Introduction

QSOs represent the most energetic, sustained phenomena in the universe. They provide a stage for some of the most extreme physical conditions known to exist. While the energy budget is roughly the same across the entire electromagnetic spectrum, our knowledge of the central environment of these objects has come primarily from X-rays that crash through their centers and from the well known broad absorption line (BAL) phenomenon in the ultraviolet. In recent years, another piece of the QSO puzzle has emerged - narrow absorption lines (dv < 1000 km/s, NALs) which only partly occult the UV continuum and are, thus, clearly caused by gas close to the accretion disk [2,4,5]. For simplicity, hereafter, we refer to QSOs that host intrinsic narrow absorption as NALQSOs in the same spirit as BALQSOs. It is not known where NALQSOs fall into the general picture. It is also not completely known what properties of a QSO make it suitable to be a NALQSO. Low resolution optical surveys [1,3,7] for CIV have shown that high redshift, and large equivalent width associated systems tend to prefer steep spectrum radio-loud, optically faint QSO hosts. (An associated system is one that falls within 5,000 km/s of the emission redshift; it is not necessarily {\it intrinsic}.) This still leaves many unanswered questions. What about the population of weak associated absorbers? What happens at low redshift? Is the X-ray warm absorption phenomenon in QSOs connected to intrinsic UV absorption as in Seyfert 1s? The answers to these questions are not simple and require multivariate techniques to comprehensively address.