"Daniel" isn't the momentous tear-jerker it aspires to be, but it certainly has its impressive, revealing moments.

For all its miscalculations and solemnities, director Sidney Lumet's adaptation of E.L. Doctorow's 1971 novel--which used the Rosenberg spy case as a springboard for fictionalized domestic pathos and revisionist Cold War history--emerges as a compelling sort of failure at dramatizing a difficult, significant subject.

Lumet and Doctorow have gone out of their way to insist that the plot of "Daniel" should not be confused with the controversial body of speculation surrounding the Rosenberg case. Although the fictional work never divorces itself far enough from the historical episode to achieve autonomous artistic identity, one can sympathize with the filmmakers' tactical needs. The movie's ramshackle structure, though, remains a liability. Along with some oddly discordant performances, it creates an abiding confusion about where to draw the line between fact and fiction.

"Daniel," which opens today at the K-B Cinema, is at its most effective when immersed in background impressions of lower-middle-class Jewish and Communist family life in New York City during the 1930s and '40s. It's this relatively unfamiliar slice of private life that gives the picture individuality. But the movie is much more prone to melodramatic cliche' and special pleading after Daniel's ill-fated parents, Paul and Rochelle Isaacson, are compromised by a notorious public identity along the lines of Julius and Ethel Rosenberg.

Rank-and-file Communist Party members who may or may not be espionage agents as well, Paul and Rochelle are sentenced to the electric chair after being convicted of conspiracy. The filmmakers decline to judge if they're guilty and suggest that it's a dispute that must be transcended in the long run anyway, at least for the peace of mind of the Isaacson children, Daniel and Susan, who are orphaned by their parents' calamity.

Daniel, portrayed for the most part by Timothy Hutton, is introduced as the protagonist and principal narrator in 1967, when he's a graduate student at Columbia. He follows an inconclusive trail of evidence that seems to grow cold without resolving any questions about his parents.

Lumet and Doctorow content themselves with a tepid upbeat fade-out, losing Daniel, his wife and their baby son in the throng at a Central Park political demonstration. This immersion in the mass seems to imply that he's come through emotionally intact, and that a new activist generation has made peace with a tragically haunted heritage. Sweet sentiments, I suppose, but Daniel's stability remains as debatable as his likability as the movie flickers out.

Like the novel, the film has an annoying habit of picking up and discarding Daniel as the narrator. The past and present are interwoven with plenty of clumsy stitching, the styles of dramatic presentation diverging inexplicably from one sequence to the next. The overall storytelling rhythm is unbalanced. The fresh and intriguing early sequences, which concentrate on reproducing the culture of a Communist family group in a particular American time and place, with special emphasis on a child's perception of that experience, are paced briskly.

The tempo slows to a grueling crawl in the second half, when the filmmakers become obsessed with the Isaacsons' suffering. A prison reunion between mother and children is followed by a reprise for father and children. Then there are separate electrocutions, followed by a pair of funeral sequences. This woe-woe-woe half of the movie is the section that could profit from incisive direction.

One of the structural drawbacks is that the story reaches an emotional and metaphorical climax in the early going and never really improves on this highlight. The sequence depicts Daniel and Susan arriving late at a protest rally for their imprisoned parents in the company of Ascher, the Isaacsons' wearily dedicated lawyer played by Edward Asner. Since the crowd makes it impossible for them to reach the platform, the children are lifted and passed over the top from hand to hand until they're on the platform. The two little kids bob like miniature boats along the crest of this sea of anonymous sympathetic humanity and then stand clutching each other on stage, bombarded by the superbly ironic shout "Free Them! Free Them!" It's an extraordinarily evocative spectacle, summing up the hostages-to-political-misfortune destiny that awaits Daniel and Susan.

"Daniel" never goes beyond this expressive peak. There is, however, a second poignant interlude involving the children and it works almost as well. While briefly boarded at an orphanage, the children leave and hike all the way back to the abandoned family home in the Bronx, accompanied by the sound of Paul Robeson singing "This Little Light of Mine." Although an appropriate musical background for this material, Robeson's songs are used a bit too often and sometimes with painful "ironic" intent. In this instance the audio-visual mix works with a mysterious impact, and the sequence even transcends its sentimental obviousness.

The level of performance fluctuates as maddeningly as the level of depiction.

As an older Susan, Amanda Plummer sustains a pitch of craziness so high that it tends to inhibit pathos. The role is more rhetorical than human to begin with, a victimization cameo, but Lumet could have done the actress and the audience a favor by modulating Doctorow's excesses.

Lindsay Crouse proves such a tower of strength as Rochelle Isaacson that you regret the failure to enlarge her characterization, particularly in ways that would prepare us properly for a woman capable of ferocious ideological theater on the brink of death; entering the chamber, Rochelle throws out a rabbi, kisses a black matron and declares, "Let our deaths be my son's bar mitzvah!"

Mandy Patinkin, very good in many of his early scenes as Paul Isaacson, especially a revealing interlude in which he lectures little Danny on the evils of commercialism as exemplified by Joe DiMaggio's endorsement of Wheaties, can't survive two terrible showcase scenes--a modified Tevye act in which he lifts his infant son in dance and a bughouse act in the Big House. The cuckoo bits obscure the interesting element of fanaticism he expresses in calm moments--the sense of a loving father driven to distort and spoil things for his kid by the compulsion to indoctrinate.

Tovah Feldshuh takes the movie in hand at a particularly sluggish last-act juncture and provides it with a salutary jolt of intensity and dramatic resistance, while mopping up the screen with Timothy Hutton in the process.

Daniel is a character who tends to disintegrate as the story unfolds, making his maximum impression in flashback as a little boy and growing into something barely tolerable in the present. Doctorow burdens him with rather hateful streaks of contemptuousness at the grad student stage. For example, he's very curt with his devoted, bovine young wife (Ellen Barkin, wasted on a minor assignment), and this snottiness is never satisfactorily atoned for. Hutton is a peculiar ethnic choice to begin with--the character's "Jewish" identity seems to depend on his depiction as a hippie. It's more of a misfortune that Hutton seems emotionally straitjacketed, unable to project a personality that would make Daniel more authentic and sympathetic, less marginal and smug.

Lumet has a wealth of acting talent on hand, but he never achieves a satisfying ensemble effect and leaves you baffled about the intentions behind many individual performances. DANIEL

Directed by Sidney Lumet; screenplay by E.L. Doctorow, from his novel, "The Book of Daniel"; produced by Burt Harris. Presented by Paramount Pictures. Rated R. THE CAST Timothy Hutton . . . . Daniel Lewin (Isaacson) Amanda Plummer . . . . Susan Lewin (Isaacson) Lindsay Crouse . . . .Rochelle (Isaacson) Mandy Patinkin . . . . Paul (Isaacson) Edward Asner. . . . Jacob Ascher Tovah Feldshuh . . . . Linda Mindish John Rubinstein . . . . Robert Lewin