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                                                                     EXHIBIT 8.1

                           FOLEY, HOAG & ELIOT LLP
                           ONE POST OFFICE SQUARE
                         BOSTON, MASSACHUSETTS 02109



                                July 18, 1996



Bachman Information Systems, Inc.
Eight New England Executive Park
Burlington, Massachusetts 01803

                  Re:  Merger of B.C. Acquisition Corp.
                      into Cadre Technologies Inc.
                      ---------------------------------

Gentlemen:

      This opinion is delivered to you for the purpose of satisfying a condition
set forth in Section 7.1.7 of the Agreement and Plan of Merger dated March 25,
1996 (the "Agreement") by and among Bachman Information Systems, Inc., a
Massachusetts corporation ("Bachman"), B.C. Acquisition Corp., a Delaware
corporation and wholly owned subsidiary of Bachman ("Sub"), and Cadre
Technologies Inc., a Delaware corporation ("Cadre"), pursuant to which Sub will
merge with and into Cadre. Capitalized terms not defined herein shall have the
meanings set forth in the Agreement.

      We are counsel to Bachman and, as such, have participated in the Merger.
In providing this opinion, we have received, and have relied on, the statements,
covenants, representations and warranties contained in the Agreement, the
Company Affiliate Agreements, the Escrow Agreement, the representation
certificates of Bachman and Sub dated July 18, 1996, of Cadre dated July 18,
1996, and of certain Stockholders delivered in connection with this opinion
(collectively, the "Representation Certificates"), and such other documents as
we have considered necessary or advisable in rendering this opinion. Although we
have made inquiries with respect to such matters as we have considered necessary
or advisable in rendering this opinion, we have not made any independent review
or investigation as to factual matters in connection herewith.

      We have assumed for purposes hereof that (i) the copies or originals of
the agreements, instruments and other documents furnished to us are accurate (if
a copy) or authentic (if an original), and those that are agreements or
instruments have been or will be duly executed and delivered by all parties
thereto; (ii) the Merger will be consummated as set forth in the foregoing


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Bachman Information Systems, Inc.
July 18, 1996
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documents, including, without limitation, the Agreement, the Parent Affiliate
Agreements, the Company Affiliate Agreements, the Escrow Agreement and the
Representation Certificates; (iii) the representations made in the foregoing
documents or otherwise made in connection therewith are, and will continue to
be, true and complete, and no default or waiver exists in connection with the
foregoing documents; and (iv) no actions will be taken, no change in the
foregoing documents will occur, and no other events will occur, that would have
the effect of altering the facts, documents or assumptions upon which this
opinion is based.

      We express no opinion herein with respect to the laws of any state or
jurisdiction other than the federal income tax laws of the United States of
America, or with respect to any issue not specifically addressed below, or with
respect to whether the parties to the Merger are eligible or would receive a
favorable advance ruling from the Internal Revenue Service regarding any issue
addressed below. In particular, we express no opinion regarding (i) whether any
Stockholder will recognize income or gain as a result of the Merger or whether
any Stockholder who has provided or will provide services to Cadre, Bachman or
Sub will recognize income as a result of, or in connection with, such services,
and the effect of any such income, including, without limitation, the effect of
any such income on the basis and holding period of Parent Stock received by such
Stockholder in the Merger, (ii) other than as specifically addressed below, the
corporate income tax consequences of the Merger to Bachman, Sub and Cadre, (iii)
the effect, if any, of the "golden parachute" provisions of Sections 280G, 3121
and 4999 of the Code, the alternative minimum tax provisions of Sections 55, 56
and 57 of the Code, or the provisions of Sections 305, 306, 357 and 424 of the
Code, and the adjusted basis of any equity interest in Cadre held by Bachman
after the Merger, (iv) the corporate income tax consequences to Bachman, Sub and
Cadre of any transactions entered into in connection with or contemporaneously
with the Merger, (v) the effect of the Merger on any federal income tax
attributes or elections of Bachman, Sub and Cadre, (vi) the effect of the Merger
on any transaction in which Cadre stock or any option, warrant, escrowed stock,
convertible security, contractual right or other right to acquire Cadre stock
was received, and (vii) the income tax consequences of the Merger that may be
relevant to particular classes of Cadre Stockholders, such as dealers in
securities and foreign persons.

      The following opinions are based on present provisions of the Code, final
and temporary Treasury regulations thereunder, administrative interpretations
thereof and court decisions. Consequently, future changes in the Code, Treasury
regulations or administrative interpretations thereof, or future court
decisions, might result in federal income tax consequences that are materially
different from that described herein, and might apply retroactively to
transactions previously consummated.

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Bachman Information Systems, Inc.
July 18, 1996
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      Based upon and subject to the foregoing, it is our opinion that, for
federal income tax purposes:

      1. The Merger will constitute a "reorganization" within the meaning of
Section 368(a) of the Code, with each of Bachman, Sub and Cadre qualifying as a
"party to the reorganization" under Section 368(b) of the Code.

      2. Bachman and Sub will not recognize material amounts of gain or loss 
solely as a result of the Merger.

      We are furnishing this letter to you solely for the purpose of satisfying
the condition set forth in Section 7.1.7 of the Agreement. This opinion may not
be used, quoted, referred to or relied upon for any other purpose or by any
other person or entity without our prior written consent, except for all
references to this opinion contained in the Registration Statement.

                                          Very truly yours,

                                          FOLEY, HOAG & ELIOT LLP


                                          By:  /s/ Bruce A. Kinn
                                              ----------------------------------
                                              A Partner


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