Five - Selection of Locus for Searching or Placement

Chapter Table of Contents

The following suggestions are offered for selecting a class whenever the appropriate class for a particular claimed invention is unknown. These suggestions should be applied to each claimed invention.

A. Selecting a Class

1. Index to the U.S. Patent Classification System

Reference to the Index to the U.S. Patent Classification System by patent title, a key word of the title, a synonym thereof, or any other descriptor of the claimed disclosure should provide one or more clues to particular classes (and often subclasses) relating to the subject matter involved. Caution should be used with respect to the subclass(es) indicated under any heading (see Section V, B).

2. Patent Office Classes Arranged by Related Subject

Consult Classes Within the U.S. Classification System Arranged by Related Subjects since it is often the best method of making an initial determination of the pertinent class(es).

3. Alphabetic or Numeric Listing of Classes

Reference to Classes Arranged in Alphabetical Order or the numerical listing of class titles in the Classes Arranged Numerically With Art Unit and Search Room Locations may provide the necessary clue to the proper class.

4. Electronic Search Tools

Prior to the introduction of our current text searching database (BRS, and its clients EAST and WEST) USPTO used a database that allowed examiners to obtain a report on the frequency distribution of classifications for documents in a search result set. BRS supports the "tally" command, which provides similar functionality as the previous search system. Unfortunately, the tally command is not currently supported by the BRS clients EAST and WEST, it only works in "native mode". It is anticipated that the tally function will eventually be usable from the client software. Until then, if examiners wish to get frequency distribution reports of classifications for the documents of result sets they should contact their Information Technology Resource Provider (ITRP), who generally has access to native BRS. Another electronic tool, the PLUS system, comprises walk-up workstations at which examiners may scan text in an application or patent. The PLUS system will produce as an output a listing of pertinent references for the scanned text, as well as a frequency correlated listing of the classifications for those references.

5. Subclass Titles

A quick scan of the subclass titles in a class suggested by suggestions of paragraphs 1-4 above is often very helpful in a first approximation of the pertinence of such a class to the subject matter being considered.

In every case, the definition of the indicated class must be checked to verify the propriety of the proposed class selection. This selection requires that a class, as defined and further explained in the class notes, encompass claimed disclosure to the exclusion of other classes. Usually, the definition and notes of a class indicate other classes in which provision is made for related subject matter and also set the lines of demarcation between and among such related subject matter. It should not be necessary to squeeze or "shoehorn" a patent disclosure to make it fit a particular class definition.

6. Exceptions and Caveats

(a) Unless the definitions specify otherwise, a claim to an article of manufacture (a box for Class 229) distinguished solely by the composition or stock material from which it is made (a particular form of corrugated paper for Class 428) is placed in the appropriate composition or stock material class¾contrary to the selection procedure set out above.

(b) A single claim to a hybrid of categories (such as a product defined only by a process for its preparation) is occasionally encountered in a patent or application. Under these circumstances, an application may be assigned to the proper process class for purposes of examination. If allowed, the claim should be classified in the proper product class and a cross-reference may be placed in the process class where the application was examined.

(c) Notes for the class definition of the class providing for a combination should be read for possible exception where the claimed disclosure is to a "nominal" combination. A nominal, or named, combination refers to a combination wherein one or more of the parts or steps thereof are recited so broadly, and without details, as to constitute a mere identification rather than a description of each part or step.

(d) Frequently an application is received that claims too much for placement in either an element or a subcombination class but does not claim enough subject matter to clearly meet the requirements of a combination class. In these instances, assignment is generally made to the class providing for the larger organization, i.e., the combination class, instead of assigning it down to the lesser organization, i.e., the element or subcombination class.

(e) As mentioned above, where the historical placement of patents having a particular claimed disclosure has been contrary to written definitions and notes, this overrides all other considerations and controls placement of like subject matter until such time as corrective reclassification is effected.

B. Selecting a Subclass Within a Class

After determining the most appropriate class to search or place a particular claimed invention, the next step is to determine which subclass best provides for the concept in question. It should be noted that many claims, particularly in the chemical classes, require more than one classification.

Use the following procedures to select the subclass(es) applicable to each individual claim in a patent or application (e.g., each claim must be considered separately for classification or search purposes). A separate, mandatory classification is required for each claim that is classifiable in a different subclass. Likewise, each claim in an application should be considered separately to determine all critical search locations.

Before beginning a discussion on subclass selection, the meanings of certain terms and phrases need explanation. The following schedule is a hypothetical system to sort and classify scrap in a junkyard. It will be used to help define those terms and phrases.

21 . With end fastener
22 . With flaccid cover
23 . . Removable
9 . Hollow
10 . . Perforated
11 . . Grooved
12 . Perforated
13 . Grooved
14 . Mineral
15 . . Metallic
16 . . . Aluminum
17 . . . Zinc
18 . Rubber
19 . Ivory

The above schedule is similar to an outline used to write a term paper, for example. Each indented heading (subclass) further qualifies the heading (sub­class) under which it is indented and, consequently, must be read as including all of the limitations of the superior heading (subclass). For example, subclass 10 is read as a perforated hollow ball and will only accept items having at least these attributes. The qualifier "at least" is used deliberately. The reasons for this qualification are explained below.

Subclass titles that do not have a dot imposed between the title and numeric designator for the subclass are referred to as a "Main Line" or "First Line" subclass, e.g., subclasses 1, 2, 3, 4, 5, etc. Indented subclasses are referred to by their level of indentation. Subclasses indented one level below a "Main Line" subclass are referred to as "Second Line" subclasses, e.g., subclasses 21, 22, and 9, in the above example. Subclasses indented one level below a "Second Line" subclass are referred to as "Third Line" subclasses, e.g., subclasses 23, 10, and so forth. All subclasses indented under a superior concept are generally referred to as that concept's "indents."

Subclasses positioned at the same level of indentation are also called "coordinate" subclasses, provided that a superior subclass is not located between the subclasses being compared. Thus, subclasses 21 and 22 are coordinate with respect to each other. Subclasses 22 and 9 are not coordinate, even though they are both "Second Line" subclasses, since subclasses 6, 7, and 8 intervene between these two subclasses. All "First Line" subclasses are coordinate with respect to each other since nothing can be superior to a "First Line" subclass.

1. Schedule Order

The order in which a subclass appears in the schedule establishes the order of superiority among the concepts provided for in the schedule. The number assigned to a subclass title has no importance other than to provide an address for the storage area in which the art resides. The location of the subclass title within a schedule hierarchy is paramount.

In a modern schedule, subject matter is hierarchically arranged, with the subclasses embracing the largest organization of elements, i.e., the most complicated structures provided for in the class, usually appearing higher in the schedule than simpler subject matter. The above schedule example shows this type of arrangement. The organization of a bar, plus a link and a ball (i.e., subclass 1, which is the largest assemblage of elements) appears higher in the schedule than the lesser assemblages of a bar plus a link, or a bar plus a ball or a link plus a ball. The simplest elements (e.g., bars, links, and balls) are found even lower.

The modern schedule is also usually characterized by the placement of a "MISCELLANEOUS" subclass at the end of the schedule (see subclass 20 in the previous example). Also, it frequently has a "COMBINED" subclass located about midway down the schedule's length.

The "COMBINED" and "MISCELLANEOUS" subclasses are similar in character. The "COMBINED" subclass acts as a miscellaneous collecting point for the basic subject matter of the class combined with subject matter provided for in another class when such combinations are not specifically provided for higher in the schedule. The "MISCELLANEOUS" subclass collects all subject matter properly placed below "COMBINED," for which no specific subclass is provided.

See Appendix A for further discussion of the details of a modern schedule.

As noted earlier, the classification system as it exists today was created in the last 100 years. Vestiges of older systems still exist in the system and it is important to distinguish the older classes from the modern classes since the classes were created using a different theory of schedule structure and art placement. When using the older classes, adjust search and placement strategies accordingly.

In older classes, the "MISCELLANEOUS" subclass almost always appears as the first subclass in the schedule array. In this position, the "MISCELLANEOUS" subclass assumes the function of both the "COMBINED" subclass and the "MISCELLANEOUS" subclass in the modern schedule. It provides a home for all unprovided for materials admitted to the class by its definition. It therefore accepts unprovided for combinations of the basic subject matter of the class and structure provided for in other classes, unprovided for basic subject matter, and unprovided for subcombinations or elements found in the class. When placing a document or conducting a search in an older class, visually scan the main lines below "MISCEL-LANEOUS" to see if any provide for the subject matter in question. If no subclass is found, placement in "MISCELLANEOUS" is proper.

2. Inclusive Nature of Subclasses

A second important characteristic exhibited by the classification schedules is the inclusive nature of subclasses. This means that a subclass is proper for any claimed disclosure that at least recites the subject matter provided for in the subclass.

Thus, in addition to providing a home for claims exclusively directed to the provided for subject matter, a subclass also accepts all combinations employing the provided for subject matter as a subcombination thereof, provided the combinations are otherwise proper for the class and do not find a home higher in the schedule. A subclass also provides for multiples of the concept unless a subclass is provided higher in the schedule for the multiples.

Given the concepts of hierarchy and the inclusive nature of subclasses, the modern classification schedules can be viewed as a series of sieves or strainers located one above another (see Illustration A on the next page). Those sieves that are located higher in the array have larger diameter apertures, so they strain out only the largest particles ¾ that is, the largest organization of claimed elements. Moving down through the series, the aperture size decreases, consequently trapping smaller sized organizations. This process continues all the way down the series to the bottom, i.e., the "MISCELLANEOUS" subclass, which traps whatever was not caught above.

If material is dropped into the top of the sieve array, it passes through the array until an aperture is reached that blocks further passage of the material. So it is with a modern classification schedule. When placing or retrieving (i.e., searching) a concept using a schedule, start with the first subclass in the class and proceed to move down through the "First Line" subclasses until one is found that will accept any claimed subject matter. This subclass exhausts the claimed subject matter and all concepts employing this subject matter. No lower "First Line" subclasses should have to be looked at in the schedule for this subject matter.


 Images of a series of sieves or strainers located one above another used to illustrate the hierarchy and inclusive nature of the modern schedule.

Illustration A

Since subclasses are inclusive, once an appropriate subclass is selected, it may be necessary to consider subclasses located higher in the schedule than the one selected. To illustrate, refer to the junkyard schedule given as an example in the Section above. Suppose, sorting through a pile of junk, a bar is discovered and a decision must be made about which bin to store the bar in. Consulting the schedule, starting at the top and scanning down, it is noted that subclass 1 provides for bars, but the bars must be combined with other elements, i.e., links and balls. Unless at least all three are present, classification in bin 1 is not proper.

If there is only a bar itself, then subclass 1 is not the proper placement for the bar. Subclasses 2 and 3 also provide for a bar. As noted above, the bar is combined with some other feature, i.e., a link in one case and a ball in the other. The first subclass that accepts a bar by itself is subclass 6. Accordingly, you would assign the bar to bin 6.

Now, suppose after a few months, someone comes in looking for a novel bar. It is known from previous experience that bars, per se, are in bin 6 and that in the classification system the subclasses or bins are exhaustive of their subject matter. Consequently, if the junk has been properly sorted, there is no need to look in any bin number that appears lower in the schedule than bin 6.

What about higher subclasses? Well, subclasses 1, 2, and 3 all include bars as part of their organ­ization. To ensure that all bars have been seen, look into those bins also.

Finally, once a subclass is selected, all of its indents (if there are any) must be investigated to be sure that one of them does not provide more fully for the subject matter under investigation. The processes to be used are discussed below under the heading of "General Methodology." Also, it is imperative to read the subclass definition and any notes attached to it to be sure that no exception is made to the general rule of the inclusive nature of subclasses. Such exceptions do occur and care must be taken to avoid wasting time and effort.

3. Additional Types of Art Collections

a. Digest

A digest is a collection of cross-references created by an examiner; it is based on a concept that relates to a class but not to any particular subclass of that class. No ORs may be placed in digests. Digests are listed in numerical sequence at the end of the class schedule. Digests are not defined and are not available in the Public Search Room file.

b. Cross-Reference Art Collection

Cross-reference art collections differ from digests in that the material involved in the cross-reference art collection is defined to some degree and the patents are available in the Public Search Room. Some of these art collections include indentation levels. Placement in these areas is intended to follow official patent placement procedures. Cross-reference art collections are usually listed in numerical sequence at the end of the class. In most classes, subclass numbers 900 - 999 are reserved for cross-reference art collections. Some cross-reference art collections may only be searched electronically (via EAST or WEST). Other cross-reference art collections are based on the European Classification (ECLA) system, which is an expansion of the International Patent Classification (IPC) system.

c. Alpha Subclasses

Over the years, Patent Examiners have created alpha subclasses (previously called "unofficial" subclasses) to facilitate searches within the arts under their jurisdiction. In this process, a grouping of patents is selected from an existing numeric subclass and then collected in a new indented subclass with an alpha designation following the numeric designation. Since the original subclass no longer has all the patents officially classified therein, it is given the alpha designation "R" (indicating residual). Note that the numeric subclass located in the Public Search Room equates to the residual subclass plus any alpha subclasses indented under it. There are no definitions for alpha subclasses, nor is it contemplated to define these subclasses beyond the context of the titles and the definitions of the subclasses from which they were formed (and which are now "R" subclasses). The indented alpha subclasses are positioned in their proper hierarchical location in the schedule (i.e., immediately above the next subclass having an indent level less than or equal to the "R" subclass). These art collections are offered only to the extent they may be helpful as a search assist and should not necessarily be considered to be a completed collection of the art represented by the title.

d. E-subclasses

Between 1979 and 1995, the USPTO regularly classified newly published foreign patent documents into the USPC. In an effort to address the lack of recently classified foreign documents in USPC and to advance the prospect of harmonization between USPC and ECLA, E-subclasses were created. E-subclasses are USPC subclasses that correspond in scope to a classification in the ECLA system on a one-for-one basis. They appear near the end of schedules for the classes they exist in, and like Cross-Reference Art Collections, cannot accept an "OR" or Primary classification.

E-subclasses are identified by their subclass numbers, which begin with the letter "E", and are followed by up to five numerical digits, for example, E29.122, E31.67. The definition of each E-subclass identifies the ECLA classification the E-subclass corresponds to and may additionally contain a statement regarding the basic subject matter of the subclass. For those that do not, examiners are advised to review the documents classified in the E-subclasses to determine their scopes, since the scope of the E-subclass may not be the same as that of the USPC class in which it exists. Not only do E-subclasses present an alternative search to the art presented by other USPC subclasses, they generally contain complete and up-to-date classifications of foreign documents as classified by the EPO. For example, if the title of an E-subclass ends with the suffix "(EPO)", then the subclasses are regularly updated with foreign documents classified by the EPO. If the E-subclass title ends with the suffix "(JPO)", the subclass is regularly updated with documents classified by the Japanese Patent Office (JPO). An E-subclass having both suffixes indicates it is regularly updated with foreign documents classified by both offices. An E-subclass created by U.S. examiners has no ECLA equivalent (typically created as a breakdown of some other E-subclass that does) has no such suffix and does not include foreign office classified documents. The parent subclass providing for the foreign documents must be searched to obtain them.

Some primary subclasses, i.e., regular numbered and alpha subclasses, have titles that begin with a parenthesized "(E)". This indicates that the subject matter of these subclasses correspond to that of some E-subclasses in the class. Whenever an examiner places a mandatory classification (i.e., an OR for a patent or a Primary for a PGPub document) into one of these subclasses, they usually should place at least one cross-reference in an E-subclass in the class. The classifications U.S. examiners place on U.S. documents in E-subclasses are reported to the EPO. EPO reports to the United States the foreign documents they classify in the corresponding ECLA. In this manner, each office shares the work of classifying the world's documents into a common classification scheme. Of course, an examiner can place a discretionary classification of any U.S. patent document in an E-subclass anytime.

For answers to specific questions concerning E-subclasses, send your questions to

e. FOR subclasses

In October 1995, USPTO stopped classifying new foreign documents into the USPC. At the same time, the routine reclassification of foreign documents as part of reclassification projects was also halted. Reclassification of foreign patent documents is now only performed on a limited basis. For those subclasses being reclassified where the cost of reclassifying foreign documents cannot be justified, the foreign documents are kept together in collections corresponding to the old, abolished USPC classifications. This preserves the intellectual effort used to create the original collections. When USPC subclasses are reclassified and their foreign documents are not, "FOR" subclasses are created to keep the foreign art collections intact.

Foreign art collections are found at the ends of the USPC classes in which they exist. They accept for classification only foreign patent documents and non-patent literature and can be identified by their subclass numbers which begin with "FOR", for example, FOR126. Typically, FOR100 is the lowest numbered foreign art collection. At the end of each foreign art collection title, in parentheses, is the subclass identifier of the abolished USPC subclass from which it came. The definitions of foreign art collections correspond to the definitions of the old abolished USPC subclasses from which the foreign art collections are derived. No superiority among foreign art collections should be assumed, except between those descended from a common ancestor. The reason for this is that a portion higher in a USPC class schedule may be reclassified after a lower portion of the schedule, and later created FOR subclasses are arranged after earlier created FOR subclasses.

Each utility class in the USPC has a special FOR subclass called "FOR000". These FOR subclasses do not contain foreign patent documents from abolished USPC subclasses. These special subclasses were created as "class level" subclasses for machine placement of foreign patent documents into the USPC. It was found from experimentation that a computer could generally determine with good accuracy which USPC class a foreign document ought to be classified into but not which subclass. The FOR000 subclasses solved that dilemma by giving a computer a place to classify foreign documents at the class level by placing them into the FOR000 subclasses when a more suitable subclass could not be determined.

4. General Methodology

(a) To reiterate, once the proper class is iden­tified, it is necessary to select the proper subclass by scanning down the schedule of the class from the first appearing subclass toward the last. Only First Line subclasses (all fully capitalized titles) are considered on the initial scan. Each First Line subclass is evaluated (title checked against the definition, if necessary) until a First Line subclass is reached that provides for that claimed disclosure. When a First Line subclass cannot be selected using the claimed disclosure, the claim is classified in the "MISCELLANEOUS" subclass ¾ even if a subclass can be selected using the total or unclaimed disclosure.

(b) Classifying by claimed invention. If such a First Line subclass has coordinate subclasses indented under it, these indented (Second Line) subclasses must in turn be scanned and evaluated individually to determine the first or highest subclass, if any, which provides more specifically for the claimed disclosure. See "Placement Within Alpha Arrays," below.

(c) If such an indented, Second Line subclass itself has coordinate indented subclasses, repeat the above process until the ultimate indented subclass is reached that provides for the claimed disclosure.

(d) In the event that a claim is classifiable in more than one subclass in a class, the highest appearing subclass in the schedule that provides for the subject matter of any claim controls the Original classification of the claim.

5. Genus-Species Rule

The genus-species rule assumes that each species subclass is mutually exclusive of all other species encompassed by their generic subclass. Therefore, in many class schedules exhibiting a genus-species relationship, a variant to the above combination-subcombination rule is followed.

In a genus-species subclass array when plural species are indented under the generic subclass, placement is on the basis of total disclosure where only generic claims appear in a patent having disclosed species. A patent having genus claims only, but disclosing only species provided for by indents, is placed in the first appearing disclosed species subclass.

A patent having genus claims only and a disclosure to an unprovided for species is placed in the generic subclass; the generic subclass is the first appearing subclass that can take the un­provided for species.

For example, in the following subclass array:

1 Generic subclass (SPRING, e.g., Torsion, etc.)

2 . Subclass species A (Coil)

3 . Subclass species B (Leaf)

(a) If a generic claim only is present with disclosure of species A and B, place the patent as an OR in subclass 2 (and XR it to subclass 3).

(b) If a generic claim only is present with disclosures of species A and C (Torsion spring), place the patent as an OR in the generic subclass 1 (and XR it to subclass 2).

Stated generally, where, in addition to the generic claim, there is a claim to a provided for species, the patent is placed as an OR in that species subclass unless there is also a claim to an unprovided for species. In this latter case the patent is placed in the generic subclass.

For example, in the subclass array above:

(c) If a generic claim as well as a claim to species A and a disclosure to species C is present, place the patent as an OR in subclass 2 (and XR it to generic subclass 1).

(d) If a claim to species C is present as well as a claim to species A, place the patent as an OR in generic subclass 1 (and XR it to subclass 2).

In all of the above instances, place XRs in the appropriate subclasses. Thus, for a generic search to be complete, it must include the genus subclass and all indented species; a complete search for a provided for species need be made in only that species subclass; and a complete search of an unprovided for species need be made only in the generic subclass. You must be aware, however, of the presence of species that are not mutually exclusive. In the example used above, assume the presence of a third indented species subclass entitled "Plastic" and located above sub­classes 2 and 3. Since any of the other species (i.e., torsion, coil, or leaf) could also be formed from a plastic material, none are mutually exclusive with respect to the "Plastic" species. Therefore, a search for either the torsion coil or leaf spring should include the subclass entitled "Plas­tic." One final note: if the "Plastic" spring subclass were located at the bottom of the array, a search for a coil or a leaf spring would be confined to subclasses 2 and 3, respectively. This is due to subclass schedule hierarchy, and the exhaustive nature of subclasses, which was explained in this Section, above.

6. Placement of Markush Type Claims

In chemical compound and composition cases, when there is a generic claim classifiable in a number of different classifications, the OR is placed as described above ¾ on the basis of the claimed species, or on the basis of the disclosed species if no species claims have been presented. In such cases, however, all classifications encompassed by the generic claim are mandatory.

In some chemical applications or patents, as sanctioned by Ex parte Markush, 1925 C.D. 126, a "genus" claim may be set forth as a group consisting of certain specified materials, when there is available no commonly accepted generic expression commensurate in scope with the materials recited (see MPEP 706.03(y)). An application or a patent may thus have a Markush "genus" claim with or without other claims to the specified materials, per se, and such specified materials being "species" of the Markush "genus." The same principles set forth above, with respect to genus-species array, govern the placement of applications or patents with Markush type claims. For example, given the following subclass array:

1 Generic subclass (organic compound)

2 . Species subclass (A) - ester

3 . Species subclass (B) - alcohol

(a) When a Markush group is disclosed, but only claimed as "species A (ester)" and "species B (alcohol)," place the document as an "Original" in subclass 2 and XR it to species B in subclass 3.

(b) When a Markush group is claimed as "consisting of A (ester), B (alcohol), and C (ether)," place the original in generic subclass 1 and XR it to species subclasses 2 and 3. The individual members of the Markush group are treated independently and the member C is provided for only in the generic subclass 1.

(c) When a Markush group is claimed as "consisting of A (ester), B (alcohol), and C (ether)," and there is also a claim to A (ester), per se, the original class­ification is to species subclass 2 with an XR to generic subclass 1 and to species subclass 3. That is, a patent having a claim to a Markush group is placed as an original in the genus subclass only when individual species are not claimed. The classification of the claimed species controls placement of the original.

7. Mixed Array (Genus-Species and Combination-Subcombination)

A subclass schedule that includes both combination subclasses and species subclasses indented under a common genus-subcombination subclass is categorized as a mixed array (see the list below).

1 SPRING (subcombination of a mechanism)

2 . Coil (species A of spring)

3 . Leaf (species B of spring)

4 . With Indicator (combination)

5. With Lubricating Means (combination)

The following rules of placement have been used for mixed arrays:

(a) When a combination or subcombination is claimed which includes a coil spring (A), place the OR in subclass 2. No XR is needed since by schedule superiority all subject matter, including A, should be in subclass 2.

(b) When one claim includes a coil spring, plus an indicating means and a second claim includes a torsion spring (an unprovided for species) plus an indicating means, place the OR in subclass 2 with an XR to subclass 4. All coil springs and combinations claiming a coil spring are in subclass 2 and all combinations, including an indicating means, not provided for in the preceding subclasses, are in subclass 4.

(c) When one claim is to a coil spring plus an indicating means and a second claim is to a torsion spring, per se, place the OR in the generic subclass 1, the subclass accepting an unprovided for species, with an XR to subclass 2.

(d) When one claim is to a coil spring plus an indicating means and a second claim is to a torsion spring plus an unprovided for element Z, place the OR in subclass 1 with an XR to subclass 2 -- as in (c) above.

8. Placement Within Alpha Arrays

The alpha subclasses provide for original and mandatory classifications. In the past, indented alpha subclasses were located directly under the subclass from which they were taken (i.e., directly under the residual or "R" subclass). This often caused confusion in determining a proper search field and in properly classifying a document. To help avoid this confusion, all indented alpha subclasses were relocated to their proper position in the schedule hierarchy (i.e., immediately above the next subclass having an indent level less than or equal to the "R" subclass from which they were taken). Patent placement in indented alpha subclasses now follows all normal rules of placement for subclasses.

In the sample alpha array below, indented alpha subclass 273N was created from subclass 273R. If, after considering each two dot indented subclass under subclass 273R (i.e., subclasses 274, 276, 277, 278, 279, 281R, and 284.1), a proper classification has still not been found, then alpha subclass 273N should be considered.

273R . Bituminous material or tarry residue containing
274 . . With sulfurizing or sulfonating agent
275 . . . With filler, dye or pigment
276 . . Rock asphalt
277 . . Bituminous emulsion
278 . . With solvent or dispersing medium
279 . . With flux
280 . . . With filler, dye or pigment
281R . . With filler, dye or pigment
282 . . . Fibrous containing
283 . . . Water containing
281N . . . Nitrogen containing
284.1 . . Phosphorus containing
273N . . Nitrogen containing
285 . Hydrocarbon containing

The user must be aware, however, that many old indented alpha subclasses may contain patents that were not consistently placed according to the rules of superiority. Also, since no definitions exist for any of the indented alpha subclasses, the user may have to look at the patents in each indented alpha subclass as well as the parent residual ("R") subclass to determine what type of subject matter is classified there. In the example above, even though subclass 273N might seem to be the proper classification, consideration of subclass 273R would still be proper. Subclass 273N would not have a definition, which might result in subclass 273R containing patents that might be relevant to the user's needs.

Proper patent placement into alpha subclasses is even more difficult when a series of alpha subclasses is listed sequen­tially. Again, since there are no definitions and since it is not known whether official rules of patent placement were followed in the past, a search in these areas could involve searching all of the alpha subclasses as well as the residual R subclass.

9. Nonconformity in Practice

It is necessary to be on the alert for past diversity of practice respecting placement within a class based on disclosure. Thus, vary your search techniques to compensate for such diversity. Nonconformity has nearly always been of the following type:

In some cases, the combination-subcombination practice of carrying placement to an indented combination subclass has been extended unoffi­cially to a genus-species subclass array. In such an instance, an unprovided for species, even when claimed, has been assigned to a subclass providing for another species which has also been disclosed. This has often been done with no cross-reference back to the generic parent subclass. When such a condition is known or detected, an unprovided for species must be searched in the parent generic subclass as well as all species subclasses indented thereunder.

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