Property, Attribute, Parameter - difference?

> Hi,

>

> I know sounds silly, but what is the difference

> between Property, Attribute and Parameter? In what

> cases every of this words is used?

>

> Anton

Property: I use this word sometimes to refer to some property in a properties file. I can be used in XML, too. In a XML file you have properties.

Attribute: For me, it can have many meanings! I don't think that this word can have a specific meaning in programming. I'm not sure if this word can be used when you want to talk about some XML file. I think it can be used, yes.

Parameter: I use this word to refer to the parameter(s) of some method.

Marcelo9a at 2007-7-13 1:54:47 >

> Property: (...) in a Javabeans context, the two have different meanings,

> they just happen to often map directly to one another.

> Attribute: (...) Basically an element of the object's state,

> or the instance variable that holds it.

I second the main point there is an important difference between the two meanings: the abstract specification of observable state, and the implementation of it. And I agree with jverd's commented example for the usage of the terms.

As far as evocative terminology goes, the terms field and instance variable clearly refer to the "implementation" meaning.

On the other hand, as jverd pointed out, attribute or property are used more loosely, and can refer to both meanings.

AFAIMC, I deem they illustrate more the first, abstract meaning. But that's an opinion, and there doesn't seem to be a general consensus.

I was formally taught in CS course that attribute related to the abstract meaning.

The idea being that if the type Person has an attribute Age, the implementing classes can implement this attribute however they like (value stored in an instance variable, computation using another field, database query,...).

I haven't found my teacher's definition to be widely accepted over the Internet or even across my local colleagues, but I like the distinction, especially to prevent misinterpretation such as "Hey this class has lots of attributes, so it must use up much room in memory!".

A word on Parameter: I fear to sound a bit pedantic, but it is indeed used to mean several different things:

- jverd pointed out the most usual use of the term, synonym of a method's argument. Indeed Sun favors this latter term, argument. Again I happen to have been taught this way too.

- Parameter is also used in the expression Type Parameter (cf generics), in which case it is important to make the distinction with the arguments.

- Last but not least, due to the meaning of the word in the general language, parameter will often refer to anything that influence the course of an algorithm. To various people it can mean a constant, a configuration value read in a file, a global variable, a method's argument, or a completely external factor (as in "The number of concurrent users is a parameter that will affect the load of your database").

jdupreza at 2007-7-13 1:54:47 >

> A word on Parameter: I fear to sound a bit

> pedantic, but it is indeed used to mean several

> different things:

>

> ... etc. ...

Thanks for pointing that out. I should've known it wouldn't be that clear-cut. :-)

As for paramer vs. argument, I believe in CS there are definitions that relate one to the formal parameter (parameter, I think) and the other to the actual parameter (argument, I think), but I can never keep them straight, and I--and most people I know--tend to use parameter and argument pretty interhangeably when talking about "things you pass to a method."

jverda at 2007-7-13 1:54:47 >

Java et al:

An object is composed of attributes

attributes can hold a primitive or a reference

Attributes can be a method or a property

XML:

An element can have attribute (names) and (attribute) values

an element has an opening and a closing tag

attributes and values are inside the opening tag

<bodyelement attribute="value></bodyelement>

CSS:

selector.class { property:value; }

body.myclassname { left:5px; }

Clear to everyone?">

HaraldHopelessa at 2007-7-13 1:54:47 >