<?xml version="1.0" encoding="utf-8"?>
<!--XBRL document created with Toppan Merrill Bridge  11.4.0.1 -->
<!--Based on XBRL 2.1-->
<!--Created on: 8/6/2026 4:00:37 PM-->
<!--Modified on: 8/6/2026 4:00:37 PM-->
<xsd:schema xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xl="http://www.xbrl.org/2003/XLink" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:ref="http://www.xbrl.org/2006/ref" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:utr="http://www.xbrl.org/2009/utr" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" targetNamespace="http://www.informationsg.com/20260630" attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:us-gaap="http://fasb.org/us-gaap/2026" xmlns:negated="http://www.xbrl.org/2009/role/negated" xmlns:dtr-types="http://www.xbrl.org/dtr/type/2024-01-31" xmlns:iii="http://www.informationsg.com/20260630" xmlns:enum2="http://xbrl.org/2020/extensible-enumerations-2.0" xmlns:us-roles="http://fasb.org/us-roles/2026" xmlns:stpr="http://xbrl.sec.gov/stpr/2026" xmlns:attributeFormDefault="unqualified" xmlns:srt="http://fasb.org/srt/2026" xmlns:deprecated="http://www.xbrl.org/2009/role/deprecated" xmlns:net="http://www.xbrl.org/2009/role/net" xmlns:dei="http://xbrl.sec.gov/dei/2026" xmlns:dtr="http://www.xbrl.org/2009/dtr" xmlns:xbrldi="http://xbrl.org/2006/xbrldi" xmlns:ecd="http://xbrl.sec.gov/ecd/2026" xmlns:ecd-sub="http://xbrl.sec.gov/ecd-sub/2026">
  <xsd:annotation>
    <xsd:appinfo>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureStandardAndCustomAxisDomainDefaults" id="DisclosureStandardAndCustomAxisDomainDefaults">
        <link:definition>99900 - Disclosure - Standard And Custom Axis Domain Defaults</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/StatementCondensedConsolidatedBalanceSheets" id="StatementCondensedConsolidatedBalanceSheets">
        <link:definition>995200100 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/StatementCondensedConsolidatedStatementsOfIncomeAndComprehensiveIncome" id="StatementCondensedConsolidatedStatementsOfIncomeAndComprehensiveIncome">
        <link:definition>995200200 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF INCOME AND COMPREHENSIVE INCOME</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/StatementCondensedConsolidatedStatementsOfCashFlows" id="StatementCondensedConsolidatedStatementsOfCashFlows">
        <link:definition>995200400 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureSummaryOfSignificantAccountingPoliciesFairValueOnRecurringBasisDetails" id="DisclosureSummaryOfSignificantAccountingPoliciesFairValueOnRecurringBasisDetails">
        <link:definition>99940301 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Fair Value on a Recurring Basis (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureAcquisitionMartinoPartnersAcquisitionPreliminaryAllocationOfPurchasePriceToEstimatedFairValuesOfAssetsAcquiredAndLiabilitiesAssumedDetails" id="DisclosureAcquisitionMartinoPartnersAcquisitionPreliminaryAllocationOfPurchasePriceToEstimatedFairValuesOfAssetsAcquiredAndLiabilitiesAssumedDetails">
        <link:definition>99940403 - Disclosure - ACQUISITION - Martino &amp; Partners Acquisition - Preliminary Allocation of the Purchase Price to the Estimated Fair Values of the Assets Acquired and Liabilities Assumed (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureNetIncomePerCommonShareComputationDetails" id="DisclosureNetIncomePerCommonShareComputationDetails">
        <link:definition>99940602 - Disclosure - NET INCOME PER COMMON SHARE - Computation (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureSegmentAndGeographicalInformationReconciliationDetails" id="DisclosureSegmentAndGeographicalInformationReconciliationDetails">
        <link:definition>99940902 - Disclosure - SEGMENT AND GEOGRAPHICAL INFORMATION - Reconciliation (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DocumentDocumentAndEntityInformation" id="DocumentDocumentAndEntityInformation">
        <link:definition>995200090 - Document - Document And Entity Information</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/StatementCondensedConsolidatedBalanceSheetsParenthetical" id="StatementCondensedConsolidatedBalanceSheetsParenthetical">
        <link:definition>995200105 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/StatementCondensedConsolidatedStatementsOfIncomeAndComprehensiveIncomeParenthetical" id="StatementCondensedConsolidatedStatementsOfIncomeAndComprehensiveIncomeParenthetical">
        <link:definition>995200205 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF INCOME AND COMPREHENSIVE INCOME (Parenthetical)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/StatementCondensedConsolidatedStatementsOfStockholdersEquity" id="StatementCondensedConsolidatedStatementsOfStockholdersEquity">
        <link:definition>995200300 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/StatementCondensedConsolidatedStatementsOfStockholdersEquityParenthetical" id="StatementCondensedConsolidatedStatementsOfStockholdersEquityParenthetical">
        <link:definition>995200305 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureDescriptionOfOrganizationAndBusinessOperations" id="DisclosureDescriptionOfOrganizationAndBusinessOperations">
        <link:definition>995210101 - Disclosure - DESCRIPTION OF ORGANIZATION AND BUSINESS OPERATIONS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureBasisOfPresentation" id="DisclosureBasisOfPresentation">
        <link:definition>995210201 - Disclosure - BASIS OF PRESENTATION</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureSummaryOfSignificantAccountingPolicies" id="DisclosureSummaryOfSignificantAccountingPolicies">
        <link:definition>995210301 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureAcquisition" id="DisclosureAcquisition">
        <link:definition>995210401 - Disclosure - ACQUISITION</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureNetIncomePerCommonShare" id="DisclosureNetIncomePerCommonShare">
        <link:definition>995210601 - Disclosure - NET INCOME PER COMMON SHARE</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureIncomeTaxes" id="DisclosureIncomeTaxes">
        <link:definition>995210701 - Disclosure - INCOME TAXES</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureCommitmentsAndContingencies" id="DisclosureCommitmentsAndContingencies">
        <link:definition>995210801 - Disclosure - COMMITMENTS AND CONTINGENCIES</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureSegmentAndGeographicalInformation" id="DisclosureSegmentAndGeographicalInformation">
        <link:definition>995210901 - Disclosure - SEGMENT AND GEOGRAPHICAL INFORMATION</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureFinancingArrangementsAndLongTermDebt" id="DisclosureFinancingArrangementsAndLongTermDebt">
        <link:definition>995211001 - Disclosure - FINANCING ARRANGEMENTS AND LONG-TERM DEBT</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureSubsequentEvents" id="DisclosureSubsequentEvents">
        <link:definition>995211101 - Disclosure - SUBSEQUENT EVENTS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureSummaryOfSignificantAccountingPoliciesPolicies" id="DisclosureSummaryOfSignificantAccountingPoliciesPolicies">
        <link:definition>99920302 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureSummaryOfSignificantAccountingPoliciesTables" id="DisclosureSummaryOfSignificantAccountingPoliciesTables">
        <link:definition>99930303 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureNetIncomePerCommonShareTables" id="DisclosureNetIncomePerCommonShareTables">
        <link:definition>99930603 - Disclosure - NET INCOME PER COMMON SHARE (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureSegmentAndGeographicalInformationTables" id="DisclosureSegmentAndGeographicalInformationTables">
        <link:definition>99930903 - Disclosure - SEGMENT AND GEOGRAPHICAL INFORMATION (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureDescriptionOfOrganizationAndBusinessOperationsDetails" id="DisclosureDescriptionOfOrganizationAndBusinessOperationsDetails">
        <link:definition>99940101 - Disclosure - DESCRIPTION OF ORGANIZATION AND BUSINESS OPERATIONS (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureBasisOfPresentationDetails" id="DisclosureBasisOfPresentationDetails">
        <link:definition>99940201 - Disclosure - BASIS OF PRESENTATION (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureAcquisitionAiMaturityIndexAcquisitionDetails" id="DisclosureAcquisitionAiMaturityIndexAcquisitionDetails">
        <link:definition>99940401 - Disclosure - ACQUISITION - AI Maturity Index Acquisition (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureAcquisitionMartinoPartnersAcquisitionDetails" id="DisclosureAcquisitionMartinoPartnersAcquisitionDetails">
        <link:definition>99940402 - Disclosure - ACQUISITION - Martino &amp; Partners Acquisition (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureAcquisitionMartinoPartnersAcquisitionPurchasePriceAllocationToIntangibleAssetsDetails" id="DisclosureAcquisitionMartinoPartnersAcquisitionPurchasePriceAllocationToIntangibleAssetsDetails">
        <link:definition>99940404 - Disclosure - ACQUISITION - Martino &amp; Partners Acquisition - Purchase price allocation to intangible assets (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureRevenueNarrativeDetails" id="DisclosureRevenueNarrativeDetails">
        <link:definition>99940502 - Disclosure - REVENUE - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureRevenueNarrativeDefaultDetails" id="DisclosureRevenueNarrativeDefaultDetails">
        <link:definition>40502 - Disclosure - REVENUE - Narrative Default (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureRevenueAccountsReceivableAndContractAssetsDetails" id="DisclosureRevenueAccountsReceivableAndContractAssetsDetails">
        <link:definition>99940503 - Disclosure - REVENUE - Accounts Receivable and Contract Assets (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureRevenueAccountsReceivableAndContractAssetsDefaultDetails" id="DisclosureRevenueAccountsReceivableAndContractAssetsDefaultDetails">
        <link:definition>40503 - Disclosure - REVENUE - Accounts Receivable and Contract Assets Default (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureNetIncomePerCommonShareAntidilutiveSecuritiesDetails" id="DisclosureNetIncomePerCommonShareAntidilutiveSecuritiesDetails">
        <link:definition>99940601 - Disclosure - NET INCOME PER COMMON SHARE - Antidilutive Securities (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureIncomeTaxesDetails" id="DisclosureIncomeTaxesDetails">
        <link:definition>99940701 - Disclosure - INCOME TAXES (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureCommitmentsAndContingenciesDetails" id="DisclosureCommitmentsAndContingenciesDetails">
        <link:definition>99940801 - Disclosure - COMMITMENTS AND CONTINGENCIES (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureCommitmentsAndContingenciesDefaultDetails" id="DisclosureCommitmentsAndContingenciesDefaultDetails">
        <link:definition>40801 - Disclosure - COMMITMENTS AND CONTINGENCIES Default (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureSegmentAndGeographicalInformationDetails" id="DisclosureSegmentAndGeographicalInformationDetails">
        <link:definition>99940901 - Disclosure - SEGMENT AND GEOGRAPHICAL INFORMATION (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureFinancingArrangementsAndLongTermDebtNarrativeDetails" id="DisclosureFinancingArrangementsAndLongTermDebtNarrativeDetails">
        <link:definition>99941001 - Disclosure - FINANCING ARRANGEMENTS AND LONG-TERM DEBT - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureSubsequentEventsDetails" id="DisclosureSubsequentEventsDetails">
        <link:definition>99941101 - Disclosure - SUBSEQUENT EVENTS (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureRevenue" id="DisclosureRevenue">
        <link:definition>995210501 - Disclosure - REVENUE</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureAcquisitionTables" id="DisclosureAcquisitionTables">
        <link:definition>99930403 - Disclosure - ACQUISITION (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureRevenueTables" id="DisclosureRevenueTables">
        <link:definition>99930503 - Disclosure - REVENUE (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.informationsg.com/role/DisclosureRevenueContractBalancesDetails" id="DisclosureRevenueContractBalancesDetails">
        <link:definition>99940501 - Disclosure - REVENUE - Contract Balances (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:linkbaseRef xlink:type="simple" xlink:href="iii-20260630_pre.xml" xlink:role="http://www.xbrl.org/2003/role/presentationLinkbaseRef" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" />
      <link:linkbaseRef xlink:type="simple" xlink:href="iii-20260630_cal.xml" xlink:role="http://www.xbrl.org/2003/role/calculationLinkbaseRef" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" />
      <link:linkbaseRef xlink:type="simple" xlink:href="iii-20260630_def.xml" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" />
      <link:linkbaseRef xlink:type="simple" xlink:href="iii-20260630_lab.xml" xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" />
    </xsd:appinfo>
  </xsd:annotation>
  <xsd:import namespace="https://xbrl.org/2023/calculation-1.1" schemaLocation="https://www.xbrl.org/2023/calculation-1.1.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/ecd/2026" schemaLocation="https://xbrl.sec.gov/ecd/2026/ecd-2026.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/dei/2026" schemaLocation="https://xbrl.sec.gov/dei/2026/dei-2026.xsd" />
  <xsd:import namespace="http://fasb.org/us-roles/2026" schemaLocation="https://xbrl.fasb.org/us-gaap/2026/elts/us-roles-2026.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/stpr/2026" schemaLocation="https://xbrl.sec.gov/stpr/2026/stpr-2026.xsd" />
  <xsd:import namespace="http://www.xbrl.org/dtr/type/2024-01-31" schemaLocation="https://www.xbrl.org/dtr/type/2024-01-31/types.xsd" />
  <xsd:import namespace="http://www.xbrl.org/2009/role/negated" schemaLocation="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd" />
  <xsd:import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd" />
  <xsd:import namespace="http://xbrl.org/2005/xbrldt" schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd" />
  <xsd:import namespace="http://fasb.org/us-gaap/2026" schemaLocation="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd" />
  <xsd:import namespace="http://fasb.org/srt/2026" schemaLocation="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/ecd-sub/2026" schemaLocation="https://xbrl.sec.gov/ecd/2026/ecd-sub-2026.xsd" />
  <xsd:element name="BasisOfPresentationDisclosureAbstract" id="iii_BasisOfPresentationDisclosureAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="BasisOfPresentationDisclosureTextBlock" id="iii_BasisOfPresentationDisclosureTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="FinancingArrangementsAndLongTermDebtDisclosureAbstract" id="iii_FinancingArrangementsAndLongTermDebtDisclosureAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="FinancingArrangementsAndLongTermDebtDisclosureTextBlock" id="iii_FinancingArrangementsAndLongTermDebtDisclosureTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="NumberOfClients" id="iii_NumberOfClients" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <xsd:element id="iii_IssuanceOfTreasuryStockForESPPAndVestedRestrictedStockAwardsAndStockAppreciationRights" name="IssuanceOfTreasuryStockForESPPAndVestedRestrictedStockAwardsAndStockAppreciationRights" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" />
  <xsd:element name="DefinedContributionPlanDateAxis" id="iii_DefinedContributionPlanDateAxis" type="xbrli:stringItemType" substitutionGroup="xbrldt:dimensionItem" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DefinedContributionPlanDateDomain" id="iii_DefinedContributionPlanDateDomain" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element id="iii_BusinessCombinationContingentConsiderationLiabilityAccretion" name="BusinessCombinationContingentConsiderationLiabilityAccretion" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="credit" />
  <xsd:element id="iii_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationRollForward" name="BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationRollForward" nillable="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" />
  <xsd:element id="iii_DeferredIncomeTaxExpenseBenefitAdjustments" name="DeferredIncomeTaxExpenseBenefitAdjustments" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" />
  <xsd:element id="iii_DeferredTaxBenefitExpenseFromStockIssuances" name="DeferredTaxBenefitExpenseFromStockIssuances" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" />
  <xsd:element id="iii_AccountsReceivableAndContractAssetsNet" name="AccountsReceivableAndContractAssetsNet" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="debit" />
  <xsd:element id="iii_IncreaseDecreaseInAccountsReceivableAndContractWithCustomerAsset" name="IncreaseDecreaseInAccountsReceivableAndContractWithCustomerAsset" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="credit" />
  <xsd:element id="iii_StockIssuedDuringPeriodForRsuVestedValue" name="StockIssuedDuringPeriodForRsuVestedValue" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="credit" />
  <xsd:element id="iii_NumberOfClientsFromTop100Enterprises" name="NumberOfClientsFromTop100Enterprises" nillable="true" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" />
  <xsd:element id="iii_AdjustmentsToAdditionalPaidInCapitalAccruedDividendsOnUnvestedShares" name="AdjustmentsToAdditionalPaidInCapitalAccruedDividendsOnUnvestedShares" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" />
  <xsd:element name="IncreaseDecreaseInAccruedLiabilitiesAndOtherLiabilities" id="iii_IncreaseDecreaseInAccruedLiabilitiesAndOtherLiabilities" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="debit" />
  <xsd:element name="PaymentsToAcquireBusinessesExcludingAccruedExcessWorkingCapitalAdjustment" id="iii_PaymentsToAcquireBusinessesExcludingAccruedExcessWorkingCapitalAdjustment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="credit" />
  <xsd:element name="CreditAgreement2023Member" id="iii_CreditAgreement2023Member" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="DebtInstrumentCreditSpreadAdjustment" id="iii_DebtInstrumentCreditSpreadAdjustment" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="DividendsCommonStockCashPaid" id="iii_DividendsCommonStockCashPaid" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="debit" />
  <xsd:element name="Rule10b51ArrangementModifiedFlag" id="iii_Rule10b51ArrangementModifiedFlag" type="xbrli:booleanItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="NonRule10b51ArrangementModified" id="iii_NonRule10b51ArrangementModified" type="xbrli:booleanItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="AutomationBusinessLineMember" id="iii_AutomationBusinessLineMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="ComputerExpense" id="iii_ComputerExpense" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="debit" />
  <xsd:element name="CompensationExpense" id="iii_CompensationExpense" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="debit" />
  <xsd:element name="FactBasedSourcingAdvisoryServicesSegmentMember" id="iii_FactBasedSourcingAdvisoryServicesSegmentMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="DescriptionOfOrganizationAndBusinessOperationsTable" id="iii_DescriptionOfOrganizationAndBusinessOperationsTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="DescriptionOfOrganizationAndBusinessOperationsLineItems" id="iii_DescriptionOfOrganizationAndBusinessOperationsLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="DisposalGroupNotDiscontinuedOperationAdditionalProceeds" id="iii_DisposalGroupNotDiscontinuedOperationAdditionalProceeds" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="debit" />
  <xsd:element name="ThirdPartyCosts" id="iii_ThirdPartyCosts" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="debit" />
  <xsd:element name="MartinoAndPartnersMember" id="iii_MartinoAndPartnersMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="BusinessCombinationAdditionalCashConsideration" id="iii_BusinessCombinationAdditionalCashConsideration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="credit" />
  <xsd:element name="BusinessCombinationDeferredPurchaseConsideration" id="iii_BusinessCombinationDeferredPurchaseConsideration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="credit" />
  <xsd:element name="AccountsReceivableLitigationAmount" id="iii_AccountsReceivableLitigationAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" abstract="false" xbrli:balance="debit" />
  <xsd:element name="AccountsReceivableJudgementInterestRate" id="iii_AccountsReceivableJudgementInterestRate" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="BusinessCombinationAndAssetAcquisitionTextBlock" id="iii_BusinessCombinationAndAssetAcquisitionTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="AssetAcquisitionConsiderationTransferredDeferredConsideration" id="iii_AssetAcquisitionConsiderationTransferredDeferredConsideration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="credit" />
  <xsd:element name="AssetAcquisitionConsiderationTransferredDeferredConsiderationPayablePeriod" id="iii_AssetAcquisitionConsiderationTransferredDeferredConsiderationPayablePeriod" type="xbrli:durationItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="AssetsOfAiMaturityIndexMember" id="iii_AssetsOfAiMaturityIndexMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="DebtInstrumentBasisSpreadOnVariableRateAdjustment" id="iii_DebtInstrumentBasisSpreadOnVariableRateAdjustment" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="O2026Q3DividendsMember" id="iii_O2026Q3DividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="AccruedSubcontractorCostsWriteoff" id="iii_AccruedSubcontractorCostsWriteoff" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="debit" />
</xsd:schema>
