In order to avoid inconsistencies, multiple interpretations and over-generalization FRBRoo analyses and specializes FRBRer’s group 1 entities by establishing new, more concrete entities, and classifies them under CRM’s classes E28 Conceptual object or E18 Physical thing. FRBRer's work, expression and item remains the same while "manifestation" is split into two entities, the F3 Manifestation Product Type and the F4 Manifestation Singleton, in order to cover both the conceptual and physical notion.

FRBRoo retains the general notion of FRBRer’s entity “Work” and defines F1 Work as the sums of concepts which appear in the course of the coherent evolution of an original idea into one or more expressions  that are dominated by the original idea.

However a further analysis unpacked a few other interpretations...

A work may contain expressions from other works in order to enhance or add value to them , without altering them.

In continuation, a work may result in sequences of Expressions or Manifestations with common features. This kind of work is expressed throught the class F18 Serial work, which is a subclass of F19 Publication work and of F15 Complex work. For the documentation of serials and other continuing resources the National Library of France and the ISSN International Centre developped an extension of FRBRoo, the  PRESSoo.

Works may be related to each other through different relationships. We will now see how FRBRoo models these relationships.
First of all, as we mentioned previously, in FRBRoo we have the class F15 Complex work which is composed of several structural parts, consequently expressed in more than one complete set of signs, conceptually linked to each other. FRBRoo considers these parts as individual works that are “members” of a complex work. So, the member relationship of Work is based on the conceptual relationship and should not be confused with the internal structural parts of an individual expression. So members of a complex work can be the various translations of a work, or the various editions, versions or states. The important thing is that the set of concepts of a complex work dominates in its members. For example, Goethe's "Faust" is a play in two parts. The first part was first published in 1808 and the second part was finished in 1831 and published in 1832.  The two parts are considered members of the Complex work of “Faust”

To continue with the relationships that may connect works, there are many cases where a work is the subject of another work. For example "Hamlet and His Problems” is an essay written by T.S. Eliot in 1919 that offers a critical reading of Hamlet. So it is a work about Shakespeare’s Hamlet.  In 2013 S. Rengachari wrote an analysis on Eliot’s essay on Hamlet. 

However, it distinguishes between expressions that convey the complete idea of the work they realize (F22 Self-contained expression) and expressions that, deliberately or by accident, convey only a fragment of the idea of the work they realize (F23 Expression fragment). F23 Expression fragment was not intended by its creator to make sense by itself.

Expressions may be related between them through different kinds of relationships. For example an expression may incorporate an expression from another work. In some cases a work may include material from other works and this is what FRBRoo names a container work. This inclusion relationship does not hold at the level of ideas but only at the level of signs. We shouldn't talk about a work incorporating another work but about the self-contained expression of this work that may incorporate already existing self-contained expressions of other works. For example the sonic content of the second volume of the CD entitled “the No. 1 DJ collection 70’s"  incorporates 19 songs by various singers. Either the whole sonic content of the CD or each song separately, is considered as an instance of a F22 Self-contained expression because it is a complete set of signs that conveys the complete idea of the work it realises.

When a work is a member of a complex work,  the complete set of signs that conveys the complete concept of the work is a structural part (a component) of the larger set of signs that convey the concept of the overall work, the complex work. For example the Divine Comedy, the epic poem by Dante Alighieri, is divided into three parts: Inferno, Purgatorio, and Paradiso. These three parts are considered as individual works and as members of the complex work "Divine Comedy". Consequently the self-contained expressions of the three works are components of the overall expression of the “Divine Comedy”.

As already seen at the beginning of this section, FRBRoo distinguishes between works expressed in just one set of signs and those expressed in more than one set of signs.  The first case of works that are uniquely and completely expressed in a single set of signs (in one self-contained expression) is what FRBRoo calls Individual works. An individual work represents the concept as expressed by precisely this unique set of signs. It does not have other works as parts. From the elaboration or logical coherence of its content , the outcome is considered as complete.

Contrary to Individual works, a Complex work is a work that is composed  of several structural parts, though, it is expressed in more than one complete sets of signs that have a conceptual unity between them. This can happen either because the author decided to realize the work in several parts or because it was later taken up by another creator who acquired the spirit of the initial concept. In this last case a complex work is never finished in an absolute sense.

Each individual state of an etching, as a Self-Contained Expression, conveys its own F14 Individual Work and is regarded as part of the larger, abstract F15 Complex Work that encompasses all distinct states of the same etching. A shortcut is possible to represent the relation between the complex work with the two different expressions.

Don Quixote is a complex work realized in two parts. These are two different complete sets of signs, each of them being a structural component of a larger set of signs. Each part conveys in itself the complete concept of a work that is member of (R10) the overall work of Don Quixote. A shortcut is possible to represent the relation between the complex work with the two different expressions that realize it.

“Christ Recrucified” was written in late 1948 by Nikos Kazantzakis. We consider Kazantzaki's work to be an individual work because at that time it was realised in a single set of signs which is the author’s text, an instance of F22 Self-contained expression. There weren't any parts or any derivatives of the work yet, but the original text of the author.

The fact that a new self-contained expression was created through the translation of Kazantzakis's text,  which kept the initial conceptual content of the work makes “Christ recrucified” a Complex work that has two members, Kazantzaki’s contribution and the translator’s contribution, so it is realised in two self-contained expressions, the original text and the english text.

The following year, in 1956, Jules Dassin worked with Kazantzakis to produce a script for the film entitled “Celui qui doit mourir”. This film adaptation is  considered a new member of the complex work, since it preserves the initial idea and it is considered also a derivative work, deriving from the set of concepts of Kazantzakis’s work

As already seen, an expression may incorporate another already existing expression or a part of an expression. This happens when a work reuses some already existing material in order to produce some new creation. FRBRoo defines F16 Container work as the class that comprises works whose essence is to enhance or add value to expressions from one or more other works without altering them, by the selection arrangement and/or addition of features of different form such as layout to words, recitation and movement to texts, instrumentation to musical scores.
As seen, the inclusion relationship holds only at the level of signs. The collected expressions are integral part of the containing expression but the works of the collected expressions do not become part of the container work.
Aggregation , publication and performance works are all container works.

The Beatles' Ballads is a compilation album featuring a selection of ballad songs by The Beatles. It is an aggregation work since it aggregates expressions from different works, i.e. different songs of Beatles. In the same way, an anthology of poems or the proceedings from a colloquium are instances of F17 Aggregation work because they make use of expressions of the individual poems or papers that have been selected and ordered as part of an intellectual process.

The concept on behalf of the publisher of issuing together all works of Vermeer under the title “Vermeer: the complete paintings” and making decisions on the layout, the image for the frontcover etc. is demonstrating the publisher’s intellectual contribution to this publication. This contribution is the publication work. As a publication work, it is also a container work since it contains expressions from other works, it uses a picture of Vermeer’s painting to decorate the front cover of the book and it incorporates the authorial text and other pictures of Vermeer’s paintings. It may also be considered an aggregation work since it aggregates expressions from different works, i.e. the individual paintings of Vermeer.

For example, Hamlet is one of the most revived scripts in western drama. A F20 performance work of Hamlet  takes shape when the F25 Performance plan is realised.  In the case of a theatrical performance, the F25 Performance Plan, which includes any staging directions that convey a given director’s vision of ‘Hamlet’ must necessarily incorporate the text of ‘Hamlet’, the original or an adapted version of it. In case of a musical performance, the Hamlet opera for example, the performance plan will include  a musical score.  Any work that is based on Shakespeare's text of Hamlet, either altering the content or not, is considered a derivative work and a member of the complex work named "Hamlet".

The concept of recording is not necessarily linked to the use of modern devices that allow for mechanical recording, such as tape recorders or cameras. However, in practice, library catalogues tend to regard as recordings only the products of such mechanical devices. But the concept of recording is very much linked to the notion that there is something that is recorded. In general, photographs or animated images are not to be regarded as instances of F21 Recording Work just because of the use of the medium, but simply as instances of F1 Work (or F15 Complex Work). Only such photographs and animated images that can be used as documentation are to be regarded as recordings.

In order for FRBRoo to cover the physical interpretation, that of the “physical embodiment of an expression of a work”it  introduces the class F4 Manifestation Singleton. F4 Manifestation Singleton is declared as a subclass of the CIDOC CRM class E24 Physical Man-Made Thing, and therefore as a subclass, too, of the CIDOC CRM class E18 Physical Thing.

A Manifestation singleton is the first manifestation of the work in the real world that comes together with creating the first set of signs (expression). It is produced as a unique object, such as a manuscript. Any instance of Manifestation Singleton must always carry an instance of F2 Expression.
 

Manifestation Product Type defines all of the features or traits that the exemplars of a given publication “are supposed to” or “should” display in order to be recognised as copies of this particular publication. These features include: one instance of F24 Publication Expression (that has incorporated the authorial expression)  and all additional input by the publisher such as graphics and layout etc. and the appropriate types of physical features for that form of the object (number of parts, material, dimension etc.) To model the relationships between the manifestation product type  and all the features an exemplar should have, FRBRoo uses a series of “CLP” properties, i.e., “class properties”.
Last but not least, if all but one copy of a given publication are destroyed, then that copy does not become an instance of F4 Manifestation Singleton, because it was produced together with sibling copies, even though it now happens to be unique.

The concept of FRBR’s last intellectual product, the Item, stays the same in FRBRoo. Item is a physical object, an exemplar such as a printed book or a CD  that carries a publication expression and it is produced by an industrial process involving a Manifestation Product Type. In other words, an instance of F5 Item is what we call “copy”, an industrial product - one out of many produced through the same industrial process. All these copies share the same characteristics. It is introduced as a subclass of CRM’s E84 Information Carrier, thus, subclass of E18 Physical thing.