_delivered type:delivery_date end
end type
Conclusion
The aim of Obix is to help programmers to write more reliable and maintainable code through a unique combination of proven and innovative concepts which all support the important Fail fast! rule.
Experience shows that the Fail fast! rule increases productivity and reduces costs for software development.
Questions?
