DB Design Question && Performance In MSSQL

Hi,


Can anyone put a name to the following type of design...


I need to be able to modify the amount/names of data "fields" stored
for an entity so instead of representing the data stored for an entity
in fields associated with that entity you would relate it to an another
entity which would contain a datafield type field and its associated
value, so different rows in the parent table could possibly have
different datafields associated with it.


E.g
The parent table is "person" and it holds common data amongst all
people - it has primary key of personID.
There is another table assoicated with person called "personDetails".
This would have fields "personID", "dataType" and "dataValue". It
might have records like the following:
personID, dataType, dataValue
1,phone,123456
1,email,t...@test.com
1,state,NSW
2,phone,987456321
2,state,VIC
3,phone,789456123


Of course this is just an example - the parent entity could be
anything.


I've seen a few XML files implement this type of design. e.g
<job>
<jobNumber>XYZ12345</jobNumber*>
<jobCreated>12-03-2005</jobCre*ated>
<jobdeatils>
<jobdetail type="WEIGHT">167</jobdetail>
<jobdetail type="WEIGHTMEASURE">KGS</jobd*etail>
<jobdetail type="CUBIC">45</jobdetail>
<jobdetail type="CUBICMEASURE">M3</jobdet*ail>
<jobdetail type="NUMPIECES">345</jobdetai*l>
</jobdetails>
</job>


Hope someone can put a name to this sort of design. I want to research
into this to see how people search effectively in this design and its
performance compared to traditional methods etc etc.

I would be implementing this design in MS SQL and it would be accessed
by an 400-500 users via ASP.NET.

Any help would be appreciated.


Thanks
Adam.