Patent Publication Number: US-10318757-B1

Title: Dynamic hierarchical generalization of confidential data in a computer system

Description:
TECHNICAL FIELD 
     The present disclosure generally relates to computer technology for solving technical challenges in collection and maintenance of confidential data in a computer system. More specifically, the present disclosure relates to performing a dynamic hierarchical generalization of confidential data in a computer system. 
     BACKGROUND 
     In various types of computer systems, there may be a need to collect, maintain, and utilize confidential data. In some instances, users may be reluctant to share this confidential information over privacy concerns. These concerns extend not only to pure security concerns, such as concerns over whether third parties such as hackers may gain access to the confidential data, but also to how the computer system itself may utilize the confidential data. With certain types of data, users providing the data may be somewhat comfortable with uses of the data that maintain anonymity, such as the confidential data merely being used to provide broad statistical analysis to other users. 
     One example of such confidential data is salary/compensation information. It may be desirable for a service such as a social networking service to entice its members to provide information about their salary or other work-related compensation in order to provide members with insights as to various metrics regarding salary/compensation, such as an average salary for a particular job type in a particular city. There are technical challenges encountered, however, in ensuring that such confidential information remains confidential and is only used for specific purposes, and it can be difficult to convince members to provide such confidential information due to their concerns that these technical challenges may not be met. Additionally, even once these concerns are met, it can be challenging to provide relevant insights from the confidential data as submitted confidential data is often provided at such a granular level that generalizations are needed in order to have enough data to make an accurate insight, but overgeneralization causes the insights to be less relevant. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Some embodiments of the technology are illustrated, by way of example and not limitation, in the figures of the accompanying drawings. 
         FIG. 1  is a block diagram illustrating a confidential data collection, tracking, and usage system, in accordance with an example embodiment. 
         FIGS. 2A-2C  are screen captures illustrating an example of a user interface provided by a confidential data frontend, in accordance with an example embodiment. 
         FIG. 3  is a flow diagram illustrating a method for confidential data collection and storage, in accordance with an example embodiment. 
         FIG. 4  is a diagram illustrating an example of a submission table, in accordance with an example embodiment. 
         FIG. 5  is a flow diagram illustrating a method for confidential data collection and storage, in accordance with an example embodiment. 
         FIG. 6  is a diagram illustrating an example of a first submission table and a second submission table, in accordance with an example embodiment. 
         FIG. 7  is a block diagram illustrating an aggregate function machine learning algorithm component, in accordance with an example embodiment. 
         FIG. 8  is a flow diagram depicting a method for handling confidential data submitted by a user in a computer system, in accordance with an example embodiment. 
         FIG. 9  is a flow diagram depicting a method for handling confidential data submitted by a user in a computer system, in accordance with another example embodiment. 
         FIG. 10  is a block diagram illustrating an intermediate cohort weight learning algorithm component, in accordance with an example embodiment. 
         FIG. 11  is a flow diagram depicting a method for handling confidential data submitted by a user in a computer system, in accordance with another example embodiment. 
         FIG. 12  is a flow diagram illustrating a method of deriving one or more intermediate cohorts, in accordance with a first example embodiment. 
         FIG. 13  is a flow diagram illustrating a method of deriving one or more intermediate cohorts, in accordance with a second example embodiment. 
         FIG. 14  is a flow diagram illustrating a method for handling submission of confidential data, in accordance with an example embodiment. 
         FIGS. 15A-15C  are screen captures illustrating a user interface for displaying insights to a first user from confidential data submitted by other users, in accordance with an example embodiment. 
         FIG. 16  is a diagram illustrating example hierarchies for four different attribute types, in accordance with an example embodiment. 
         FIG. 17  is a block diagram illustrating a cohort score machine learning algorithm component, in accordance with an example embodiment. 
         FIG. 18  is a flow diagram illustrating a method of providing a response to a query on previously submitted confidential data values, in accordance with an example embodiment. 
         FIG. 19  is a block diagram illustrating a representative software architecture, which may be used in conjunction with various hardware architectures herein described. 
         FIG. 20  is a block diagram illustrating components of a machine, according to some example embodiments, able to read instructions from a machine-readable medium (e.g., a machine-readable storage medium) and perform any one or more of the methodologies discussed herein. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure describes, among other things, methods, systems, and computer program products. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the various aspects of different embodiments of the present disclosure. It will be evident, however, to one skilled in the art, that the present disclosure may be practiced without all of the specific details. 
     In an example embodiment, an architecture is provided that gathers confidential information from users, tracks the submission of the confidential information, and maintains and utilizes the confidential information in a secure manner while ensuring that the confidential information is accurate and reliable. 
       FIG. 1  is a block diagram illustrating a confidential data collection, tracking, and usage system  100 , in accordance with an example embodiment. A client device  102  may utilize a confidential data frontend  104  to submit confidential information to a confidential data backend  106 . In some example embodiments, the confidential data backend  106  is located on a server-side or cloud platform  107  while the confidential data frontend  104  is directly connected to or embedded in the client device  102 . However, in some example embodiments, the confidential data frontend  104  is also located on the server-side or cloud platform  107 . 
     There may be various different potential implementations of the confidential data frontend  104 , depending upon the type and configuration of the client device  102 . In an example embodiment, the confidential data frontend  104  may be a web page that is served to a web browser operating on the client device  102 . The web page may include various scripts, such as JavaScript code, in addition to Hypertext Markup Language (HTML) and Cascading Style Sheets (CSS) code designed to perform various tasks that will be described in more detail below. The web page may be served in response to the user selecting a link in a previous communication or web page. For example, the link may be displayed in an email communication to the user, or as part of a feed section of the user&#39;s social networking service member page. This allows the entity operating the confidential data collection, tracking, and usage system  100  to selectively target users to request that they submit confidential information. For example, the entity may determine that there is a need to obtain more salary information for users from Kansas and then may send out communications to, or cause the social networking service to alter feeds of, users in a manner that allows the users to select the link to launch the confidential data frontend  104 . 
     In another example embodiment, the confidential data frontend  104  may be built into an application installed on the client device  102 , such as a standalone application running on a smartphone. Again this confidential data frontend  104  is designed to perform various tasks that will be described in more detail below. 
     One task that the confidential data frontend  104  may be designed to perform is the gathering of confidential data from a user of the client device  102 . Another task that the confidential data frontend  104  may be designed to perform is displaying insights from confidential data contributed by other users. In order to incentivize users to provide certain types of confidential data, in an example embodiment, insights from the confidential data contributed by other users are provided in response to the user contributing his or her own confidential data. As will be described in more detail, a mechanism to ensure that the contribution of confidential data is tracked is provided. 
     Once the confidential data is received from the user, the confidential data frontend  104  may transmit the confidential data along with an identification of the user (such as a member identification reflecting the user&#39;s account with a social networking service) to the confidential data backend  106 . In an example embodiment, this may be performed via, for example, a REST Application Program Interface (API). 
     The confidential data, along with the identification of the user, may be stored in a submission table by the confidential data backend  106  in a confidential information database  108 . In some example embodiments, this submission table may be encrypted in order to ensure security of the information in the submission table. Furthermore, in some example embodiments, the confidential data stored in the submission table may be encrypted using a different key than the identifying information in the submission table. This encryption will be described in more detail below. 
     In another example embodiment, a random transaction number is generated for each confidential data submission. This random transaction number is stored with the identifying information in one table, and then stored with the confidential data in another table, with each table encrypted separately using a different key. In either this example embodiment or the previous example embodiment, encrypting the identifying information separately from the confidential data (either in one table or in separate tables) provides added security against the possibility that a malicious user could gain access to one or the other. In other words, even if a malicious user gained access to the identifying information by, for example, hacking the encryption used to encrypt the identifying information, that would not allow the malicious user to gain access to the confidential data corresponding to the identifying information, and vice versa. In an example embodiment, the encryption mechanism used is one that is non-deterministic, such that the same information encrypted twice would produce different results in each encryption. In another example embodiment, the transaction number itself is also encrypted, thereby preventing even the act of joining separate tables containing the identifying information and the confidential data. 
     In an example embodiment, a submission table may also be able to track when submissions were made by users. As such, the submission table may include additional columns such as, for example, a submission identification, an identification of the user who made the submission, an encryption key for the submission, and timestamp information about when the submission was made. The submission table may then be utilized by the confidential data backend  106  to determine, for example, when to share insights from submissions from other users to a particular user. If, for example, the user has previously submitted confidential data and has done so recently (e.g., within the last year), then the confidential data backend  106  may indicate to the confidential data frontend  104  that it should share insights from confidential data from other users with this particular user. 
     There may be other methods than those described above for determining eligibility of a user for receiving insights from submissions from other users. For example, a predicate expressed in terms of one or more attributes may need to be satisfied in order to receive the insights, such as particular demographic or profile-based attributes. These attributes can include any such attribute, from location, to title, to level of skill, to social networking service activities or status (e.g., about to transition from being an active member to an inactive member), to transactional attributes (e.g., purchased a premium subscription). 
     Additionally, any combination of the above factors can be used to determine whether the user is eligible for receiving insights from submissions from other users. 
     Furthermore, the submission table may also include one or more attributes of the user that made the submission. These attributes may be attributes that can be useful in determining a slice to which the user belongs. Slices will be described in more detail below, but generally involve a segment of users sharing common attributes, such as titles, locations, educational levels, and the like. It should be noted that it is not necessary for these attributes to be stored in the submission table. Since an identification of the user is available in the submission table, it may be possible to retrieve the attributes for the user on an as-needed basis, such as by querying a social networking service with the user identification when needed. 
     A databus listener  110  detects when new confidential data is added to the confidential information database  108  and triggers a workflow to handle the new confidential data. First, the databus listener  110  queries a thresholds data store  116  to determine if one or more thresholds for anonymization have been met. Specifically, until a certain number of data points for confidential data have been met, the confidential data collection, tracking, and usage system  100  will not act upon any particular confidential data data point. As will be described in more detail later, these thresholds may be created on a per-slice basis. Each slice may define a segment of users about which insights may be gathered based on data points from confidential data submitted by users in the slice. For example, one slice may be users with the title “software engineer” located in the “San Francisco Bay Area.” If, for example, the confidential data is compensation information, then it may be determined that in order to gain useful insights into the compensation information for a particular title in a particular region, at least ten data points (e.g., compensation information of ten different users) are needed. In this case, the threshold for “software engineer” located in “San Francisco Bay Area” may be set at ten. The databus listener  110 , therefore, is designed to retrieve the confidential data added to the confidential information database  108 , retrieve the threshold for the slice corresponding to attributes of the user (as stored, for example, in the submission table in the confidential information database  108  or retrieved at runtime from a social networking service), determine if the new data point(s) cause the threshold for the corresponding slice to be exceeded, and, if so, or if the threshold has already been exceeded, insert the data in a backend queue  112  for extract, transform, and load (ETL) functions. 
     In an example embodiment, the thresholds data store  116  contains not just the thresholds themselves but also a running count of how many data points have been received for each slice. In other words, the thresholds data store  116  indicates how close the slice is to having enough data points with which to provide insights. The databus listener  110  may reference these counts when making its determination that a newly submitted data point causes a threshold to be exceeded. Running counts of data points received for each slice are updated in the thresholds data store  116  by the confidential data backend  106 . 
     Since the databus listener  110  only transfers data points for a particular slice to the backend queue  112  once the threshold for that slice has been exceeded, the confidential data data points corresponding to that slice may need to be retrieved from the confidential information database  108  once the threshold is determined to be exceeded. For example, if, as above, the threshold for a particular slice is ten data points, the first nine data points received for that slice may simply be left in the confidential information database  108  and not sent to the backend queue  112 . Then, when the tenth data point for the slice is stored in the confidential information database  108 , the databus listener  110  may determine that the threshold has been exceeded and retrieve all ten data points for the slice from the confidential information database  108  and send them to the backend queue  112  for processing. 
     It should be noted that the information obtained by the databus listener  110  from the confidential information database  108  and placed in the backend queue  112  is anonymized. In an example embodiment, no identification of the users who submitted the confidential data is provided to the backend queue  112 . Indeed, in some example embodiments, the information provided to the backend queue  112  may simply be the confidential data itself and any information needed in order to properly group the confidential data in one or more slices. For example, if slices are designed to group user confidential data based only on user title, location, and years of experience, other attributes for the user that might have been stored in the confidential information database  108 , such as schools attended, may not be transferred to the backend queue  112  when the confidential data tied to those attributes is transferred to the backend queue  112 . This further helps to anonymize the data, as it makes it more difficult for people to be able to deduce the identity of a user based on his or her attributes. 
     It should also be noted that any one piece of confidential data may correspond to multiple different slices, and thus the databus listener  110  may, in some example embodiments, provide the same confidential data to the backend queue  112  multiple times. This can occur at different times as well, because each of the slices may have its own threshold that may be transgressed at different times based on different counts. Thus, for example, compensation data for a user in the “San Francisco Bay Area” with a job title of “software developer” and a school attended as “Stanford University” may be appropriately assigned to one slice of software developers in the San Francisco Bay Area, a slice of Stanford University alums, and a slice of software developers in the United States. All slices may have their own thresholds and counts from confidential data from other users, who may or may not have complete overlap with these three slices. 
     An ETL backend  114  acts to extract, transform, and load the confidential data to anonymize and group it and place it back in the confidential information database  108  in a different location from where it was stored in non-anonymized form. It should be noted that in some example embodiments, the anonymization described above with respect to the databus listener  110  may actually be performed by the ETL backend  114 . For example, the databus listener  110  may send non-anonymized confidential data along with all attributes to the backend queue  112 , and it may be the ETL backend  114  that reviews this data and discards certain elements of it to anonymize it. 
     In an example embodiment, the confidential information is stored in encrypted format in the confidential information database  108  when the databus listener  110  sends it to the backend queue  112 . As such, one function of the ETL backend  114  is to decrypt the confidential information. Encryption and decryption of the confidential data will be discussed in more detail below. 
     The ETL backend  114  writes the anonymized confidential data and slice information into an ETL table corresponding to the slice in the confidential information database  108 . As described earlier, this ETL table may be stored in a different location than the one in which the confidential data was stored initially, such as the submission table described earlier. 
     At a later time, and perhaps using a batch or other periodic process, the information from the ETL table may be loaded in a distributed file system (DFS)  118 . A confidential data relevance workflow  120  may then extract relevant information from the DFS  118  and provide one or more insights into the relevant information in a confidential data insights data store  122 . A confidential data relevance API  124  may then be utilized to provide insights from the confidential data insights data store  122  to the confidential data frontend  104 , which can then display them to a user. As described earlier, these insights may be provided only on a “give-to-get” basis, namely that only users who provide confidential information (and/or have provided it recently) can view insights. 
     Turning now to more detail about the submission process,  FIGS. 2A-2C  are screen captures illustrating an example of a user interface  200  provided by the confidential data frontend  104 , in accordance with an example embodiment. Referring first to  FIG. 2A , the user interface  200  here is depicted as a screen of a standalone application operating on a mobile device, such as a smartphone. In  FIG. 2A , the user is prompted to enter a base salary in a text box  202 , with a drop-down menu providing options for different time periods on which to measure the base salary (e.g., per year, per month, per hour, etc.). Additionally, the user may be identified by name at  204 , the user&#39;s title may be identified at  206 , and the user&#39;s current employer may be identified at  208 . This information may be prepopulated into the user interface  200 , such as by retrieving this information from a member profile for the user in a social networking service. This eliminates the need for the user to enter this information manually, which can have the effect of dissuading some users from providing the confidential information or completing the submission process, especially on a mobile device where typing or otherwise entering information may be cumbersome. 
     Turning to  FIG. 2B , here the user interface  200  displays a number of other possible compensation types  210 - 220  from which the user can select. Selecting one of these other possible compensation types  210 - 220  causes the user interface  200  to provide an additional screen where the user can submit confidential data regarding the selected compensation type  210 - 220 . Here, for example, the user has selected “Stock”  212 . Referring now to  FIG. 2C , the user interface  200  then switches to this screen, which allows the user to provide various specific details about stock compensation, such as restricted stock unit (RSU) compensation  222  and options  224 . The user interface  200  at this stage may also display the other compensation types  210 - 220  that the user can make additional submissions for. 
     Referring back to  FIG. 2B , when the user has completed entering all the confidential data, such as all the different compensation types appropriate for his or her current job, a “Get insights” button  226  may be selected, which launches a process by which the confidential data backend  106  determines whether the user is eligible to receive insights from confidential data from other users and, if so, indicates to the confidential data backend  106  that the insights should be provided. Additionally, selection of the “Get insights” button  226  represents an indication that the submission of the confidential data by this user has been completed, causing the confidential data backend  106  to store the confidential data in the confidential information database  108  as described below, which then may trigger the databus listener  110  to extract the confidential information and cause the ETL backend  114  to anonymize the confidential data and place it in the appropriate ETL tables corresponding to the appropriate slices in which the confidential data belongs. This permits the submitted confidential data to be available for future insights. 
       FIG. 3  is a flow diagram illustrating a method  300  for confidential data collection and storage, in accordance with an example embodiment. In an example embodiment, the method  300  may be performed by the confidential data backend  106  of  FIG. 1 . At operation  302 , confidential data is obtained. At operation  304 , an identification of the user who submitted the confidential data is obtained. It should be noted that while operations  302  and  304  are listed separately, in some example embodiments they may be performed in the same operation. For example, in an example embodiment, the confidential data frontend  104  may, upon receiving an indication from a user that input of confidential data in the confidential data frontend  104  by the user has been completed, forward the inputted confidential data and an identification of the user to the confidential data backend  106 . In other example embodiments, however, the operations  302  and  304  may be performed separately. For example, in an example embodiment, the identification of the user may not be obtained directly from the confidential data frontend  104 , but rather some other type of identifying information may be obtained directly from the confidential data frontend  104 , and this other type of identifying information may be used to query a social networking service or other third-party service for the identification information for the user. Regardless, after operations  302  and  304  have been performed, the confidential data backend  106  has at its disposal some confidential data and identification information for the user who entered the confidential data. 
     It should be noted that the confidential data may be a single piece of information, or may be multiple related pieces of information. For example, the confidential data may simply include a total compensation value and nothing more, or may include a complete breakdown of different types of compensation (e.g., base salary, bonus, stock, etc.). 
     Users are understandably concerned about the security of the confidential information, and specifically about a malicious user being able to correlate the confidential information and the identification of the user (i.e., not just learning the confidential information but tying the confidential information specifically to the user). As such, at operation  306 , the confidential data is encrypted using a first key and stored in a first column of a submission table in a confidential information database. Then, at operation  308 , the identification of the user who submitted the confidential data is separately encrypted using a second key and stored in a second column of the submission table in the confidential information database. 
     Additionally, a number of optional pieces of information may, in some example embodiments, be stored in the submission table at this point. At operation  310 , a timestamp of the submission of the confidential data may be stored in a column in the submission table. This timestamp may be used in, for example, a determination of whether the user is eligible to receive insights from confidential data submitted by other users. At operation  312 , one or more attributes of the user may be stored as one or more columns in the submission table. These attributes may be used, for example, in determining to which slice(s) the confidential data may apply, as will be described in more detail below. 
       FIG. 4  is a diagram illustrating an example of a submission table  400 , in accordance with an example embodiment. Each row in the submission table  400  corresponds to a different submission. Here, the submission table  400  includes five columns. In a first column  402 , confidential data encrypted by a first key is stored. In a second column  404 , identification of the user who submitted the corresponding confidential data, encrypted by a second key, is stored. In a third column  406 , a timestamp for the submission is stored. In a fourth column  408 , a first attribute of the user, here location, is stored. In a fifth column  410 , a second attribute of the user, here title, is stored. Of course, there may be additional columns to store additional attributes or other pieces of information related to the submission. 
     Notably,  FIG. 4  depicts an example embodiment where only the first and second columns  402 ,  404  are encrypted, using different encryption keys. In some example embodiments, the additional columns  406 - 410  may also be encrypted, either individually or together. In some example embodiments, one or more of these additional columns  406 - 410  may be encrypted using the same key as the first or second column  402 ,  404 . Furthermore, in some example embodiments, the submission table  400  may be additionally encrypted as a whole, using a third encryption key different from the keys used to encrypt the first and second columns  402 ,  404 . 
     It should be noted that while  FIGS. 3 and 4  describe the confidential data as being stored in a single column in a submission table, in some example embodiments, this column is actually multiple columns, or multiple sub-columns, with each corresponding to a subset of the confidential data. For example, if the confidential data is compensation information, the confidential data may actually comprise multiple different pieces of compensation information, such as base salary, bonus, stock, tips, and the like. Each of these pieces of compensation information may, in some example embodiments, have its own column in the submission table. Nevertheless, the processes described herein with regard to the “column” in which the confidential data is stored apply equally to the embodiments where multiple columns are used (e.g., the individual pieces of compensation information are still encrypted separately from the user identification information). 
       FIG. 5  is a flow diagram illustrating a method  500  for confidential data collection and storage, in accordance with an example embodiment. In contrast with  FIG. 3 ,  FIG. 5  represents an example embodiment where the confidential data and the identification of the user who submitted the confidential data are stored in separate tables in order to provide additional security. At operation  502 , confidential data is obtained. At operation  504 , an identification of the user who submitted the confidential data is obtained. As in  FIG. 3 , while operations  502  and  504  are listed separately, in some example embodiments they may be performed in the same operation. 
     At operation  506 , a transaction identification is generated. This transaction identification may be, for example, a randomly generated number or character sequence that uniquely identifies the submission. At operation  508 , the transaction identification may be encrypted using a first key. At operation  510 , the transaction information (either encrypted or not, depending upon whether operation  508  was utilized) is stored in a first column in a first submission table and in a first column in a second submission table in a confidential information database. 
     At operation  512 , the confidential data is encrypted using a second key and stored in a second column of the first submission table in the confidential information database. Then, at operation  514 , the identification of the user who submitted the confidential data is separately encrypted using a third key and stored in a second column of the second submission table in the confidential information database. 
     Additionally, as in  FIG. 3 , a number of optional pieces of information may, in some example embodiments, be stored in the first and/or second submission tables at this point. At operation  516 , a timestamp of the submission of the confidential data may be stored in a column in the second submission table. This timestamp may be used in, for example, a determination of whether the user is eligible to receive insights from confidential data submitted by other users. At operation  518 , one or more attributes of the user may be stored as one or more columns in the second submission table. These attributes may be used, for example, in determining to which slice(s) the confidential data may apply, as will be described in more detail below. It should be noted that while operations  516  and  518  are described as placing information in the second submission table, in other example embodiments, one or more of these pieces of information may be stored in the first submission table. 
     If operation  508  is utilized, then the fact that the transaction identification is encrypted and is the only mechanism by which to link the confidential data in the first submission table with the user identification in the second submission table through a join operation provides an additional layer of security. 
       FIG. 6  is a diagram illustrating an example of a first submission table  600  and a second submission table  602 , in accordance with an example embodiment. Each row in each of the first and second submission tables  600 ,  602  corresponds to a different submission. Here, the first submission table  600  includes two columns. In a first column  604 , transaction identification information encrypted by a first key is stored. In a second column  606 , confidential data encrypted by a second key is stored. 
     The second submission table  602  includes five columns. In a first column  608 , transaction identification information encrypted by the first key is stored. In a second column  610 , identification of the user who submitted the corresponding confidential data, encrypted by a third key, is stored. In a third column  612 , a timestamp for the submission is stored. In a fourth column  614 , a first attribute of the user (here location) is stored. In a fifth column  616 , a second attribute of the user, here title, is stored. Of course, there may be additional columns to store additional attributes or other pieces of information related to the submission. 
     Notably,  FIG. 6  depicts an example embodiment where only the first and second columns  608 ,  610  of the second submission table  602  are encrypted, using different encryption keys. In some example embodiments, the additional columns  612 - 616  may also be encrypted, either individually or together. Furthermore, in some example embodiments, the first and/or second submission tables  600 ,  602  may be additionally encrypted as a whole, using an additional encryption key(s) different from the keys described previously. 
     It should be noted that while  FIGS. 5 and 6  describe the confidential data as being stored in a single column in a first submission table, in some example embodiments this column is actually multiple columns, or multiple sub-columns, with each corresponding to a subset of the confidential data. For example, if the confidential data is compensation information, the confidential data may actually comprise multiple different pieces of compensation information, such as base salary, bonus, stock, tips, and the like. Each of these pieces of compensation information may, in some example embodiments, have its own column in the first submission table. Nevertheless, the processes described herein with regard to the “column” in which the confidential data is stored apply equally to the embodiments where multiple columns are used (e.g., the individual pieces of compensation information are still encrypted separately from the user identification information). 
     Since insights from submitted confidential data will be generated and shared with users who submit confidential data, there is a concern that the submitted confidential data upon which the insights are based is reliable. Inaccuracies in the submitted confidential data, whether caused by user error, maliciousness, or system errors, could potentially cause the insights to be skewed. As such, in an example embodiment, computer operations are undertaken in order to remove or correct such incorrect confidential data after submission. 
     In an example embodiment, the computer operations undertaken include detection of outliers in the submitted confidential data. Outliers include any piece of submitted data that appears, after one or more analyses described below, to be out of place or incorrect. Then, one or more actions may be taken on these outliers, including, for example, removal of the outliers from the insights, requesting user resubmission or “double-checking” of the confidential data corresponding to the outliers, and the like. 
     In an example embodiment, outlier detection is based on one or more external data sets. These external data sets may have statistical information about confidential information that is relevant to determining whether submitted confidential information is an outlier or not. For example, in the case where the confidential information is compensation information, external data sets from, for example, the Bureau of Labor Statistics, employment agencies, employer surveys, and the like might provide information such as average compensation in particular fields, job titles in particular regions, or even more detailed statistical information such as compensation percentiles. 
     However, the external data sets are likely to follow a different taxonomy of professions and geographic divisions as compared to the data of the professional social networking service. 
     A taxonomy is a classification scheme. In the context of job titles, a job title taxonomy is a complete set of possible job titles used by an entity (e.g., the social networking service or an external entity that manages or creates the external data set). Each job description provided by a user of a social networking service is mapped to a job title in the job title taxonomy. Similarly, a taxonomy is used for location(s). For example, one entity can have a taxonomy of locations that includes zip codes, while another entity can include a taxonomy of locations that includes states, cities, counties, neighborhoods, or the like. Harmonizing data from disparate taxonomies can be challenging. 
     Consider a taxonomy that breaks location into zip codes and a taxonomy that breaks location into cities and greater metropolitan areas. If the city or greater metropolitan area spans multiple zip codes or does not span an entire zip code, it is difficult to determine which city or greater metropolitan area a zip code corresponds to or vice versa. In an example embodiment, the external data sets are utilized by generating mappings from the external taxonomy (a taxonomy of the external data) to internal taxonomies (a taxonomy of, for example, the social network data). The underlying mappings can be based on population and/or member demographic information for mapping regions and titles. 
     Percentiles in the external data set show the confidential data values for various percentiles of the overall data set. For example, the external data set may show that the 10th percentile of factory workers (the compensation that 10% of factory workers fall below) make $15,000 a year on average, while those in the 25th percentile (the compensation that 25% of factory workers fall below) make $25,000 a year on average, and so on. 
     In an example embodiment, one or more external data sets are used to calculate initial upper and lower limits on values for the confidential data for particular combinations of member attributes. Thus, for example, an upper and lower limit for base salary of software engineers in the San Francisco Bay Area may be calculated. In an example embodiment, the Box and Whisker method is utilized in making this calculation. Specifically, an interquartile range value is calculated by subtracting the value in the external data set for the member attribute combination for the 25th percentile from the value for the 75th percentile. Thus, for example, if the external data set indicates that 25% of software engineers in the San Francisco Bay Area make less than $105,000, while 75% of software engineers in the San Francisco Bay Area make less than $175,000, then the interquartile range for software engineers in the San Francisco Bay Area is $175,000−$105,000=$70,000. 
     An initial lower limit is then established by calculating the following formula:
 
Initial lower limit=max(0,25 th  percentile−alphaLower*interQuartileRange).
 
     An initial upper limit is then established by calculating the following formula:
 
Initial upper limit=75 th  percentile+alphaUpper*interQuartileRange.
 
     In these formulas, alphaLower and alphaUpper are multiplicative parameters. In an example embodiment, values for these parameters are selected based on experimentation. In some example embodiments, the values for these parameters may be the same across all industries, regions, or other attributes, but in other example embodiments the values may vary based on attribute. For example, there may be one value for the alphaLower parameter for Tech workers and a different value for the alphaLower parameter for Factory workers. 
     In an example embodiment, one or more extrapolation techniques are used to calculate values for percentiles not specified in the external data set. In an example embodiment, linear or spline interpolation is used as one of these extrapolation techniques. For example, with linear interpolation, the following formulas may be computed:
 
 pct \alphaExtrapolated= pct 10*(25−\alpha)/(25−10)+ pct 25*(\alpha−10)/(25−10), where \alpha=−10,0,etc.
 
\ pct \betaExtrapolated= pct 90*(\beta−75)/(90−75)+ pct 75*(90−\beta)/(90−75), where \beta=100,110,etc.
 
     The idea behind the above formulas is that values for outlier percentiles, such as the 0th percentile or −10th percentile, can be determined via interpolation, based on the values for the nearest two percentiles. Thus, the value for the 0th percentile may be calculated based on the values for the 10th and 25th percentiles, while the value for the 100th percentile may be calculated based on the values for the 90th and 75th percentiles. 
     Notably, the above calculations can be performed for each combination of attributes specified in the external data set by the same super-attributes. Specifically, the external data set may specify values on a more granular level than the member attributes for the member who submitted the confidential information that needs to be examined to determine if it is an outlier. For example, a member with the attributes “Computer Programmer” and “San Francisco Bay Area” may submit compensation information, but the Bureau of Labor Statistics may break down percentiles of compensation information based on city (e.g., Santa Clara, San Jose, etc.) and not region, and may also break down percentiles of compensation information based on specific job title (e.g., Software Product Manager, Coder, etc.) rather than on super-title or field (e.g., Computer Programmer). Thus, the above calculations may be performed for all the values in the external data set that come under the umbrella of the member attributes. The calculated values for initial lower limit, initial upper limit, pct\alphaExtrapolated, and pct\betaExtrapolated may be computed for each of the percentile ranges for the Software Product Manager/Santa Clara, Coder/Santa Clara, Software Product Manager/San Jose, and Coder/San Jose combinations (as well as any other combinations that would fall under the category of “Computer Programmer” and “San Francisco Bay Area”), and then these values may be aggregated. 
     At this point, a merged lower limit and merged upper limit may be computed as follows: 
     mergedLowerLimitExternalData=max(minWage, aggregateFuncLower(boxAndWhiskerLowerLimitAggregated, pct\alphaExtrapolatedAggregated)), where aggregateFuncLower could be chosen to be max, min, etc., boxAndWhiskerLowerLimitAggregated is the lower limit computed by the Box and Whisker method aggregated over the segments, and pct\alphaExtrapolatedAggregated is the pct/alphaExtrapolated values aggregated over the segments. 
     mergedUpperLimitExternalData=aggregateFuncUpper(boxAndWhiskerUpperLimitAggregated, pct\betaExtrapolatedAggregated), where aggregateFuncUpper could be chosen to be max, min, etc., boxAndWhiskerUpperLimitAggregated is the upper limit computed by the Box and Whisker method aggregated over the segments, and pct\betaExtrapolatedAggregated is the pct/betaExtrapolated values aggregated over the segments. 
     It should be noted that in some example embodiments the aggregateFuncLower and/or aggregateFuncUpper could be computed based on more than the two values specified, but could also include some sort of“hard limit.” The main example of such a hard limit would be the federal minimum wage, which could be used to calculate a minimum compensation for a full-time worker, and this minimum compensation may be used as a floor for the mergedLowerLimitExternalData, such that even if the boxAndWhiskerLowerLimitAggregated and/or pct\alphaExtrapolatedAggregated are below this floor, the values below this floor will always be seen as outliers. This is reflected in the formulas above. 
     Additionally, while minimum and maximum are provided as example functions for aggregateFuncLower and aggregateFuncUpper, other functions, such as averages and weighted averages, could alternatively be used. The weights for the weighted average may be altered over time via machine learning algorithms. Additionally, the parameters used for the other calculations described above could also be learned via machine learning algorithms. 
       FIG. 7  is a block diagram illustrating an aggregate function machine learning algorithm component  700 , in accordance with an example embodiment. In some example embodiments, the aggregate function machine learning algorithm component  700  may be located on the confidential data backend  106 . 
     In a training component  702 , sample segment information  704  from sample segment data is fed to a feature extractor  706 , which acts to extract curated features  708  from the sample segment information  704 . 
     Thus, for example, the feature extractor  706  may extract features such as segment attributes (e.g., location, title, etc.) from the sample segment information  704 . Extraction may be performed via a number of different extraction techniques. In an example embodiment, the attributes may be directly extracted from the sample segment information  704 . In other example embodiments, more complex transformations and/or pre-processing may be performed, such as mapping of the segment attributes to social network attribute taxonomy categories. 
     The curated features  708  may be fed to a machine learning algorithm  710  along with known valid ranges for confidential data  712  for each of the segments in the sample segment information  704 . The machine learning algorithm  710  then trains an aggregate function model  714  based on the curated features  708  and known valid ranges for confidential data  712 . The machine learning algorithm  710  may be selected from among many different potential supervised or unsupervised machine learning algorithms. Examples of supervised machine learning algorithms include artificial neural networks, Bayesian networks, instance-based learning, support vector machines, random forests, linear classifiers, quadratic classifiers, k-nearest neighbor, decision trees, and hidden Markov models. Examples of unsupervised machine learning algorithms include expectation-maximization algorithms, vector quantization, and information bottleneck method. In an example embodiment, a binary logistic regression model is used. Binary logistic regression deals with situations in which the observed outcome for a dependent variable can have only two possible types. Logistic regression is used to predict the odds of one case or the other being true based on values of independent variables (predictors). 
     Specifically, the aggregate function model  714  may be trained to output parameters used in the outlier detection techniques described above and below, specifically, for example, initial upper limits and initial lower limits. Other parameters, such as alphaUpper and alphaLower parameters, and weights for the aggregation functions, may also be output by the aggregate function model  714 . 
     In a prediction component  716 , a candidate segment  718  is fed to a feature extractor  720 , which acts to extract curated features  722  from the candidate segment  718 . The curated features  722  are then used as input to the trained aggregate function model  714 , which outputs parameters used for the outlier detection. 
     It should be noted that while the feature extractor  706  and the feature extractor  720  are depicted as separate components, they may be the same component in some example embodiments. Additionally, a large number of different types of features could be extracted using the feature extractors  706  and  720 . Furthermore, while in an example embodiment the features extracted by the feature extractor  706  are the same as the features extracted by the feature extractor  720 , in other example embodiments there may be differences in the features. 
       FIG. 8  is a flow diagram depicting a method  800  for handling confidential data submitted by a user in a computer system, in accordance with an example embodiment. The method  800  may be performed at, for example, the confidential data relevance workflow  120  of  FIG. 1 . 
     At operation  802 , a submission of confidential data of a first confidential data type is received from a first user via a first computerized user interface. At operation  804 , one or more attributes of the first user are determined. This determination may be based on attributes that are commonly used by third-party data sources to segregate statistical data gathered about confidential data. For example, third-party data sources often segregate gathered data on compensation based on job title or industry and location. Therefore, in some example embodiments, the one or more attributes may include job title and location. It should be noted that due to the hierarchical nature of many of these types of attributes, it may be common for the statistical data to be segregated at a more granular level than the one or more attributes, or at least at a level which the one or more attributes may be generalized to. As was described earlier, such instances can be compensated for later in the method  800  through aggregation. Therefore, at operation  804 , the one or more attributes of the first user may be determined at a level at which information is available. One common source for attribute information for the first user may be a member profile in a social networking service, where such attributes may be explicitly listed. However, it is not necessary that the attribute information be retrieved from a member profile, or even that the attribute information be explicitly listed (e.g., it can be inferred as well). 
     At operation  806 , a plurality of segments of percentile information indicating values for confidential data of the first confidential data type for a plurality of users matching the one or more attributes of the first user are retrieved from an external data source. For purposes of this disclosure, “matching” shall be interpreted as meaning that the segment is relevant to the one or more attributes of the first user. This may mean that the segment has been segregated based on one of the attributes itself, or based on a sub-attribute of the attribute. For example, the first user may have a job title of “Computer Programmer” and a location of “San Francisco Bay Area,” and thus segments including “Software Product Manager”/“San Jose” and “Software Product Manager”/“Santa Clara” may both be considered matches (assuming “Software Product Manager” is a sub-attribute of “Computer Programmer” in the title taxonomy), but segments including “Software Product Manager”/“Los Angeles” and even “Computer Programmer”/“New York” may not be considered matches. Additionally, segments segregated at a higher attribute level in the taxonomy may also be considered a match, such as a segment including “Software Product Manager”/“California,” since California contains the San Francisco Bay Area and is therefore a super-attribute in the taxonomy. 
     Furthermore, segments that have not been segregated at all along the taxonomy of one of the attributes may also be considered a match. For example, if the segment is for “Software Product Manager” but no location is specified, the segment still may be considered a match. 
     Thus, each of the plurality of segments includes values, for a different combination of attributes of the plurality of users, for data of the first confidential data type for each of a plurality of percentiles. 
     A loop is then begun for each of the segments. At operation  808 , an interquartile range for a first and a second of the plurality of percentiles in the segment is calculated, wherein the value for the first of the plurality of percentiles is lower than the value for the second of the plurality of percentiles. Then, at operation  810 , an initial lower limit for the segment is computed by taking a maximum of zero or the difference between the value for the first of the plurality of percentiles and a product of a preset alpha parameter and the interquartile range. At operation  812 , an initial upper limit is computed for the segment by adding the value for the second of the plurality of percentiles to a product of a preset beta parameter and the interquartile range. 
     At operation  814 , interpolation is performed on the values for the plurality of percentiles for the segment to obtain values for a third percentile. At operation  816 , interpolation is performed on the values for the plurality of percentiles for the segment to obtain values for a fourth percentile. In both operations  814  and  816 , this interpolation may be, for example, based on linear interpolation or spline interpolation. The third percentile may have a lower value that any percentile in the plurality of percentiles, and the fourth percentile may have a higher value than any percentile in the plurality of percentiles. Furthermore, in some example embodiments, the third percentile is below zero percent and/or the fourth percentile is above one hundred percent. 
     At operation  818 , it is determined if there are any more segments. If so, then the method  800  loops back to operation  808  for the next segment in the plurality of segments. If not, then at operation  820  the initial lower limits and the interpolated values for the third percentile are aggregated across the segments. Then, at operation  822 , the initial upper limits and the interpolated values for the fourth percentile are aggregated across the segments. 
     At operation  824 , a merged lower limit is determined by applying a function to the aggregated initial lower limit and aggregated interpolated values for the third percentile. At operation  826 , a merged upper limit is determined by applying a function to the aggregated initial upper limit and aggregated interpolated values for the fourth percentile. 
     At operation  828 , it is determined whether the confidential data value submitted by the first user is an outlier by determining if the confidential data value submitted by the first user is lower than the merged lower limit or higher than the merged upper limit. At operation  830 , in response to a determination that the confidential data value submitted by the first user is an outlier, the confidential data value submitted by the first user is prevented from being used for insights provided to other users. This prevention may take many forms, including, for example, removing the submitted confidential data value from the DFS  118 , or simply not providing insights into the confidential data insights data store  122  using that particular submitted confidential data value. 
     There may be some limitations to using external data sets to detect outliers, however. One limitation is that typically the external data sets are limited to just one particular type of confidential data. For example, the Bureau of Labor Statistics may keep percentiles reflecting base salary, but not bonuses, stock compensation, or the like, or may simply keep percentiles reflecting overall compensation, without breaking it down into the types of compensation. Additionally, in some cases the mapping between the taxonomies of the external data set and the social networking service may be noisy, making the derived limits unreliable. Furthermore, there may be some segments that lack data; for example, certain titles and/or locations may not be tracked. In such cases, it may be desirable to perform outlier detection based on information from other members of the social networking service rather than an external data set. 
     In an example embodiment, grouped internal confidential data (e.g., confidential data gathered through user submission to a social networking service) is used to calculate initial upper and lower limits on values for the confidential data for particular combinations of member attributes. Thus, for example, an upper and lower limit for base salary of software engineers in the San Francisco Bay Area may be calculated. 
     Specifically, the internal confidential data is grouped based on cohort. Each cohort c represents a grouping of data pertaining to a particular combination of user attributes for users who submitted the confidential data. Thus, for example, a cohort may be for a particular title and region combination, such as “Computer Programmer” and “San Francisco Bay Area,” or a particular title, company, and region combination, such as “Computer Programmer,” “XYZ Corp.” and “San Francisco Bay Area.” A first step then involves obtaining the set E(c) of all submitted entries for that cohort. Each element of E(c) is an ordered r-tuple of confidential data values, where r is the number of types for the data. For example, if the confidential data is compensation information, the types may include base salary, bonus, stock, tips, etc. Data for some of the types may be missing. For example, while some users may submit base salary, bonus, and stock (and not tips), others may submit base salary and tips (and not bonus or stock). For each individual confidential data type t, let E(c, t) denote the set of submitted values that are non-null for cohort c. 
     Data from E(c, t) for each matching cohort c may then be aggregated to create percentiles based on the submitted data values. In an example embodiment, the 25th, 50th, and 75th percentiles may be computed. 
     For each matching cohort, an initial lower and upper limit may then be calculated. In an example embodiment, Box and Whisker method is utilized in making this calculation. Specifically, an interquartile range value is calculated by subtracting the value in the data set for the member attribute combination for the 25th percentile from the value for the 75th percentile. 
     An initial lower limit is then established by calculating the following formula:
 
Initial lower limit=max(0,25 th  percentile−alphaLower*interQuartileRange).
 
     An initial upper limit is then established by calculating the following formula:
 
Initial upper limit=75 th  percentile+alphaUpper*interQuartileRange.
 
     In these formulas, alphaLower and alphaUpper are multiplicative parameters. In an example embodiment, values for these parameters are selected based on experimentation. In some example embodiments, the values for these parameters may be the same across all industries, regions, or other attributes, but in other example embodiments the values may vary based on attribute. For example, there may be one value for the alphaLower parameter for Tech workers and a different value for the alphaLower parameter for Factory workers. 
     The lower limit may then be set based on the calculated initial lower limit. Certain types of confidential data have an alternative lower limit, which may be higher than the initial lower limit. For example, base salary may be a confidential data type that has an alternative lower limit equal to the annualized federal minimum wage. If that annualized federal minimum wage is higher than the calculated initial lower limit, then the annualized federal minimum wage may be taken as the final lower limit for the cohort/compensation type combination. Otherwise, the initial lower limit may be taken as the final lower limit for the cohort/compensation type combination. Likewise, certain confidential data types may have an alternative upper limit, which may be greater than the initial upper limit. 
     Once the final lower and upper limits are determined, then user-submitted values may be removed or clipped based on these limits. How this removal or clipping occurs may differ based on the confidential data type in which the outlier lies. For example, if the outlier lies in the base salary submitted by a member of cohort c, then the entire r-tuple entry may be removed as an outlier. For other compensation types, however, such as bonus, data may be removed or clipped according to different rules. As an example, the rules may specify that a null entry is retained as-is, a non-null entry below the final lower limit is set to the final lower limit, and a non-null entry above the final upper limit is set to the final upper limit. 
     In an example embodiment, the parameters used in the above outlier calculations may be set using one or more machine-learning algorithms. These machine-learning algorithms may operate, for example, in the manner described above with respect to  FIG. 7 . 
       FIG. 9  is a flow diagram depicting a method  900  for handling confidential data submitted by a user in a computer system, in accordance with another example embodiment. The method  900  may be performed at, for example, the confidential data relevance workflow  120  of  FIG. 1 . 
     At operation  902 , a submission of confidential data of a first confidential data type is received from a first user via a first computerized user interface. In an example embodiment, this submission may take the form of an r-tuple, as described above. At operation  904 , one or more attributes of the first user are determined. The one or more attributes of the first user may be determined at a level at which information is available. One common source for attribute information for the first user may be a member profile in a social networking service, where such attributes may be explicitly listed. However, it is not necessary that the attribute information be retrieved from a member profile, or even that the attribute information be explicitly listed (e.g., it can be inferred as well). 
     At operation  906 , one or more cohorts corresponding to the one or more attributes are identified. These cohorts are various combinations of the one or more attributes for which there exist submitted member confidential data values in a database, such as in the DFS  118 . The decision as to whether or not a cohort corresponds to the one or more attributes may, in some example embodiments, be similar to the decision as to whether a segment of an external data set “matches” one or more attributes, as described above. Specifically, it shall be interpreted as meaning that the cohort is relevant to the one or more attributes of the first user. This may mean that the cohort is grouped based on one of the attributes itself, or based on a sub-attribute of the attribute. For example, the first user may have a job title of “Computer Programmer” and a location of “San Francisco Bay Area,” and thus cohorts including “Software Product Manager”/“San Jose” and “Software Product Manager”/“Santa Clara” may both be considered matches (assuming “Software Product Manager” is a sub-attribute of “Computer Programmer” in the title taxonomy), but cohorts including “Software Product Manager”/“Los Angeles” and even “Computer Programmer”/“New York” may not be considered matches. Additionally, cohorts segregated at a higher attribute level in the taxonomy may also be considered a match, such as a cohort including “Software Product Manager”/“California,” since California contains the San Francisco Bay Area and is therefore a super-attribute in the taxonomy. 
     Furthermore, cohorts that have not been segregated at all along the taxonomy of one of the attributes may also be considered a match. For example, if the cohort is for “Software Product Manager” but no location is specified, the cohort still may be considered a match. 
     At operation  908 , a plurality of tuples in the cohorts may be analyzed to compile percentile information for each confidential data type in each tuple. A loop may then be begun for each confidential data type in the cohort. 
     At operation  910 , an interquartile range for a first and a second of the plurality of percentiles in the percentile information for the confidential data type in this cohort is calculated, wherein the value for the first of the plurality of percentiles is lower than the value for the second of the plurality of percentiles. Then, at operation  912 , an initial lower limit for the confidential data type and cohort is computed by taking a maximum of zero or the difference between the value for the first of the plurality of percentiles and a product of a preset alpha parameter and the interquartile range. At operation  914 , an upper limit is computed for the confidential data type and cohort by adding the value for the second of the plurality of percentiles to a product of a preset beta parameter and the interquartile range. 
     At operation  916 , a final lower limit may be set as the maximum of a predetermined floor (e.g., annualized federal minimum wage for base salary) for the confidential data type, if any, and the initial lower limit. For all other confidential data types, the final lower and upper limits may simply be set as the initial lower and upper limits, respectively. 
     At operation  918 , it is determined if there are any more confidential data types in the cohort. If so, then the method  900  loops back to operation  910 . 
     If not, then at operation  920 , it is determined whether the confidential data value submitted by the first user is an outlier by determining if the confidential data value submitted by the first user is lower than the final lower limit or higher than the final upper limit. If so, then at operation  922 , it is determined whether the confidential data value is of a type that necessitates removal of the entire r-tuple, such as if the outlier confidential data type is base salary. If so, then at operation  924 , the entire r-tuple is removed. “Removed” means removed from inclusion in insights provided to users, although in some cases this removal may include purging the r-tuple completely. If at operation  922  it is determined that the confidential data value is not of a type that necessitates removal of the entire r-tuple, then at operation  926  it is determined whether the submitted confidential data value is null. If so, then at operation  928  the confidential data value is retained as-is. 
     If not, then at operation  930  it is determined whether the submitted confidential data value is below the final lower limit for that confidential data value type in the cohort of the user who submitted it. If so, then at operation  932  the confidential data value is set to the final lower limit. If not, then at operation  934  it is determined if the submitted confidential data value is above the upper limit for that confidential data value type in the cohort of the user who submitted it. If so, then at operation  936  the confidential data value is set to the upper limit. 
     In another example embodiment, rather than, or in conjunction with, detecting outliers based on percentiles (from external or internal data sets, as described above), submitted confidential data is compared to how well it fits to a designed distribution. First, multiple confidential data submissions are grouped into cohorts at a generalized level to determine an empirical probability distribution. This may involve removing one of the attributes of the initial cohort of grouped confidential data submissions or moving one or more attributes of the initial cohort up one level in a hierarchy. For example, if an initial cohort of submitted data includes a tuple including title, company, and region as attributes, then this cohort may be generalized to title and region. If the initial cohort includes a tuple including title and city, then this cohort may be generalized to title and region, or title and state, or title and country. If the initial cohort includes a tuple including title and region, then this cohort may be generalized to function and region. 
     It should be noted that this generalization may be based on the number of data points (submitted confidential data) in the cohort and involves an attempt to increase the number of data points in the cohort beyond a predetermined threshold. As such, it is possible that the initial cohort already has more data points than the predetermined threshold and thus no generalization is necessary. If that is not the case, however, then a systematic algorithm for finding a generalized version of the cohort that does have more data points than the predetermined threshold may be followed. This algorithm may involve attempting to remove each attribute of the initial cohort to form intermediate cohorts and measuring the number of data points in each intermediate cohort. Likewise, each attribute of the initial cohort is generalized up one level in a hierarchy to form additional intermediate cohorts and the number of data points in each of these intermediate cohorts is also measured. The intermediate cohort with the greatest number of data points is then selected and the number of data points in the selected intermediate cohort is compared with the predetermined threshold. If the number of data points in the selected intermediate cohort exceeds the predetermined threshold, then the selected intermediate cohort is selected as the final cohort. If not, however, the algorithm repeats for the selected intermediate cohort, generalizing its attributes by removing each and moving each up one level to form another set of intermediate cohorts, and then comparing the number of data points in this other set of intermediate cohorts to the predetermined threshold. The process repeats until an intermediate cohort is found with more data points than the predetermined threshold, and such an intermediate cohort is selected as the final cohort. 
     In another example embodiment, rather than selecting a single cohort as the final cohort to use in calculating upper and lower limits, two or more of the intermediate cohorts are selected and, as will be described in more detail below, the upper and lower limits are calculated based on a weighted average of upper and lower limits calculated from the two or more intermediate cohorts. The weights may be dynamically learned based on a machine learning model. 
       FIG. 10  is a block diagram illustrating an intermediate cohort weight learning algorithm component  1000 , in accordance with an example embodiment. In some example embodiments, the intermediate cohort weight learning algorithm component  1000  may be located on the confidential data backend  106 . 
     In a training component  1002 , sample intermediate cohorts  1004  are fed to a feature extractor  1006 , which acts to extract curated features  1008  from the sample intermediate cohorts  1004 . 
     Thus, for example, the feature extractor  1006  may extract features such as the upper and lower limits from the sample intermediate cohorts  1004 . The curated features  1008  may be fed to a machine learning algorithm  1010  along with ground truth information  1012  for each of the sample intermediate cohorts  1004 . The ground truth would consist of valid and invalid compensation entries for each of one or more cohorts. Then, for each cohort, sample intermediate cohorts and the associated limits are computed, and the weights for intermediate cohorts are learned using a machine learning algorithm that attempts to preserve valid compensation entries and prune invalid compensation entries. The machine learning algorithm  1010  then trains an intermediate cohort weight model  1014  based on the curated features  1008  and ground truth information  1012 . The machine learning algorithm  1010  may be selected from among many different potential supervised or unsupervised machine learning algorithms. Examples of supervised machine learning algorithms include artificial neural networks, Bayesian networks, instance-based learning, support vector machines, random forests, linear classifiers, quadratic classifiers, k-nearest neighbor, decision trees, and hidden Markov models. Examples of unsupervised machine learning algorithms include expectation-maximization algorithms, vector quantization, and information bottleneck method. In an example embodiment, a binary logistic regression model is used. Binary logistic regression deals with situations in which the observed outcome for a dependent variable can have only two possible types. Logistic regression is used to predict the odds of one case or the other being true based on values of independent variables (predictors). 
     Specifically, the intermediate cohort weight model  1014  may be trained to output weights to intermediate cohorts. 
     In a prediction component  1016 , a candidate intermediate cohort  1018  is fed to a feature extractor  1020 , which acts to extract curated features  1022  from the candidate intermediate cohort  1018 . The curated features  1022  are then used as input to the trained intermediate cohort weight model  1014 , which outputs a weight for each submitted candidate intermediate cohort  1018 . 
     It should be noted that while the feature extractor  1006  and the feature extractor  1020  are depicted as separate components, they may be the same component in some example embodiments. Additionally, a large number of different types of features could be extracted using the feature extractors  1006  and  1020 . Furthermore, while in an example embodiment the features extracted by the feature extractor  1006  are the same as the features extracted by the feature extractor  1020 , in other example embodiments there may be differences in the features. 
     In some example embodiments, the intermediate cohorts included in the weighted average include all possible generalizations of the initial cohort, albeit with some of the weights assigned, perhaps making the contribution of some of the more error-prone generalizations negligible. In other example embodiments, some sort of threshold is used to determine whether or not to include an intermediate cohort in the weighted average, such as the total number of data points in each cohort, as described above, or a calculated error value for the cohort with respect to a fitted parameterized distribution. 
     Once the final cohort(s) are selected in accordance with one of the methods described above, a parameterized distribution is then fitted to the data points in the final cohort. In an example embodiment, the parameterized distribution is a Johnson distribution. Fitting data with a Johnson distribution involves transforming a continuous random variable x, whose distribution is unknown, into a standard normal (z) with mean zero and variance of one, according to one of four normalizing translations. 
     The general form of the translation is 
     
       
         
           
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     where f′(y)=df/dy. There are four methods to estimate Johnson parameters (γ, δ, ξ, λ), namely moment matching, percentile matching, least squares, and minimum Lp norm estimation. The moment matching method involves determining the family distribution first by the location of skewness β1 and kurtosis β2. The number of parameters to be estimated is then determined by solving a system of non-linear equations between the sample moments and the corresponding moments of the fitted distribution. Briefly, this involves the following:
         1. Calculate the moments of x: m2, m3, and m4.   2. Calculate the skewness and kurtosis of x: β1≡m2 3/m3 2 and β2≡m4/m2 2.   3. Determine the family or transformation function used based on the above.       

     The upper and lower limits can then be set based on the estimated parameters from the fitting process. This may involve, for example, identifying the upper and lower bounds for the data points in the fitted distribution such that the estimated parameters indicate an error rate greater than a predetermined threshold. For example, if the error rate is set to 2.5%, then the upper and lower limits for a cohort are set based on the parameters for the fitted Johnson distribution for that cohort that indicate that 95% of all data points in the cohort would likely lie between the upper and lower limits. 
     In the case where there is a single final cohort, the above procedure results in an identification of the final upper and lower limits. In the case where there are multiple final cohorts, as described briefly above, a weighted average of the upper and lower limits from the multiple final cohorts may be determined, with the weights either being preassigned or dynamically determined based on machine learning. The result is final upper and lower limits determined either from a single final cohort or from a weighted average of upper and lower limits from multiple final cohorts. 
     Notably, the procedure above may be repeated for each confidential data type. For example, in the case of compensation information, the procedure above can be used to set upper and lower limits for salary, bonus, and stock compensation independently. 
     The upper and lower limits can then be used to prevent outlier data points from being used for insights provided to other users. This prevention may take many forms, including, for example, removing the submitted confidential data value from the DFS  118 , or simply not providing insights into the confidential data insights data store  122  using that particular submitted confidential data value. Additionally, some confidential data types (e.g., base salary in compensation data) may, if determined to be an outlier, cause related confidential data (e.g., bonus, stock compensation) from the same submission to also be prevented from being used for insights provided to other users. In other words, some types of confidential data are such that, if an outlier is detected, the entire r-tuple is discarded or otherwise not used for insights, while some types of confidential data are such that only those particular confidential data types within the r-tuple are discarded or otherwise not used for insights. 
       FIG. 11  is a flow diagram depicting a method  1100  for handling confidential data submitted by a user in a computer system, in accordance with another example embodiment. The method  1100  may be performed at, for example, the confidential data relevance workflow  120  of  FIG. 1 . 
     At operation  1102 , a submission of confidential data of a first confidential data type is received from a first user via a first computerized user interface. In an example embodiment, this submission may take the form of an r-tuple, as described above. At operation  1104 , one or more attributes of the first user are determined. The one or more attributes of the first user may be determined at a level at which information is available. One common source for attribute information for the first user may be a member profile in a social networking service, where such attributes may be explicitly listed. However, it is not necessary that the attribute information be retrieved from a member profile, or even that the attribute information be explicitly listed (e.g., it can be inferred as well). 
     At operation  1106 , a plurality of previously submitted confidential data values, for a cohort matching the one or more attributes of the first user, of the first confidential data type, are retrieved. At operation  1108 , one or more intermediate cohorts are derived by generalizing each of the one or more attributes of the cohort up at least one level in a different taxonomy corresponding to each of the one or more attributes. As described above, there may be multiple ways this operation may be performed. 
       FIG. 12  is a flow diagram illustrating a method  1200  of deriving one or more intermediate cohorts at operation  1108 , in accordance with a first example embodiment. At operation  1202 , a plurality of intermediate cohorts are derived by generalizing each of the one or more attributes of the cohort up one level. At operation  1204 , it is determined if the number of previously submitted confidential data values in at least one of these intermediate cohorts exceeds a predetermined threshold. If so, then at operation  1206 , at least one of the intermediate cohorts whose number of previously submitted confidential data values exceeded the predetermined threshold is selected. If not, then the method  1200  loops back to operation  1202  for the intermediate cohort having the highest number of previously submitted confidential data values of the intermediate cohorts. 
       FIG. 13  is a flow diagram illustrating a method  1300  of deriving one or more intermediate cohorts at operation  1108 , in accordance with a second example embodiment. At operation  1302 , a plurality of intermediate cohorts are derived by generalizing each of the one or more attributes of the cohort up one level. At operation  1304 , it is determined whether the number of previously submitted confidential data values in the intermediate cohort having the highest number of previously submitted confidential data values exceeds a predetermined threshold. If so, then at operation  1306  the intermediate cohort having the highest number of previously submitted confidential data values is selected. If not, then the method  1300  loops back to operation  1302  for the intermediate cohort having the highest number of previously submitted confidential data values. 
     Referring back to  FIG. 11 , at operation  1110 , a parameterized distribution is fit to the previously submitted confidential data values that are contained within the selected one or more of the intermediate cohorts, outputting one or more estimated parameters for each of the selected one or more of the intermediate cohorts. At operation  1112 , a lower limit for the first confidential data type is set based on the one or more estimated parameters for each of the selected one or more intermediate cohorts. In cases where there are multiple selected intermediate cohorts, this may include calculating a weighted average of lower limits calculated for each of the selected intermediate cohorts. 
     At operation  1114 , an upper limit for the first confidential data type is set based on the one or more estimated parameters for each of the selected one or more intermediate cohorts. In cases where there are multiple selected intermediate cohorts, this may include calculating a weighted average of upper limits calculated for each of the selected intermediate cohorts. 
     At operation  1116 , it is determined whether the confidential data value submitted by the first user is an outlier by determining if the confidential data value submitted by the first user is lower than the lower limit or higher than the upper limit. If so, then at operation  1118  the confidential data value submitted by the first user is prevented from being used for insights provided to other users. 
     Once outliers in the submitted data are removed or otherwise prevented from being included in insight calculations, the system may turn to actually performing the insight calculations used to determine what insights are to be gained from the submitted confidential data. In an example embodiment, for any given cohort, a confidence score may be computed for each confidential data type in the data points of the cohort. Thus, for example, if an insight is desired for compensation data for people with the title of “Software Product Manager” in San Jose, a first confidence score may be computed for base salaries, a second confidence score may be computed for bonuses, a third confidence score may be computed for stock compensation, and so on. 
     In an example embodiment, each of these confidence scores is calculated by multiplying a support score by a non-outlier score. The support score may be defined as: 
     support score=n′/(n′+c), where c is a smoothing constant and n′ is the number of non-outlier entries for that confidential data type. 
     The non-outlier score may be defined as: 
     non-outlier score=n′/n, where n is the total number of non-null entries for that confidential data type. 
     For example, assuming a c value of 20, if there are 15 entries for base salary in a given cohort, with 12 of them being non-outliers, the confidence score would be 12/32*12/15=0.3. 
     The confidence score may be utilized in insight calculations as described in more detail below. 
     The above procedures may be combined to create a unified approach to providing insights based on confidential data submissions.  FIG. 14  is a flow diagram illustrating a method  1400  for handling submission of confidential data in accordance with an example embodiment. 
     At operation  1402 , a slice of user attributes of users who submitted confidential data is identified. This identification may, for example, be received explicitly by a user wishing to view insights on confidential data submitted by other users, or may alternatively be deduced implicitly by the system based, for example, on user attributes of the user who is attempting to view the insights. For example, if the user wishing to view the insights is a computer programmer in the San Francisco Bay Area, the slice selected may be computer programmers in the San Francisco Bay Area. More complex deductions may also be performed. For example, the system may know that people working in the San Francisco Bay Area often will be interested in confidential data submitted by users in other similarly sized cities. As such, the system may deduce that the user may wish to view insights for computer programmers in the San Francisco Bay Area or New York City. Alternatively, the system may deduce that the user wishes to view insights for computer programmers in all of California, or for people in the technology industry in San Francisco. 
     No matter how the slice is determined, once it is identified, then at operation  1404 , one or more submitted confidential data values of a first confidential data type within the slice that have been deemed outliers based on an external data set are excluded from the slice. This may be based, for example, on the method described above with respect to  FIG. 8 . At operation  1406 , one or more submitted confidential data values of the first confidential data type within the slice that have been deemed outliers based on an internal data set are excluded from the slice. This may be based, for example, on the methods described above with respect to  FIGS. 9 and 11 . At operation  1408 , it is determined whether the number of submitted confidential data values, for a confidential data type, remaining in the slice (after the exclusions above) exceeds a predetermined threshold. If not, then at operation  1410 , the information for the confidential data type in the slice is deemed unreliable and not used for insights. This improves functioning of the computer system by preventing costly calculations of confidence scores or insight statistics for confidential data types/slices that will not be reliable anyway. This predetermined threshold may vary based on the slice and slice attributes. For example, for slices including a region attribute, the predetermined threshold may be set lower than for slices not including a region attribute (for example, at the country level, or where no location is specified). 
     If so, however, then at operation  1412 , a confidence score is calculated for the confidential data type within the slice. The confidence score may be calculated, as described above, as being equal to the support score multiplied by the non-outlier score. At operation  1414 , it is determined whether the confidence score exceeds a threshold. If not, then the method  1400  moves to operation  1410 , where the information for the confidential data type in the slice is deemed unreliable and not used for insights. This improves functioning of the computer system by preventing costly calculations of insight statistics for confidential data types/slices that will not be reliable anyway. If so, however, then one or more insight statistics for submitted confidential data values of the confidential data type for the slice (that have not been excluded) can be calculated and used to provide insights to users at operation  1416 . These insight statistics may include, for example, median, average, standard deviation, percentiles, etc. The types of insight statistics calculated may also vary based on the number of non-excluded submitted confidential data values being considered. For example, if the number of non-excluded submitted confidential data values being considered is low, then perhaps average and median will be computed but not percentiles, whereas percentiles would also be calculated if the number of non-excluded submitted confidential data values being considered is high. 
     The method  1400  may be repeated for each confidential data type in the submitted confidential data. It should be noted that certain confidential data types may be considered reflective of the reliability of the overall tuple of confidential data types in which they were submitted. For example, if a tuple includes confidential data types of different types of compensation information (e.g., base salary, bonus, stock, tips, etc.), then the confidential data type of base salary may be reflective of the reliability of the overall tuple. As such, if the confidence score for base salary in a particular slice is low, the system may decide to exclude all confidential data types in the submitted confidential data for that slice, even if some of the other confidential data types, for example bonus, have confidence scores higher than the predetermined threshold. 
       FIGS. 15A-15C  are screen captures illustrating a user interface  1500  for displaying insights to a first user from confidential data submitted by other users, in accordance with an example embodiment. Referring first to  FIG. 15A , the user interface  1500  displays a metric  1502  comparing confidential data of the first user to confidential data of other users in a same slice as the first user. Here, for example, the first user is able to see that his base salary (as selectable via a drop-down menu  1504 ) is higher than that of 70% of other users in the same slice (the slice being depicted as User Experience Designers in the San Francisco Bay Area). This metric is also displayed as a graphic  1506  for easy comparison. 
     Referring now to  FIG. 15B , the user interface  1500  displays salary ranges for users in the same slice as the first user, including a median base salary  1508 , a range of submitted base salaries  1510 , median total compensation  1512 , and a range of submitted total compensations  1514 . 
     Referring now to  FIG. 15C , the user interface  1500  displays insights  1516 ,  1518 ,  1520 , and  1522  for positions related to the position of the first user. Notably, these insights  1516 ,  1518 ,  1520 , and  1522  may require using information from slices other than the one the first user belongs to. In an example embodiment, there is no limitation on the confidential data frontend  104  retrieving insights from the confidential data insights data store  122  that come from slices different from ones to which the user being presented with the insights belongs, although in some example embodiments, the confidential data frontend  104  may itself wish to limit the first user&#39;s ability to ask for and/or view certain types of information (e.g., the confidential data frontend  104  may permit the first user to view salary information for positions related to the first user&#39;s own position, but not unrelated positions). 
     As depicted above, all of the insights may be statistical information derived from confidential data submitted by users other than the user viewing the insights (as well as potentially including the user&#39;s own confidential data as well). 
     Notably, insights can be retrieved in response to a query. This query may be user generated or machine generated. These queries may include values for one or more attributes that define a cohort, as described above. For example, the query may be “show base salaries for computer programmers in Seattle” or “show total compensation for accounting jobs in California.” While the initial query may indicate a particular level of granularity for one or more of the attributes (e.g., California is at the state level of granularity whereas country, region, and city could be different levels of granularity for location), it is common for there not to be enough data to make a relevant insight at the initially specified level of granularity. Generalizing of course improves the reliability of the insight, but makes it less relevant to the user (e.g., if a user wants to know base salaries for computer programmers in Seattle, the system could return an average base salary for all tech workers in the U.S., which would be a fairly reliable statistical insight due to the plethora of data points available, but such a generalized insight would be of little value to the user). 
     In order to address this issue, in an example embodiment statistical insights are automatically generated at a generalized level in a manner that generalizes the least amount possible to provide a desired level of reliability. Specifically, the initial query is mapped into a hierarchy for each specified attribute in the initial query. Then a cohort score is calculated for the combination of attributes in the initial query that indicates the cohort. This cohort score is a weighted combination of a confidence score for the cohort and a granularity score for the cohort. These scores will be described in more detail below. 
     Then all possible generalizations of the cohort within the hierarchies of the attributes specified in the initial query are determined, and the same type of cohort score calculation performed for each of these generalizations. The generalization (including the cohort for the initial query) with the highest cohort score is then selected as the cohort upon which to perform a statistical calculation on submitted confidential data. The results of this statistical calculation can then be returned to the user as the most relevant and reliable insight. 
       FIG. 16  is a diagram illustrating example hierarchies  1600 A,  1600 B,  1600 C,  1600 D for four different attributes types in accordance with an example embodiment. Hierarchy  1600 A generally can be considered a “title” hierarchy, with the lowest level  1602 A indicating an exact title (e.g., software engineer) for a position, the next level  1602 B indicating a supertitle (e.g., computer programming), the next level  1602 C indicating a function (e.g., technology), and the top level  1602 D indicating “all”, specifically that the attribute has no limitation on job title. Notably, in the actual hierarchies, the different levels  1602 A- 1602 C will include multiple potential particular values. This figure is intended only to show the levels of the hierarchies  1600 A- 1600 D. 
     Hierarchy  1600 B generally can be considered a “company” hierarchy, with the lowest level  1604 A indicating an exact company (e.g., Linked-In), the next level  1604 B indicating company peer group (e.g., social networking companies), the next level  1604 C indicating an industry (e.g., technology), and the top level  1604 D indicating “all.” 
     Hierarchy  1600 C generally can be considered a “location” hierarchy, with the lowest level  1606 A indicating a city (e.g., San Jose), the next level  1606 B indicating a region (e.g., San Francisco Bay Area), the next level  1606 C indicating a state (e.g., California), and the top level  1606 D indicating “all.” 
     Hierarchy  1600 D generally can be considered a “range of years of experience” hierarchy, with the lowest level  1608 A indicating a 1 year range, the next level  1608 B indicating a 3 year range, the next level  1608 C indicating a 5 year range, and the top level  1608 D indicating “all.” 
     These are merely example hierarchies and one of ordinary skill in the art will recognize that there may be additional hierarchies and variations on hierarchies depending on implementation. 
     As described above, the cohort generated by the initial query may be determined and then generalized along the hierarchy or hierarchies on which attributes were specified in the initial query. For example, if the initial query specified software engineers in Seattle, then the cohort from the initial query would be at the lowest levels  1602 A,  1606 A in the title hierarchy  1600 A and location hierarchy  1600 C, respectively, because software engineer is at the title level  1602 A and Seattle is at the city level  1606 A. Additional cohorts can then be generated by generalizing each of these attributes up their respective hierarchy, creating cohorts for each combination. Thus, cohorts would be formed based on the combinations of  1602 B and  1606 A,  1602 C and  1606 A,  1602 D and  1606 A,  1602 A and  1606 B,  1602 B and  1606 B,  1602 C and  1606 B,  1602 D and  1606 B,  1602 A and  1606 C,  1602 B and  1606 C,  1602 C and  1606 C,  1602 D and  1606 C,  1602 A and  1606 D,  1602 B and  1606 D,  1602 C and  1606 D, and  1602 D and  1606 D. 
     In another example, if the initial query specified technology (function) workers at Linked-In, then the cohort from the initial query would be at the level of the combination of  1602 C (function level) and  1604 A (company level), and the additional combinations generated as  1602 D and  1604 A,  1602 C and  1604 B,  1602 D and  1604 B,  1602 C and  1604 C,  1602 D and  1604 C,  1602 C and  1604 D, and  1602 D and  1604 D. Notably, the generalizations only occur “up” the respective hierarchies from the initial query, not “down.” 
     All of the cohort combinations, including the cohort formed from the initial query, may then be assigned a cohort score. This cohort score is calculated as a weighed combination of the confidence score for the cohort and a granularity score based on the level of generalization in the respective hierarchies. The confidence score may be generated, for example, using the procedure described earlier with respect to  FIG. 14  and the corresponding text. The granularity score may be calculated in a number of different ways. In an example embodiment, the granularity of a particular cohort is based on a combination of individual granularities. Individual granularity scores may be assigned to each level of each hierarchy, and thus the combination of individual granularities may be calculated as the sum of all individual granularity scores for every level beneath the level being tested. Alternatively, a metric based on usage information may be assigned to each granularity combination. For example, the metric may be “how many times have users queried for this combination, or a combination that this combination would cover.” Thus, if users have queried for insights for software engineers in Seattle 150 times (even if some of these queries included additional attributes, such as company or years of experience), then a granularity score of 150 may be calculated for this combination. 
     Predetermined weights are then assigned to the granularity score and the confidence score in order to calculate the cohort score. In some example embodiments, the weights may be generated based on a machine learning algorithm. 
       FIG. 17  is a block diagram illustrating a cohort score machine learning algorithm component  1700 , in accordance with an example embodiment. In some example embodiments, the cohort score machine learning algorithm component  1700  may be located on the confidential data backend  106 . 
     In a training component  1702 , sample usage information  1704  from a social networking service is fed to a feature extractor  1706 , which acts to extract curated features  1708  from the sample usage information  1704 . 
     Thus, for example, the feature extractor  1706  may extract features such as number of searches, frequency of searches, frequency of selections, etc., from the sample usage information  1704 . Extraction may be performed via a number of different extraction techniques. In an example embodiment, the attributes may be directly extracted from the sample usage information  1704 . In other example embodiments, more complex transformations and/or pre-processing may be performed, such as mapping of the member profile attributes to social network attribute taxonomy categories. 
     The curated features  1708  may be fed to a machine learning algorithm  1710  along with labels  1712  for each of the pieces of sample usage information  1704 . The machine learning algorithm  1710  then trains a cohort score model  1714  based on the curated features  1708  and labels  1712 . The machine learning algorithm  1710  may be selected from among many different potential supervised or unsupervised machine learning algorithms. Examples of supervised machine learning algorithms include artificial neural networks, Bayesian networks, instance-based learning, support vector machines, random forests, linear classifiers, quadratic classifiers, k-nearest neighbor, decision trees, and hidden Markov models. Examples of unsupervised machine learning algorithms include expectation-maximization algorithms, vector quantization, and information bottleneck method. In an example embodiment, a binary logistic regression model is used. Binary logistic regression deals with situations in which the observed outcome for a dependent variable can have only two possible types. Logistic regression is used to predict the odds of one case or the other being true based on values of independent variables (predictors). 
     Specifically, the cohort score model  1714  may be trained to output weights for the confidence score and cohort score. 
     In a prediction component  1716 , a candidate cohort is used to generate candidate usage information  1718 , which is fed to a feature extractor  1720 , which acts to extract curated features  1722  from the candidate usage information  1718 . The curated features  1722  are then used as input to the trained cohort score model  1714 , which outputs the weights to use to calculate the cohort score for the candidate cohort. 
     It should be noted that while the feature extractor  1706  and the feature extractor  1720  are depicted as separate components, they may be the same component in some example embodiments. Additionally, a large number of different types of features could be extracted using the feature extractors  1706  and  1720 . Furthermore, while in an example embodiment the features extracted by the feature extractor  1706  are the same as the features extracted by the feature extractor  1720 , in other example embodiments there may be differences in the features. 
       FIG. 18  is a flow diagram illustrating a method  1800  of providing a response to a query on previously submitted confidential data values, in accordance with an example embodiment. At operation  1802 , a query on a plurality of previously submitted confidential data values for a first cohort having one or more attributes is obtained. Then a loop is begun for each of the one or more attributes. At operation  1804 , a level in a hierarchy corresponding to an attribute type for the attribute is determined. At operation  1806 , it is determined if there are any more attributes in the first cohort. If so, then the method  1800  loops to operation  1804  for the next attribute. If not, then at operation  1808  one or more additional cohorts are formed, corresponding to different combinations of generalizations of the one or more attributes up one or more levels in each hierarchy corresponding to an attribute type for each attribute. Then a loop is begun for each cohort (the first and the additional). At operation  1810 , a confidence score for a statistical function performed on the previously submitted confidential data values in the cohort is calculated. At operation  1812 , a granularity score is calculated based on the levels of attributes in each hierarchy for the cohort. At operation  1814 , a cohort score is calculated based on a weighted combination of the confidence score and the granularity score. 
     At operation  1816 , it is determined if there are any more cohorts. If so, then the method  1800  loops back to operation  1810  for the next cohort. If not, then at operation  1818  the statistical function is performed on the previously submitted confidential data values for a cohort having the highest cohort score. Then at operation  1820 , a response to the query, including a result from the statistical function, is formulated. 
     Modules, Components, and Logic 
     Certain embodiments are described herein as including logic or a number of components, modules, or mechanisms. Modules may constitute either software modules (e.g., code embodied on a machine-readable medium) or hardware modules. A “hardware module” is a tangible unit capable of performing certain operations and may be configured or arranged in a certain physical manner. In various example embodiments, one or more computer systems (e.g., a standalone computer system, a client computer system, or a server computer system) or one or more hardware modules of a computer system (e.g., a processor or a group of processors) may be configured by software (e.g., an application or application portion) as a hardware module that operates to perform certain operations as described herein. 
     In some embodiments, a hardware module may be implemented mechanically, electronically, or any suitable combination thereof. For example, a hardware module may include dedicated circuitry or logic that is permanently configured to perform certain operations. For example, a hardware module may be a special-purpose processor, such as a Field-Programmable Gate Array (FPGA) or an Application Specific Integrated Circuit (ASIC). A hardware module may also include programmable logic or circuitry that is temporarily configured by software to perform certain operations. For example, a hardware module may include software executed by a general-purpose processor or other programmable processor. Once configured by such software, hardware modules become specific machines (or specific components of a machine) uniquely tailored to perform the configured functions and are no longer general-purpose processors. It will be appreciated that the decision to implement a hardware module mechanically, in dedicated and permanently configured circuitry, or in temporarily configured circuitry (e.g., configured by software) may be driven by cost and time considerations. 
     Accordingly, the phrase “hardware module” should be understood to encompass a tangible entity, be that an entity that is physically constructed, permanently configured (e.g., hardwired), or temporarily configured (e.g., programmed) to operate in a certain manner or to perform certain operations described herein. As used herein, “hardware-implemented module” refers to a hardware module. Considering embodiments in which hardware modules are temporarily configured (e.g., programmed), each of the hardware modules need not be configured or instantiated at any one instance in time. For example, where a hardware module comprises a general-purpose processor configured by software to become a special-purpose processor, the general-purpose processor may be configured as respectively different special-purpose processors (e.g., comprising different hardware modules) at different times. Software accordingly configures a particular processor or processors, for example, to constitute a particular hardware module at one instance of time and to constitute a different hardware module at a different instance of time. 
     Hardware modules can provide information to, and receive information from, other hardware modules. Accordingly, the described hardware modules may be regarded as being communicatively coupled. Where multiple hardware modules exist contemporaneously, communications may be achieved through signal transmission (e.g., over appropriate circuits and buses) between or among two or more of the hardware modules. In embodiments in which multiple hardware modules are configured or instantiated at different times, communications between such hardware modules may be achieved, for example, through the storage and retrieval of information in memory structures to which the multiple hardware modules have access. For example, one hardware module may perform an operation and store the output of that operation in a memory device to which it is communicatively coupled. A further hardware module may then, at a later time, access the memory device to retrieve and process the stored output. Hardware modules may also initiate communications with input or output devices, and can operate on a resource (e.g., a collection of information). 
     The various operations of example methods described herein may be performed, at least partially, by one or more processors that are temporarily configured (e.g., by software) or permanently configured to perform the relevant operations. Whether temporarily or permanently configured, such processors may constitute processor-implemented modules that operate to perform one or more operations or functions described herein. As used herein, “processor-implemented module” refers to a hardware module implemented using one or more processors. 
     Similarly, the methods described herein may be at least partially processor-implemented, with a particular processor or processors being an example of hardware. For example, at least some of the operations of a method may be performed by one or more processors or processor-implemented modules. Moreover, the one or more processors may also operate to support performance of the relevant operations in a “cloud computing” environment or as a “software as a service” (SaaS). For example, at least some of the operations may be performed by a group of computers (as examples of machines including processors), with these operations being accessible via a network (e.g., the Internet) and via one or more appropriate interfaces (e.g., an API). 
     The performance of certain of the operations may be distributed among the processors, not only residing within a single machine, but deployed across a number of machines. In some example embodiments, the processors or processor-implemented modules may be located in a single geographic location (e.g., within a home environment, an office environment, or a server farm). In other example embodiments, the processors or processor-implemented modules may be distributed across a number of geographic locations. 
     Machine and Software Architecture 
     The modules, methods, applications, and so forth described in conjunction with  FIGS. 1-18  are implemented in some embodiments in the context of a machine and an associated software architecture. The sections below describe representative software architecture(s) and machine (e.g., hardware) architecture(s) that are suitable for use with the disclosed embodiments. 
     Software architectures are used in conjunction with hardware architectures to create devices and machines tailored to particular purposes. For example, a particular hardware architecture coupled with a particular software architecture will create a mobile device, such as a mobile phone, tablet device, or so forth. A slightly different hardware and software architecture may yield a smart device for use in the “internet of things,” while yet another combination produces a server computer for use within a cloud computing architecture. Not all combinations of such software and hardware architectures are presented here, as those of skill in the art can readily understand how to implement the inventive subject matter in different contexts from the disclosure contained herein. 
     Software Architecture 
       FIG. 19  is a block diagram  1900  illustrating a representative software architecture  1902 , which may be used in conjunction with various hardware architectures herein described.  FIG. 19  is merely a non-limiting example of a software architecture, and it will be appreciated that many other architectures may be implemented to facilitate the functionality described herein. The software architecture  1902  may be executing on hardware such as a machine  2000  of  FIG. 20  that includes, among other things, processors  2010 , memory/storage  2030 , and I/O components  2050 . A representative hardware layer  1904  is illustrated and can represent, for example, the machine  2000  of  FIG. 20 . The representative hardware layer  1904  comprises one or more processing units  1906  having associated executable instructions  1908 . The executable instructions  1908  represent the executable instructions of the software architecture  1902 , including implementation of the methods, modules, and so forth of  FIGS. 1-18 . The hardware layer  1904  also includes memory and/or storage modules  1910 , which also have the executable instructions  1908 . The hardware layer  1904  may also comprise other hardware  1912 , which represents any other hardware of the hardware layer  1904 , such as the other hardware illustrated as part of the machine  2000 . 
     In the example architecture of  FIG. 19 , the software architecture  1902  may be conceptualized as a stack of layers where each layer provides particular functionality. For example, the software architecture  1902  may include layers such as an operating system  1914 , libraries  1916 , frameworks/middleware  1918 , applications  1920 , and a presentation layer  1944 . Operationally, the applications  1920  and/or other components within the layers may invoke API calls  1924  through the software stack and receive responses, returned values, and so forth, illustrated as messages  1926 , in response to the API calls  1924 . The layers illustrated are representative in nature and not all software architectures have all layers. For example, some mobile or special-purpose operating systems may not provide a layer of frameworks/middleware  1918 , while others may provide such a layer. Other software architectures may include additional or different layers. 
     The operating system  1914  may manage hardware resources and provide common services. The operating system  1914  may include, for example, a kernel  1928 , services  1930 , and drivers  1932 . The kernel  1928  may act as an abstraction layer between the hardware and the other software layers. For example, the kernel  1928  may be responsible for memory management, processor management (e.g., scheduling), component management, networking, security settings, and so on. The services  1930  may provide other common services for the other software layers. The drivers  1932  may be responsible for controlling or interfacing with the underlying hardware. For instance, the drivers  1932  may include display drivers, camera drivers, Bluetooth® drivers, flash memory drivers, serial communication drivers (e.g., Universal Serial Bus (USB) drivers), Wi-Fi® drivers, audio drivers, power management drivers, and so forth depending on the hardware configuration. 
     The libraries  1916  may provide a common infrastructure that may be utilized by the applications  1920  and/or other components and/or layers. The libraries  1916  typically provide functionality that allows other software modules to perform tasks in an easier fashion than by interfacing directly with the underlying operating system  1914  functionality (e.g., kernel  1928 , services  1930 , and/or drivers  1932 ). The libraries  1916  may include system libraries  1934  (e.g., C standard library) that may provide functions such as memory allocation functions, string manipulation functions, mathematical functions, and the like. In addition, the libraries  1916  may include API libraries  1936  such as media libraries (e.g., libraries to support presentation and manipulation of various media formats such as MPEG4, H.264, MP3, AAC, AMR, JPG, PNG), graphics libraries (e.g., an OpenGL framework that may be used to render 2D and 3D graphic content on a display), database libraries (e.g., SQLite that may provide various relational database functions), web libraries (e.g., WebKit that may provide web browsing functionality), and the like. The libraries  1916  may also include a wide variety of other libraries  1938  to provide many other APIs to the applications  1920  and other software components/modules. 
     The frameworks  1918  (also sometimes referred to as middleware) may provide a higher-level common infrastructure that may be utilized by the applications  1920  and/or other software components/modules. For example, the frameworks  1918  may provide various graphic user interface (GUI) functions, high-level resource management, high-level location services, and so forth. The frameworks  1918  may provide a broad spectrum of other APIs that may be utilized by the applications  1920  and/or other software components/modules, some of which may be specific to a particular operating system or platform. 
     The applications  1920  include built-in applications  1940  and/or third-party applications  1942 . Examples of representative built-in applications  1940  may include, but are not limited to, a contacts application, a browser application, a book reader application, a location application, a media application, a messaging application, and/or a game application. The third-party applications  1942  may include any of the built-in applications  1940  as well as a broad assortment of other applications. In a specific example, the third-party application  1942  (e.g., an application developed using the Android™ or iOS™ software development kit (SDK) by an entity other than the vendor of the particular platform) may be mobile software running on a mobile operating system such as iOS™, Android™, Windows® Phone, or other mobile operating systems. In this example, the third-party application  1942  may invoke the API calls  1924  provided by the mobile operating system such as the operating system  1914  to facilitate functionality described herein. 
     The applications  1920  may utilize built-in operating system  1914  functions (e.g., kernel  1928 , services  1930 , and/or drivers  1932 ), libraries  1916  (e.g., system libraries  1934 , API libraries  1936 , and other libraries  1938 ), and frameworks/middleware  1918  to create user interfaces to interact with users of the system. Alternatively, or additionally, in some systems, interactions with a user may occur through a presentation layer, such as the presentation layer  1944 . In these systems, the application/module “logic” can be separated from the aspects of the application/module that interact with a user. 
     Some software architectures utilize virtual machines. In the example of  FIG. 19 , this is illustrated by a virtual machine  1948 . A virtual machine creates a software environment where applications/modules can execute as if they were executing on a hardware machine (such as the machine  2000  of  FIG. 20 , for example). A virtual machine is hosted by a host operating system (e.g., operating system  1914  in  FIG. 19 ) and typically, although not always, has a virtual machine monitor  1946 , which manages the operation of the virtual machine  1948  as well as the interface with the host operating system (e.g., operating system  1914 ). A software architecture executes within the virtual machine  1948 , such as an operating system  1950 , libraries  1952 , frameworks/middleware  1954 , applications  1956 , and/or a presentation layer  1958 . These layers of software architecture executing within the virtual machine  1948  can be the same as corresponding layers previously described or may be different. 
     Example Machine Architecture and Machine-Readable Medium 
       FIG. 20  is a block diagram illustrating components of a machine  2000 , according to some example embodiments, able to read instructions from a machine-readable medium (e.g., a machine-readable storage medium) and perform any one or more of the methodologies discussed herein. Specifically,  FIG. 20  shows a diagrammatic representation of the machine  2000  in the example form of a computer system, within which instructions  2016  (e.g., software, a program, an application, an applet, an app, or other executable code) for causing the machine  2000  to perform any one or more of the methodologies discussed herein may be executed. The instructions  2016  transform the general, non-programmed machine into a particular machine programmed to carry out the described and illustrated functions in the manner described. In alternative embodiments, the machine  2000  operates as a standalone device or may be coupled (e.g., networked) to other machines. In a networked deployment, the machine  2000  may operate in the capacity of a server machine or a client machine in a server-client network environment, or as a peer machine in a peer-to-peer (or distributed) network environment. The machine  2000  may comprise, but not be limited to, a server computer, a client computer, a personal computer (PC), a tablet computer, a laptop computer, a netbook, a set-top box (STB), a personal digital assistant (PDA), an entertainment media system, a cellular telephone, a smart phone, a mobile device, a wearable device (e.g., a smart watch), a smart home device (e.g., a smart appliance), other smart devices, a web appliance, a network router, a network switch, a network bridge, or any machine capable of executing the instructions  2016 , sequentially or otherwise, that specify actions to be taken by the machine  2000 . Further, while only a single machine  2000  is illustrated, the term “machine” shall also be taken to include a collection of machines  2000  that individually or jointly execute the instructions  2016  to perform any one or more of the methodologies discussed herein. 
     The machine  2000  may include processors  2010 , memory/storage  2030 , and I/O components  2050 , which may be configured to communicate with each other such as via a bus  2002 . In an example embodiment, the processors  2010  (e.g., a Central Processing Unit (CPU), a Reduced Instruction Set Computing (RISC) processor, a Complex Instruction Set Computing (CISC) processor, a Graphics Processing Unit (GPU), a Digital Signal Processor (DSP), an ASIC, a Radio-Frequency Integrated Circuit (RFIC), another processor, or any suitable combination thereof) may include, for example, a processor  2012  and a processor  2014  that may execute the instructions  2016 . The term “processor” is intended to include multi-core processors that may comprise two or more independent processors (sometimes referred to as “cores”) that may execute the instructions  2016  contemporaneously. Although  FIG. 20  shows multiple processors  2010 , the machine  2000  may include a single processor with a single core, a single processor with multiple cores (e.g., a multi-core processor), multiple processors with a single core, multiple processors with multiples cores, or any combination thereof. 
     The memory/storage  2030  may include a memory  2032 , such as a main memory, or other memory storage, and a storage unit  2036 , both accessible to the processors  2010  such as via the bus  2002 . The storage unit  2036  and memory  2032  store the instructions  2016  embodying any one or more of the methodologies or functions described herein. The instructions  2016  may also reside, completely or partially, within the memory  2032 , within the storage unit  2036 , within at least one of the processors  2010  (e.g., within the processor&#39;s cache memory), or any suitable combination thereof, during execution thereof by the machine  2000 . Accordingly, the memory  2032 , the storage unit  2036 , and the memory of the processors  2010  are examples of machine-readable media. 
     As used herein, “machine-readable medium” means a device able to store instructions and data temporarily or permanently and may include, but is not limited to, random-access memory (RAM), read-only memory (ROM), buffer memory, flash memory, optical media, magnetic media, cache memory, other types of storage (e.g., Erasable Programmable Read-Only Memory (EEPROM)), and/or any suitable combination thereof. The term “machine-readable medium” should be taken to include a single medium or multiple media (e.g., a centralized or distributed database, or associated caches and servers) able to store the instructions  2016 . The term “machine-readable medium” shall also be taken to include any medium, or combination of multiple media, that is capable of storing instructions (e.g., instructions  2016 ) for execution by a machine (e.g., machine  2000 ), such that the instructions, when executed by one or more processors of the machine (e.g., processors  2010 ), cause the machine to perform any one or more of the methodologies described herein. Accordingly, a “machine-readable medium” refers to a single storage apparatus or device, as well as “cloud-based” storage systems or storage networks that include multiple storage apparatus or devices. The term “machine-readable medium” excludes signals per se. 
     The I/O components  2050  may include a wide variety of components to receive input, provide output, produce output, transmit information, exchange information, capture measurements, and so on. The specific I/O components  2050  that are included in a particular machine will depend on the type of machine. For example, portable machines such as mobile phones will likely include a touch input device or other such input mechanisms, while a headless server machine will likely not include such a touch input device. It will be appreciated that the I/O components  2050  may include many other components that are not shown in  FIG. 20 . The I/O components  2050  are grouped according to functionality merely for simplifying the following discussion and the grouping is in no way limiting. In various example embodiments, the I/O components  2050  may include output components  2052  and input components  2054 . The output components  2052  may include visual components (e.g., a display such as a plasma display panel (PDP), a light emitting diode (LED) display, a liquid crystal display (LCD), a projector, or a cathode ray tube (CRT)), acoustic components (e.g., speakers), haptic components (e.g., a vibratory motor, resistance mechanisms), other signal generators, and so forth. The input components  2054  may include alphanumeric input components (e.g., a keyboard, a touch screen configured to receive alphanumeric input, a photo-optical keyboard, or other alphanumeric input components), point based input components (e.g., a mouse, a touchpad, a trackball, a joystick, a motion sensor, or another pointing instrument), tactile input components (e.g., a physical button, a touch screen that provides location and/or force of touches or touch gestures, or other tactile input components), audio input components (e.g., a microphone), and the like. 
     In further example embodiments, the I/O components  2050  may include biometric components  2056 , motion components  2058 , environmental components  2060 , or position components  2062 , among a wide array of other components. For example, the biometric components  2056  may include components to detect expressions (e.g., hand expressions, facial expressions, vocal expressions, body gestures, or eye tracking), measure biosignals (e.g., blood pressure, heart rate, body temperature, perspiration, or brain waves), identify a person (e.g., voice identification, retinal identification, facial identification, fingerprint identification, or electroencephalogram based identification), and the like. The motion components  2058  may include acceleration sensor components (e.g., accelerometer), gravitation sensor components, rotation sensor components (e.g., gyroscope), and so forth. The environmental components  2060  may include, for example, illumination sensor components (e.g., photometer), temperature sensor components (e.g., one or more thermometers that detect ambient temperature), humidity sensor components, pressure sensor components (e.g., barometer), acoustic sensor components (e.g., one or more microphones that detect background noise), proximity sensor components (e.g., infrared sensors that detect nearby objects), gas sensors (e.g., gas detection sensors to detect concentrations of hazardous gases for safety or to measure pollutants in the atmosphere), or other components that may provide indications, measurements, or signals corresponding to a surrounding physical environment. The position components  2062  may include location sensor components (e.g., a Global Position System (GPS) receiver component), altitude sensor components (e.g., altimeters or barometers that detect air pressure from which altitude may be derived), orientation sensor components (e.g., magnetometers), and the like. 
     Communication may be implemented using a wide variety of technologies. The I/O components  2050  may include communication components  2064  operable to couple the machine  2000  to a network  2080  or devices  2070  via a coupling  2082  and a coupling  2072 , respectively. For example, the communication components  2064  may include a network interface component or other suitable device to interface with the network  2080 . In further examples, the communication components  2064  may include wired communication components, wireless communication components, cellular communication components, Near Field Communication (NFC) components, Bluetooth® components (e.g., Bluetooth® Low Energy), Wi-Fi® components, and other communication components to provide communication via other modalities. The devices  2070  may be another machine or any of a wide variety of peripheral devices (e.g., a peripheral device coupled via a USB). 
     Moreover, the communication components  2064  may detect identifiers or include components operable to detect identifiers. For example, the communication components  2064  may include Radio Frequency Identification (RFID) tag reader components, NFC smart tag detection components, optical reader components (e.g., an optical sensor to detect one-dimensional bar codes such as Universal Product Code (UPC) bar code, multi-dimensional bar codes such as Quick Response (QR) code, Aztec code, Data Matrix, Dataglyph, MaxiCode, PDF417, Ultra Code, UCC RSS-2D bar code, and other optical codes), or acoustic detection components (e.g., microphones to identify tagged audio signals). In addition, a variety of information may be derived via the communication components  2064 , such as location via Internet Protocol (IP) geolocation, location via Wi-Fi® signal triangulation, location via detecting an NFC beacon signal that may indicate a particular location, and so forth. 
     Transmission Medium 
     In various example embodiments, one or more portions of the network  2080  may be an ad hoc network, an intranet, an extranet, a virtual private network (VPN), a local area network (LAN), a wireless LAN (WLAN), a wide area network (WAN), a wireless WAN (WWAN), a metropolitan area network (MAN), the Internet, a portion of the Internet, a portion of the Public Switched Telephone Network (PSTN), a plain old telephone service (POTS) network, a cellular telephone network, a wireless network, a Wi-Fi® network, another type of network, or a combination of two or more such networks. For example, the network  2080  or a portion of the network  2080  may include a wireless or cellular network and the coupling  2082  may be a Code Division Multiple Access (CDMA) connection, a Global System for Mobile communications (GSM) connection, or another type of cellular or wireless coupling. In this example, the coupling  2082  may implement any of a variety of types of data transfer technology, such as Single Carrier Radio Transmission Technology (1×RTT), Evolution-Data Optimized (EVDO) technology, General Packet Radio Service (GPRS) technology, Enhanced Data rates for GSM Evolution (EDGE) technology, third Generation Partnership Project (3GPP) including 3G, fourth generation wireless (4G) networks, Universal Mobile Telecommunications System (UMTS), High Speed Packet Access (HSPA), Worldwide Interoperability for Microwave Access (WiMAX), Long Term Evolution (LTE) standard, others defined by various standard-setting organizations, other long range protocols, or other data transfer technology. 
     The instructions  2016  may be transmitted or received over the network  2080  using a transmission medium via a network interface device (e.g., a network interface component included in the communication components  2064 ) and utilizing any one of a number of well-known transfer protocols (e.g., Hypertext Transfer Protocol (HTTP)). Similarly, the instructions  2016  may be transmitted or received using a transmission medium via the coupling  2072  (e.g., a peer-to-peer coupling) to the devices  2070 . The term “transmission medium” shall be taken to include any intangible medium that is capable of storing, encoding, or carrying the instructions  2016  for execution by the machine  2000 , and includes digital or analog communications signals or other intangible media to facilitate communication of such software. 
     Language 
     Throughout this specification, plural instances may implement components, operations, or structures described as a single instance. Although individual operations of one or more methods are illustrated and described as separate operations, one or more of the individual operations may be performed concurrently, and nothing requires that the operations be performed in the order illustrated. Structures and functionality presented as separate components in example configurations may be implemented as a combined structure or component. Similarly, structures and functionality presented as a single component may be implemented as separate components. These and other variations, modifications, additions, and improvements fall within the scope of the subject matter herein. 
     Although an overview of the inventive subject matter has been described with reference to specific example embodiments, various modifications and changes may be made to these embodiments without departing from the broader scope of embodiments of the present disclosure. Such embodiments of the inventive subject matter may be referred to herein, individually or collectively, by the term “invention” merely for convenience and without intending to voluntarily limit the scope of this application to any single disclosure or inventive concept if more than one is, in fact, disclosed. 
     The embodiments illustrated herein are described in sufficient detail to enable those skilled in the art to practice the teachings disclosed. Other embodiments may be used and derived therefrom, such that structural and logical substitutions and changes may be made without departing from the scope of this disclosure. The Detailed Description, therefore, is not to be taken in a limiting sense, and the scope of various embodiments is defined only by the appended claims, along with the full range of equivalents to which such claims are entitled. 
     As used herein, the term “or” may be construed in either an inclusive or exclusive sense. Moreover, plural instances may be provided for resources, operations, or structures described herein as a single instance. Additionally, boundaries between various resources, operations, modules, engines, and data stores are somewhat arbitrary, and particular operations are illustrated in a context of specific illustrative configurations. Other allocations of functionality are envisioned and may fall within a scope of various embodiments of the present disclosure. In general, structures and functionality presented as separate resources in the example configurations may be implemented as a combined structure or resource. Similarly, structures and functionality presented as a single resource may be implemented as separate resources. These and other variations, modifications, additions, and improvements fall within a scope of embodiments of the present disclosure as represented by the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.