-- PedroRio - 21 Dec 2010

Business Object Language (BOL)

The Business Object Language is a small expression language to help define conditions for the behavior in XEO Object Models. It allows to reference attribute values, compare them with other values as well as making small calculations. The following sections explain the various operators and statements that can be used in the language.

Attributes

XEO Model attributes can be referenced in BOL expressions by their name, for example if you want to create an expression that represents the following ideia: "If the value of attribute X is bigger than 5, return true" the bol expression would be "if (x > 5) return true". This syntax works for attributes that are not Collection nor Object.

When dealing with a XEO Model attribute you can refer to the values of its attributes by using the separator '.' ; Imagine a situation where we have a XEO Model to represent a Person, a Car and a Car Brand, where Person has 1:1 relation to Car which has a 1:1 relation to Brand, those relations are depicted in figure BOL.1. The following tables have the definition of the Object Models.

Person ( Person )

Attribute Name	Attribute Type	Label	Description	Length	Required	Object Type
name	Text	Name	Person Name	30	-	N/A
avg_km_car_year	Number	Average Km's	Average KM's per year with a car	30	-	N/A
driver_license	Text	Driver License Number	The identifier of the driver license	30	-	N/A
ID	Text	Identifier	The identifier of the person	30	-	N/A
age	Number	Age	The age of the person	3	-	N/A
favorite_car	Text	Favorite Car	The favorite car of the person	30	-	N/A
car	Object	Car	The car of the person	30	-	Car

Car ( Car )

Attribute Name	Attribute Type	Label	Description	Length	Required	Object Type
model	Text	Model	The model of the car	30	-	N/A
age	Number	Age	The age of the car	3	-	N/A
kms	Number	Kilometers	The number of kilometers the car has done	4	-	N/A
brand	Object	Brand	The car brand	4	-	N/A

Brand ( Brand )

Attribute Name	Attribute Type	Label	Description	Length	Required	Object Type
name	Text	Name	Name of the category	30	true	N/A

Figure BOL.1 - XEO Models for the BOL example.

Tentar verificar se é possível usar "parent.att" em BOL

Boolean Values

Boolean values can be used in BOL expressions. The folowing expressions represent the "true" value:

• true
• yes
• y
• YES

In the same way, the following values represent the "false" value:

• false
• no
• n
• NO

Conditional Statements

In BOL you can use conditional expressions in the form of if/else statements. The syntax is like the following:

if ( CONDITION )
   BOL EXPRESSION
else
   BOL EXPRESSION

If you need more conditions you use if/else statements with brackets

if (CONDITION ){
  //BOL EXPRESSIONS
  //BOL EXPRESSIONS
} else {
  //BOL EXPRESSIONS
  //BOL EXPRESSIONS 
}

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Returning a value

Most BOL expressions are used in places where they must return a value (be it a boolean, string or numeric value). In order to do that BOL has the expression "return" which will return the result of evaluating the expression on its right side. Example:

return true

return YES

---

if (age > 18)
  return "You can drive"
else
  return "Need to wait a little longer"

Operators

BOL expressions can have multiple operands linked by operators (as with most programming languages). In BOL the following operators are allowed:

• > (Bigger)
• >= (Bigger or Equal)
• == (Equal)
• <= (Less or Equal)
• < (Less)
• ! (Negation)
• && ( And)
• || (Or)
• ! = (Different)

You can have expressions such as:

if (att1 > 2 && att2 != 45 && att3 == 'F') return "42"

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Functions

BOL includes a set of predefined functions which can be used inside every BOL Expression.

DATE FUNCTIONS

NOW - Returns the current date with time

TODAY - Returns the current date without time information

NOW_HOURS - Returns the current date with time information about the hour (discards minutes, seconds and mili-seconds)

NOW_MINUTES - Returns the current date with time information about the hour and minutes (discards seconds and mili-seconds)

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ROUND

ROUND(Number) - Rounds to the nearest integer (0.4 -> 0; 0.5 -> 1)

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CONCAT (Concatenates two values)

• CONCAT(String,String)
• CONCAT (Number,Number) - Number can be long/int value
• CONCAT (Object,Object) - Converts each Object to string and concatenates

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TO_DATE (Converts to a Date value)

• TO_DATE(Date, Format)
• TO_DATE (Object, Format), Object is converted to a String and converted to date
• TO_DATE (long, Format) - Convertes UNIX time miliseconds to a date

Format must be compatible with the ones accepted by SimpleDateFormatter (if the format is not correct it will simply return a null value)

The first argument can be one of the following functions (NOW, TODAY, NOW_MINUTES, NOW_HOURS, or any other valid date).

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SUM

• SUM ( Number , Number )
• SUM (Object , Object) - Converts the Object to Numbers and sums the numbers

Example:

Sum(3 , 1 ) will return 4

Sum (att1, att2 )  - assuming both are attributes which contain a value that can converted  to a number will return the sum of the two

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SUBTRACT

• SUBTRACT (Number, Number)
• SUBTRACT (Object, Object) - Converts the Object to String

Example:

Substract (3 , 1 ) will return 2

Subtract (att1, att2 ) - assuming both are attributes which contain a value that can converted to a number will return the difference between the two

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DIFF_IN_DAYS (Difference in days between two dates)

Returns the number of days between two dates

• DIFF_IN_DAYS (Date, Date)
• DIFF_IN_DAY (Date, Long)
• DIFF_IN_DAY (Long, Date)
• DIFF_IN_DAY (Long, Long)

Example:

DIFF_IN_DAYS (NOW, TO_DATE('22/12/2012','dd/MM/yyyy')) which will return the number of days between today and December 22nd, 2012

DIFF_IN_DAYS (TO_DATE('20/12/2012','dd/MM/yyyy'), TO_DATE('22/12/2012','dd/MM/yyyy')) which will return 2 (two)

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DIFF_IN_UTIL_DAYS (Difference in work days between two dates)

• DIFF_IN_UTIL_DAYS (Date, Date)
• DIFF_IN_UTIL_DAYS (Date, Long) - The long value is a Unix timestamp
• DIFF_IN_UTIL_DAYS (Long, Date) - The long value is a Unix timestamp
• DIFF_IN_UTIL_DAYS (Long, Long) - The long value is a Unix timestamp

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IS_NULL (Checks if a given value is null)

Works for all kinds of attributes except for Collection attributes. Returns true is the value of the attribute is null (i.e. newly created object will have all attributes null (except if they have a default value)).

Example:

if (IS_NULL (att1)) return true

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Examples

This section shows some examples of BOL expressions using the previous Model (Person, Car and Brand)

Figure BOL.2 - Examples of BOL Expressions

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