syntax for text_field

Hi....
I have two tables named cis and software_cis which are polymorphically
related.
In the interface for editing the data in software_cis table, i specified
the text_field component as
    <label for="ci_name">Name</label>
    <%= text_field 'ci.content', 'name' %>

But it printed an error:
`@ci.content' is not allowed as an instance variable name

When i give <%= @ci.content.name%> the name field from software_cis
table is
printed. So please tell me the correct syntax of text_field. How can i
refer the software_cis table using model ci?

Regards
Suneeta